quinta-feira, 26 de março de 2009

Natural resins for varnishing and polishing

The alcohol available to wood finishers in earlier days was often of unknown quality, it was usually distilled from wine or brandy, and may easily have contained up to 50% water, as there was no readily available way of measuring the water content in the alcohol. This water causes the varnish to become cloudy, so it was of more than interest sake to measure accurately the purity of the alcohol used in varnish making. An early method was to put a quantity of gunpowder in a spoon and cover with the alcohol to be used for polishing. This was set alight and if, after the alcohol has burnt off, the gunpowder would ignite, it was counted as pure enough to use, if the powder would not ignite, then it contained too much water and would be discounted from use. Later the use of the hydrometer meant that a careful calculation of the purity and water content could be made.

Some of the basis of varnish is natural resins, differing locations of these resins and their differing inherent nature, was the diference for many styles of polishes and varnishes.

  • Anime is the archaic name for fossil copal resin. Fossil resins are mined from deposits found underground, they are found in areas of prehistoric forest, and as such the resin is virtually exhausted today. The original resin the word anime refers to copal resin and is no longer available, but Kauri resin, from New Zealand, is a certain substitute for the original resin. Kauri resin is a superior quality resin, and makes fine quality varnish, used extensively during the 1800’s as the ingredient in most fine quality varnishes, used in both oil and spirit varnishes.
  • Balsam is a resin collected from coniferous trees such as pine, fir, spruce, balsam, and larch. It was historically considered an inferior ingredient in varnishes, but was used to give the varnish a high gloss. It may be seen to be refered to in old recipes, as chian turpentine (derived from Mediterranean pines), Strasburg turpentine (derived from German fir trees), and Venice turpentine (derived from European larch trees). Balsam should not be confused with modern turpentine, the product that is now sold as turpentine, was called turpentine oil or spirits of turpentine, and is a liquid solvent made from the distillation of pine-tree sap. The balsam that is available today, is called copaiba balsam and Canadian balsam.
  • Benzoin is a resin from the styrax benzoin tree that grows in tropical Asia. It was used in spirit varnishes of the 16th and 17th centuries. It has a pleasant odour that is still faintly recognisable on antiques, and for this reason is often added to classic varnishes to reproduce the characteristic smell. In old formulas, it may well be referred to as Benjamin.
  • Copal , various resins have been called copal, some types of copal can be mixed with oils to make oil varnish, and the copal varnish sold in art supply stores, is an oil-based varnish. The type of copal used in spirit varnishes is called spirit or manila copal. This resin is harvested from the trees of the Agathis genus, and is used as an additive to give toughness to the varnish.
  • Elemi is a soft resin produced by the trees of the Burceraceae family, and is added to varnishes to make them more elastic. In old formulas it may be found to be called allemy, and may be bought in art supply stores.
  • Gum Arabic is a resin produced from the trees of the Acacia genus. It is included in some old formulas for spirit varnish, and also is used by artists as a resist, this can also be bought in art supply stores.
  • Lavender oil is oil distilled from the lavender plant, and first produced during the 1500’s, being very similar to turpentine oil, but that turpentine oil will not mix with alcohol, while lavender oil will. It is used in spirit varnishes to make the varnish level out and smooth more easily, so the brush marks flow out better. It may also be refered to as oil of spike or spike lavender.
  • Mastic is a soft resin that is very clear, with a pale yellow colour that may darken with age, and was used in the past when a pale light-coloured varnish was required or desired. It is harvested from the Pistacia lentiscus tree that grows in the Mediterranean region. The best mastic comes in small drop shaped beads called ‘tears’, these have been harvested while still attached to the tree. The lower grades of mastic have been harvested from the ground, and contain impurities. Mastic can be bought in art supply stores.
  • Rosin is the resin that is left after the balsam from the trees such as pine, fir, spruce, balsam and larch, is distilled to make spirits of turpentine, and like balsam, it was considered an inferior ingredient in varnish, but used to give varnish a high gloss finish. In old formulas it may well be referred to as colophony, when it was derived from the American pine trees, or as greek pitch, when it was derived from the Aleppo pine.
  • Sandarac is a brittle resin, derived from the Alerce tree (Tetraclinus articulate) that grows in the Atlas mountains of North America, and Cypress pine trees (Callistris quadrivalvis), in old formulas, it may be refered to as gum juniper. It was probably the most widely used resin for varnish making, because it is very clear and dissolves easily in alcohol. Since sandarac, used alone, forms a very brittle film, elemi was often added to sandarac varnish to improve its elasticity. Sandarac varnish starts almost colourless, but with age it becomes darker and slightly reddish. The best quality sandarac is harvested while still attached to the tree, and is called ’tears’ of sandarac, the lower grade is harvested from the ground and contains impurities. Sanarac also can be obtained in art stores.
  • Shellac is unique amongst natural resins, since it is produced by insects on a plant. Shellac varies in colour depending on the shellac used. Early varnish formulas used seed-lac, button-lac, or orange shellac, and the varnish produced had an orange or dark brown colour. Seed-lac was considered the best for use in spirit varnish during the 1600’s, and it produced a lighter colour of varnish than the orange shellac. In older formulas, when gum lac is specified, kausmi seed-lac is probably being referred to. When old formulas specify shellac, it is appropriate to use the orange shellac. Lighter coloured shellacs were not available until the late 1700’s, although shellac was used in a limited way for a long time, its dark colour made it less desirable, at a time when finishers were striving for a pale light-coloured finish with the varnish. After lighter forms of shellac became available, it soon became one of the most sort and used components in a spirit varnish.
To give an idea of the different varnishes available to artists during the 1800's. here are some of the types that were sold by colourmen such as Windsor & Newton, Reeves, Roberson and Rowney, from 1800 to 1890.
  • Mastic varnish later called mastic varnish for varnishing pictures 1835
  • Copal varnish later called copal (oil) varnish 1835
  • Copal spirit varnish later called white copal spirit varnish 1856
  • Fine picture copal varnish 1835
  • White spirit varnish 1835
  • Brown spirit varnish 1835
  • Transfer varnish 1835
  • Double mastic varnish later called doble strength for Magilp 1840
  • White lac varnish also called lac varnish 1840
  • Crystal varnish later refered to as crystal or map varnish 1840
  • Caustic or transfer varnish 1840
  • Raising varnish 1840
  • Roberson's fixing liquid for chalk and pencil drawings, in bottles 1840
  • Grecian varnish 1840
  • Field's white lac varnish 1870
  • Photographic varnish for negatives 1870
  • Amber varnish light 1883
  • Amber varnish dark 1883
  • Soehnée varnish 1883
  • Soehnée Frére's varnish for pictures 1890
  • Soehnée Frére's varnish for paper and etc. 1890
  • Picture copal varnish 1890
  • Paper varnish 1883
  • Vibert's vernis á retoucher 1896
  • Vibert's vernis á tableaux 1896
  • Mastic varnish No 2 for pictures 1896
  • Rowney's picture glaze 1907.

Varnishes:Till Your Art and work may Call for its Assistance

Spirit and oil varnishes have a long history, the word varnish is often applied to the brushed on, thicker type of boiled finish, whilst it’s shellac base may well be called polish. Here we have two types of varnish, the spirit based and the oil based varnishes.

spirits of wine - rectified ethyl alcohol
ethanol, ethyl alcohol, fermentation alcohol, grain alcohol - the intoxicating agent in fermented and distilled liquors; used pure or denatured as a solvent or in medicines and colognes and cleaning solutions and rocket fuel; proposed as a renewable clean-burning additive to gasoline

shel·lac also shel·lack .n.
1. A purified lac in the form of thin yellow or orange flakes, often bleached white and widely used in varnishes, paints, inks, sealants, and formerly in phonograph records.
2. A thin varnish made by dissolving this substance in denatured alcohol, used to finish wood.
3. An old phonograph record containing this substance, typically played at 78 rpm.

seed lac - granular material obtained from stick lac by crushing and washing
lac - resinlike substance secreted by certain lac insects; used in e.g. varnishes and sealing wax
stick lac - lac in its natural state as scraped off twigs and dried.

Spirit Varnish.

This is a varnish that has the natural resins dissolved in alcohol, and shellac is the now most commonly used spirit varnish, although in the past there were many types of spirit varnishes in use. They can be be a very hard and resistant finish, and their clarity can enhance the wood with a fine finish, but do suffer from moisture penetration and marking, being also less resistant to common alcohol and spirit use.

Before modern finishes were developed, the spirit varnish and polish, was favoured for its clarity and high degree of fineness in the finish, although the harder varnishes had a tendency, with time, to become very brittle and develop fine crazing over the surface. There are hundreds of recipes for all types of varnish, here I will give some idea of how they were made, in the Dr,Ure’s Dictionary of 1840, he writes these recipes;

White Hard Spirit Varnish, or the white hard spirit of wine varnish,

Put 5 pounds of gum sandarac into a 4 gallon tin or bottle, with 2 gallons of spirits of wine, 60 over proof (too strong to drink) and agitate until all is dissolved, exactly as is directed for the best mastic varnish, recollecting, if washed glass is used, that it is convenient to dip the bottle containing the gum and spirits into a copper-full of hot water every 10 minutes- the bottle to be immersed for only two minutes at one time- which will greatly assist in the dissolving of the gum; but, above all, be careful to keep a firm hold of the cork of the bottle, otherwise the refraction will drive the cork out with the force of a shot, and perhaps set fire to the place ! The bottle, every time it is heated, ought to be carried away from the fire (remember this is alcohol inside) and the cork should be eased a little, to allow the now rarefied air to escape: then driven tight, and the agitation to be continued in this manner until all the gum is properly dissolved; which is easily known by having an empty tin can in which to pour the vanish, until near the last, which is to be poured into a gallon measure. If the gum is not all dissolved, return the whole of the mixture into the 4 gallon tin/bottle, and continue the agitation until it is ready to be strained, when every thing ought to be quite ready,and perfectly clean and dry,as oily tins, funnels, strainers,or any thing damp, or even cold weather, will chill and spoil the varnish. After it is strained off, put into the varnish 1 quart of very fine turpentine varnish, and shake and mix the two well together. Spirit varnishes should be kept well corked: they are fit to use the day after they are made.

Brown Hard Spirit Varnish.

Brown hard spirit varnish is made by- putting into a bottle 3 pounds of gum sandarac, with 2 pounds of shellac ( shell-lac) and two gallons of spirits of wine, also 60 over proof; proceeding exactly as before directed for the white hard varnish, and agitating it when cold, which requires about 4 hours of time, without any danger of fire; whereas, making any spirit varnish over heat is attended with a degree of danger. No spirit varnish ought to be made near fire or candle light. When this brown hard is strained, add 1 quart of turpentine varnish, and shake and mix well: next day it is fit for use.

French White Spirit varnish.

The following are reckoned to be good French recipes for varnishes:

White spirit varnish – Sandarac, 250 parts, mastic in tears, 64; elemi resin, 32; turpentine (vernice), 64; alcohol, of 85 per cent,1000 parts by measure. The turpentine is to be added after the resins are dissolved. This is a brilliant varnish, but not so hard as to bear polishing.

For large quantities of the spirit varnish, Dr Ure recommends the following:

“ When large quantaties of spirit varnish are to be made, a common still, mounted with its capital and worm, is the best vessel employed for containing the materials, and it is placed in a steam or water bath. The capital should be provided with a stuffing-box, through which a stirring-rod may pass down to the bottom of the still, with a cross piece at the end, and a handle or winch at the top. After heating the bath till the alcohol boils and begins to distil, the heat ought to be lowered, and the solution may continue to proceed in an equable manner, with as little evaporation of the spirits as possible. The operation may be supposed to be complete when the rod is easily turned round. The varnish must then be passed through a silk sieve of proper fineness; then filtered through porous paper, or allowed to clear leisurely in stone jars. The alcohol which has come over should be added to the varnish, if the just proportions of the resins have been introduced at first”.

If I can get hold of the software for text recognition, I have a large number of recipes, in many books, and covering many periods of history, and it would be good to post them on the net. However the work load to simple read and then rewrite these is rather greater than I would like to undertake at the moment, text recognition would allow me to scan and copy into word, direct, and then also give me the opportunity to translate into other languages and also copy and translate Italian and Spanish reference into English.

A Treatise of Japaning and Varnishing; Stalker and Parker, 1688.

This excerpt gives recipes that have not changed over the three centuries that have now passed since the writing of their treatise.

“Take one gallon of good spirit, and put it into as wide a mouthed bottle as you can procure, for when you should afterwards strain your varnish, the Gums in a narrow mouthed bottle mat stick together, and clog the mouth, so it will not be easie task to sparate or them them out. To your spirits add one pound and a half of the best seed-lac, let it stand the space of 24 hours, or longer, for the gum will be better dissolved, observe to shake it very well, and often, to keep the Gums from clogging or caking together. When it hath stood for some time, take another bottle of the same bigness, or as many quart-ones that will take your varnish; and your strainer and flannel made as foresaid in the book. Fasten it to a tenter hook ( it was the custom for butchers to hang meat and game on a hook, until the meat relaxed and became more tender, thus getting the name of tender or tenter hook) against a wall, or some other place that is convenient for straining it, in such a posture, that the end of your strainer may almost touch the bottom of your tin-tunnel, which is supposed to be fixed in the mouth of your empty bottle, on purpose to receive your strained varnish. Then shake your varnish well together, and pour or decant into your strainer as much as it will conveniently hold, only be sure to leave room for your hand, with which you must use to squeeze out the varnish, and when the bag by so doing is almost dry, repeat it, till all your strainer is being almost full of dregs of the Gums, shall (the moisture being all pressed out) be required to be discharged of them; which faeces or dregs are of no use, unless to be burnt, or fire your chimney. This operation must be continued, till all your varnish is after this manner strained; which done, commit it to your bottles close stopt, and let it remain undisturbed for two or three days, then into another clean empty bottle pour off very gently the top of your varnish, so long as you oberve it to come clear, and no longer, for as soon as you observe it to come thick, and muddy, you must by all means desist: and again, give it time to rest and settle, which twill do I a day or two; after which time you must attempt to draw off as much of you fine varnish, and having so done you may lay it up, till your art and work may call for its assistance. Tis certain, that on any emergency or urgent occasion you may make varnish in less time than 24 hours, and use it immediately, but the other I recommend as the best and more commendable way: besides, the varnish which you have from the top of the bottles first poured off, is of extraordinary use to adorn your work and render it glossy and beautiful. Some artists, through haste or inadvertency, scruple not to strain their varnish by fire or candle-light; but certainly day-light is much more proper, and less dangerous; , for should your varnish through negligence or chance take fire, value not that loss, but rather thank your stars that your self and work-house have escaped. Should I affirm, that the boiling the Lacker and Varnish by the fire, were very prejudicial to the things themselves, I could easily make good the assertion; for the y are as well and better made without that dangerous element, which any after this caution will undertake, they may feeling assure themselves that tis able to spoil the experiment and operator. On the other hand, no advantage or excellence can accrue either to Lacker or Varnish, especially when, as some of them do, tis boiled to such great a height, that this Aetna is forced to throw out its fiery eruptions, which for certain consume the admiring Emperdocles, who expires a foolish and negligent Martyr; and it would almost excite one’s pitty, to see a forward and ingenious undertaker, perish in the beginning of his enterprise; who might have justly promised to erect a noble and unimitable work of art, as a lasting monument of his fame and memory: but (unhappy man) his beginning and his end are of the same date; his hopes vanish, or frightfully represented in a Puppet-shew, or on a sign-post.

To make shell-Lac varnish.

Whosoever designs a neat, glossy piece of work, must banish this as unserviceable for, and inconsistent with, the rarities of our art. But because tis commonly used by those that employ themselves in varnishing ordinary woods, as olive, Walnut, and the like, tis requisite that we give you directions for the composition of it, and if you conveniency or fancy lead that way, you may be supplied with materials for the performance. Having therefore in readiness one gallon of the best spirit, add to it one pound and a half of its best Shell-lacc. This mixture being well stirred and shaked together, should stand about 24 hours before tis strained: You might have observed, that the former varnish had much sediment and dregs; this on the contrary has none, for it wholly dissolves, and is in consequence free from all dross or faeces, tis requisite however to strain it, that the sticks and straws, which are often in the Gum, may by this percolation be sparated from the varnish. But although this admits of no sediment, and in this case differs from the aforementioned varnish, yet tis much inferior also to it in another respect; That this will never be fine, clear and transparent, and therefore twill be lost labour to endeavour, either by art or industry, to make it so. This shall advantage however doth arise, that you need not expect or tarry its perfection, for the same minute that made it, made it for use. This, has I hinted before, is a fit varnish for ordinary work that requires not a polish, and look well for the present, yet like the handsome lady’s beautiful face, it hath no security against the injuries of time; for but for a few days will reduce it to its native mist and dullness. Your common varnish-dawbers frequently use it , for tis doubly advantage to them, having greater body than the Seed-lacc, less labour and varnish goes to the perfecting of the work, which they carelessly slubber over, and if it looks tolerably bright till tis sold, they matter not how dull it looks afterwards; and lucre only being designed, it can compass that, farewell and admiration. Poor insufficient pretenders, not able to make their work more apparent, or more lasting than their knavery ! And tis pretty to think that this same misty cloak will not cover the fraud or the impostor! That the first should be a foil to the second, and the dull foggy work serve only to set off the knavish artist in the most lively colours ! But to conclude, if with a pint of this varnish you mix two ounces or more of Venice-turpentine, it will harden well, and be a varnish good enough for the inside of drawers ( remember that it is not necessary to use good hard varnish in every part of a piece of furniture, a lesser quality can surfice for areas of less wear), frames of tables, frames of chairs, stools, or the like. Painters lacker (lacquer) made also from this varnish, and something of a larger quantity of turpentine put to it, serves very well for the lackering of coaches, house, signs, or the like, and will gloss with very little heat, and, if occasion be, without”

segunda-feira, 23 de março de 2009

Use of tree Oils. Varnish and Berenice

> The word "varnish" comes from Latin vernix meaning odorous resin, which etymology comes from Greek Berenice, ancient name of modern Benghazi in Libya, credited with the first use of varnishes and where resins from the trees of now-vanished forests were sold. Berenice comes from the Greek words phero (to bring) + nike (victory).

Berenice II (267 or 266 BC - 221 BC), was the daughter of Magas of Cyrene and Queen Apama, and the wife of Ptolemy III Euergetes I, the third ruler of the Ptolemaic dynasty of Egypt.

During her husband's absence on an expedition to Syria, she dedicated her hair to Aphrodite for his safe return, and placed it in the temple of the goddess at Zephyrium. The hair having by some unknown means disappeared, Conon of Samos, explained the phenomenon in courtly phrase, by saying that it had been carried to the heavens and placed among the stars. This story is parodied in Alexander Pope's The Rape of the Lock.

The predecessor of the modern city Benghazi was refounded by her and received her name: Berenice.

After the marriage of Ptolemy III to Berenice, daughter of the Cyrenean Governor Magas, around the middle of the third century, many Cyrenaican cities were renamed to mark the occasion. Euesperides became Berenice and the change of name also involved a relocation. Its desertion was probably due to the silting up of the lagoons; Berenice, the place they moved to, lies underneath Benghazi's modern city centre. The Greek colony had lasted from the sixth to the mid-third centuries BC.

The asteroid 653 Berenike, discovered in 1907, is also named after Queen Berenice.

The name Coma Berenices or Berenice's hair, applied to a constellation, commemorates this incident. Callimachus celebrated the transformation in a poem, of which only a few lines remain, but there is a fine translation of it by Catullus. Soon after her husband's death (221 BC) she was murdered at the instigation of her son Ptolemy IV, with whom she was probably associated in the government.

The Candlenut (Aleurites moluccanus), is a flowering tree in the spurge family, Euphorbiaceae, also known as Candleberry, Indian walnut, Kemiri, Varnish tree or Kukui nut tree.

Its native range is impossible to establish precisely because of early spread by humans, and the tree is now distributed throughout the New and Old World tropics. It grows to a height of 15–25 metres (49–82 ft), with wide spreading or pendulous branches. The leaves are pale green, simple and ovate, or trilobed or rarely 5-lobed, with an acute apex, 10–20 centimetres (3.9–7.9 in) long. The nut is round, 4–6 centimetres (1.6–2.4 in) in diameter; the seed inside has a very hard seed coat and a high oil content, which allows its use as a candle (see below), hence its name.

Koelreuteria paniculata (Goldenrain tree, Pride of India or China tree) is a species of Koelreuteria native to eastern Asia, in China and Korea.

It is a small to medium-sized deciduous tree growing to 17 m tall, with a broad, dome-shaped crown.

The leaves are pinnate, 15-40 cm (rarely to 50 cm) long, with 7-15 leaflets 3-8 cm long, with a deeply serrated margin; the larger leaflets at the mid-point of the leaf are sometimes themselves pinnate but the leaves are not consistently fully bipinnate as in the related Koelreuteria bipinnata.

The flowers are yellow, with four petals, growing in large terminal panicles 20-40 cm long. The fruit is a three-parted inflated bladderlike pod 3-6 cm long and 2-4 cm broad, green ripening orange to pink in autumn, containing several dark brown to black seeds 5-8 mm diameter.

Walnuts (genus Juglans) are plants in the family Juglandaceae. They are deciduous trees, 10–40 meters tall (about 30–130 ft), with pinnate leaves 200–900 millimetres long (7–35 in), with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts (Pterocarya) but not the hickories (Carya) in the same family.

The 21 species in the genus range across the north temperate Old World from southeast Europe east to Japan, and more widely in the New World from southeast Canada west to California and south to Argentina. The Latin name, Juglans, derives from Jovis glans, "Jupiter's acorn": figuratively, a nut fit for a god.

The word walnut derives from Old English wealhhnutu, literally "foreign nut", wealh meaning "foreign" The walnut was so called because it was introduced from Gaul and Italy. The previous Latin name for the walnut was nux Gallica, "Gallic nut".

In some countries immature nuts in their husks are preserved in vinegar. In England these are called "pickled walnuts" and this is one of the major uses for fresh nuts from the small scale plantings. In Armenian cuisine, walnuts are preserved in sugar syrup and eaten whole. In Italy, liqueurs called Nocino and Nocello are flavoured with walnuts, while Salsa di Noci ("Walnut Sauce") is a pasta sauce originating from Liguria. In Georgia, walnuts are ground along with other ingredients to make walnut sauce.

The nuts of all the species are edible, but the walnuts commonly available in shops are from the common walnut, the only species which has a large nut and thin shell. A horticultural form selected for thin nut shells and hardiness in temperate zones is sometimes known as the 'Carpathian' walnut. The nuts are rich in oil, and are widely eaten both fresh and in cookery. Walnut oil is expensive and consequently is used sparingly; most often in salad dressing. Walnuts are also an excellent source of omega-3 fatty acids, and have been shown as helpful in lowering cholesterol. They need to be kept dry and refrigerated to store well; in warm conditions they become rancid in a few weeks, particularly after shelling. Oil paint often employs walnut oil as an effective binding medium, known for its clear, glossy consistency and non-toxicity.

Walnuts are heavily used in India. In Jammu, India it is used widely as a prasad (offering or gracious gift) to Mother Goddess Vaisnav Devi and, generally, as a dry food in the season of festivals such as Diwali.

Cleansing and polishing: Walnut shells are mostly used to clean soft metals, fiberglass, plastics, wood and stone. This environmentally friendly and recyclable soft grit abrasive is well suited for air blasting, de-burring, de-scaling, and polishing operations because of its elasticity and resilience. Uses include cleaning automobile and jet engines, electronic circuit boards, and paint and graffiti removal. For example: In the early days of jet transportation, crushed walnut shells were used to scour the compressor airfoils clean, but when engines with air cooled vanes and blades in the turbine started being manufactured this practice was stopped. The problem being that the crushed shells tended to plug up the cooling passages to the turbine, resulting in turbine failures due to overheating.

* Oil well drilling: The shell is used widely in oil well drilling for lost circulation material in making and maintaining seals in fracture zones and unconsolidated formations.

* Flour made from walnut shells is widely used in the plastics industry.

* Paint thickener: Walnut shells are added to paint to give it a thicker consistency for "plaster effect" ranges.

* Explosives: Used as a filler in dynamite.

* Cosmetic cleaner: Occasionally used in soap and exfoliating cleansers

Walnut husks are often used to create a rich yellow-brown to dark brown dye that is used for dyeing fabric and for other purposes. When picking walnuts, the husks should be handled wearing rubber gloves, to avoid dyeing one's fingers, as the dye does not require a mordant.

Walnut as wildlife food plants

Walnuts are used as food plants by the larvae of some Lepidoptera species.

* Brown-tail (Euproctis chrysorrhoea)

* the Coleophora case-bearers C. laticornella (recorded on J. nigra)

and C. pruniella.

* Common Emerald (Hemithea aestivaria)

* Emperor Moth (Pavonia pavonia)

* The Engrailed (Ectropis crepuscularia)

* Walnut Sphinx (Amorpha juglandis)

In addition, the nuts are a popular snack among woodland creatures, specifically mice and squirrels.

sábado, 7 de março de 2009

Re Lining of paintings

Having spent a considerable time copying this reference material, from one of my books, in order to then, translate into Portuguese for a friend, I thought that it would benefit from a greater airing to a wider public, but I will publish it in English, as it will be for a greater benefit.
I have a number of books that are of varying degrees of complexion, this is from a compilation of the history of conservation and historical letters on the same subject, that was published by the Getty Foundation, they have, along with the Courtauld Foundation, produced a vast and incredibly useful selection of books and articles, all of merit. This is from the Issues in the Conservation of Paintings(2004). it is an account of the lining process but by no means an account from which to base your own work, there are many more recent books that are very detailed and helpful to the restorer, but this is of interest and worthy of a read.

The Lining Cycle by Westry Percival-Scott ..1974

The early 19 century impregnation methods aiming at strengthening a weakened canvas, were almost entirely superseded by the lining of paintings using a new canvas support. Francois-Xavier de Burtin’s treatise on pictures written in 1808 at Brussels, descriptions and criticisms of lining methods of the time are particularly valuable. Lining can be demonstrated to be of value to a painting if it is well carried out. “But” he writes, “I must say also that many persons undertake it who acquit themselves so ill, that pictures come out of their hands as rough, and with the breaks and cracks as visible, as when they were put into them, or if they appear at first more united and in better condition after the lining, their old defects are not long in reappearing; they peel off, or shrink, blister, show as many disagreeable lines as there have been joining in the sheets of paper with which they had been covered during the operation, exhibit all the traces of the frames, and however little the season may be a damp one, it is not uncommon to find a villainous mould appearing upon them from the bad size which had been employed, and which even shows itself through the varnish At other times the use of size too dry and hard renders the picture stiff and brittle, and causes them almost to bend the stretcher. It is very lucky indeed if workmen so audacious and unskilful do not ruin the picture, by scorching it by using irons that are too hot, or by raising pieces of it from the ground; or destroy the glazing by the employment of mordents without sufficient caution, in order to remove the yellowish mould which is the necessary consequence of there having burned the varnish, and often the colours themselves, by the application of too much heat. In truth, the dangers to be encountered are so apparent to me, that I know not how to advise amateurs that have pictures to line. Whether from ignorance or stupidity, I have seen with regret during my travels that most liners neglect the proportions and depart from the process employed in Paris (then thought to be the centre of excellence for picture restoring) by artisans more justly famous in this branch. These last, in place of lining the pictures on their own stretchers by means of very hot irons, always do it, so far as their size will permit, on false stretchers, in such a manner that they can work them from two sides; and they supply the place of the great heat used by the others, by use of heavier irons (generally a 15 lb weighted iron was used), longer continual labour, and more frequent renewal of paper. They do not spare any exertion either, to obtain a paste and a ground size that shall be perfect, and a fine canvas without knots, thus every picture coming out of their hands united like a mirror, and always remains so.”

In a later note he says, “Their workshops present an imposing aspect from the immense tables, the pulleys, the smoothing irons of all weights and sizes, and the other implements, which announce at the first glance a substantial establishment, and inspire one’s confidence.” He goes on to praise the qualities of Monsieur Foucque, one of the liners for the Musee de Paris, “that I owe him the return of making this public acknowledgment of his talents. The pictures that come out of his hands are so united like glass, without any vestiges of old creases, or marks of the facing paper, which is renewed four or five times if there be occasion. In place of burning the colours, as so many others do, he employs irons with so little heat, that he is obliged to supply the place of heat by using them of much greater weight, and by applying more labour.”

De Burtin goes on to say that the two major causes for bad lining are the over heating of the irons or the bad quality of the composition for fixing the old canvases to the new. “ A most certain occasion for failure in lining” he says, “results from the size used being too strong, or from the mixture of other ingredients which attract moisture which, especially in Winter, attract mould….. Lastly from the use of certain mixtures for this purpose liable to be affectected by variations in the atmosphere,” he recommends, “ a composition which Monssieur Fontaine of Paris has prepared.”

The composition is made by taking any given quantity of jelly (cold size) made from parchment, sheep’s skin, or other skins, by boiling, to which add an equal quantity of water, and a fourth part of the same quantity of rye meal. The whole is heated, and used warm. The jelly or size made from the skins is the same as that used by gilders, except that it ought to be only half as strong.

The consistency should be that when cold the jelly will support vertical a spoon placed in it.

Here are two recipes given:

  1. Venice Turpentine….1 lb

White resin………….0.5 lb

1 stone of flour……..

adding thinned glue to give consistency

  1. 2 quarts of paste

0.5 pint of made glue

0.5 do Venice Turpentine

2 tablespoons of boiled linseed oil

1 table spoon of Paris White.

The editor of the 1845, English edition of Burtin’s treatise makes the following note, ”The following two recipes for size are, it is believed, used by some of the best London liners, for fixing pictures on new canvas.”

Fielding, writing in 1847 in London, had no hesitation in advising that paintings should be lined. “In almost all cases, if the picture has not already been lined, it would be best that this should be done before any other operation takes place; and it is so much better performed by those that make it their business, that we recommend none that have the opportunity of getting it done in London, or other places where there are persons accustomed to its management.” He then goes on to recommend a method which, in our eues, would only result in extreme distortion and produce an adhesive which would be extremely difficult to remove. This is very typical of linings of this period.

“Take the old picture from the stretcher frame and lay it on a perfectly flat surface, as a table, or a large drawing board, something larger than the picture, the front of the picture upwards; lay on the surface of the picture a sheet of paper covered with thin paste, particular if the picture is broken in the paint, or has holes in it. Afterwards take some thin glue size, and with it make a paste of wheat flour; this by some is used moderately warm; others prefer it cold, and at least one day old; perhaps the former would be considered the best. The picture is made something less than the new stretcher frame on which it will have to be placed when ready, by cutting a little of its edge; and the canvas or unbleached cloth, which is to constitute the lining, must be so much larger than the picture as to leave a sufficient quantity to admit it being nailed on to the new stretching frame. The picture now must be laid on the table, or level board, front downwards, the table or board having previously been made a little damp with a sponge; this will make it adhere to the table in some measure; but if it be wished that the picture be immoveable, as in the process of transferring from an old cloth to a new one, described here in another place, the best mode is to have the paper that is attached to the front of the picture something larger than the picture, so that the edges may be made fast to the table with glue or paste. The back of the picture is next to be covered with paste, of a very strong copal varnish, or with a cement, or a kind of glue, made from a good cheese that has been well pounded in a mortar, and then washed with warm water to carry off the most soluble part of it. The substance which is left can only be dissolved if beaten up with lime water, to a paste again in a mortar, to which it is added gradually, until it become sufficiently diluted for use. But wich ever of the above may be used, it must be well brushed into the back of the picture, and the lining well pressed down on to it, by pressing the hand down on it in every direction. The outer edges of the lining, are to be nailed to the table with a great number of small tacks, so drawing the canvas as tight as possible in every way; afterwards a piece of wood, with a rounded edge, is passed over the lining with a tolerable hard pressure, to perfect the adhesion of the picture.

“The glue made from cheese is said to have valuable property of being, when dry; perfectly incensible to any wet or moisture. When the lining is so far dried, that the paste or glue, which has penetrated through, will not stick to the iron, it is to be passed all over with a heated iron, moderately hot, and the greatest care must be taken that the hand does not stop for an instant, or the mark of the iron will be so impressed on the painting that nothing will obliterate it. The picture is now ready to be nailed on to a new stretching frame.

The combination of washed cheese solids and lime water produced an irreversible casein glue of a traditional type. At the same time it was introduced into the manufacture of commercial painting grounds, which in turn led into the embrittlement of many of the paintings of this period.

Crisis in Venice

The following of the Venetian oil technique in the 16th and 17th centuries when the confidence in the capabilities of the method encouraged the painting and production of massive ceiling pieces and the painting of a size far beyond the physical capabilities of the support, this period can be used by us as a useful landmark in the sequence of deterioration which I have called the lining cycle. Glues and grounds of the type described by Vasari in 1550 have only got a period of limited life. Consolidation of the paint layers by impregnation with glue would only produce factors which would cause in time further deformation. The impregnation techniques that were used up to 1670, when lining at last came into common practice might have strengthened the paint layers and consolidated the canvas, but would have done little to prevent the subsequent mechanical breakdown which would come in the form of tears and the falling away of the canvas from the top stretchers. A reasonable estimate of the period of time required for this kind of weakness would be anything between 100 to 150 tears would be the outside limit before a picture would have to receive either strip lining or attention for structural weakness. Thus, if we look at the period of Venetian history from the beginning to the end of the 18th century, we will find an historical landmark of immense importance in the history of conservation.

I will now take my descriptions of these events from extracts from an original manuscript by Signore Giovanni Okelly Edwards of Venice, 1833, The author of this manuscript was the only son of Signore Pietro Edwards, who practised restoration in Venice under the ventian republic and subsequently under the Austrian government. He died in 1821 at the age of 76. In a paper entitled, “On the Restoration of the Royal Paintings under the Ventian Government” he refers to the number of reports on the poor condition of the paintings between 1725 and 1775, no less than 751 reports were prepared at this time. All mentioned the decay of the pictures and earnestly called the attention of the public to the urgent necessity of repairing the greater part of them. A report prepared for the Society of Painters in 1727 showed the number of paintings requiring restoration at that time amounted to 20. It was, however, thought Signor Edwards, “very fortunate that the Government should have acted with great circumspection until the year 1777 in consenting to the general and universal restoration of all the royal paintings, because the art of repairing paintings damaged by the time had not then attained perfection.” By the 1770’s the situation had changed radically and in the years to follow, hundreds of paintings received restoration treatment. Signor Edwards lists 41 paintings by Jacomo Tintoretto, 11 by Bassani, and a few of Titian; in all 405 pictures were restored between the years 1779 and 1785 under the direction of the Venetian Senate, who entrusted the undertaking of this general restoration of the President of the College of Painters. These pictures were contained in 32 public buildings in the district of St Marks and the Rialto, after which 270 more were restored between the last mentioned period and the year 1788 under the direction of the same person, making a total of 675 public paintings restored out of 1187.

The pictures were divided into classes and the sums of money for the restoration were based on square footage. “The pictures of first class that were restored, computed by the Italian square feet, comprised an area of 6,458 sq ft and 26 inches, of the second class 6,407 sq ft and 5 inches in total in square feet 12,865 and 31 inches. 26 artists acting as restorers were retained in public service during this period of restoration, and they worked under a Royal Inspector of Pictorial Restorations and continued to work in Venice until 1779, in restoring 82 further pictures under the Austrian Government. This restoration continued, and when Mrs Merrifield met Edwards in 1833, she had an opportunity of seeing one of the canvases by Paulo Veronese which had been removed from the ceiling. “Had an opportunity of closely examining one of these works which had been removed from the ceiling for the purpose of being repaired. The picture had been lined, but much of it had absolutely decayed and there were large blanks on the new canvas. The ground of the picture was extremely thin, and was not visible; the paintings were much worn in places and some if it had scaled off.”

When Mrs Merrifield was visiting Venice and was going through the papers of Signor Pietro Edwards, Director of Restorations, she came across one contract for the restoration of a picture by Signore Floriani. The painting in question was the Assumption of the Virgin by Titian, formally in the church of the Friary, and now in the Academia. The date of this document ascertained that the paste used for the lining the picture was composed of flour paste, Flanders glue and Ox gall, the use of the later ingredient was to preserve the paste from the attack by insects.”

“ The method of pressing freshly lined pictures pursued by Signore Edwards differed from that practised in this country(England). The process was described to me by his son. It was as follows:

The face of the picture being secured by pasting paper over it, it was laid on the polished Venetian floor, or, as it is called ‘terrazzo’ and the lining was fixed to it. Hot sand was then laid all over it, beginning always in the middle of the picture, whence the sand gradually spread to the edge, and the picture was covered to a certain height. By this means, the air was pressed out from between the canvas and the picture, and an equal degree of warmth and pressure was communicated at the same time to the whole surface, much more safely and effectively than with a hot iron.”

Glue has continued to be used as a consolidant for flaking paint from the 17th century to the present day, when it is an everyday occurance in many Italian and Russian studios. In “Il restauratore dei Dipinti,” published in Milan 1866, Signore G Secco Suardo describes a colletta for consolidating the painting.” This is recipe No.8. “Take 12 parts the glue in transparent flakes, which is improperly called ‘Colla di Pesce’ (fish glue) while it is only a strong glue of the most refined sort, which is used in cooking for gelatine, and dissolve it in 12 parts of water. Put in 4 parts of molasses, mixing it with hot water, as much as necessary to reduce it to the necessary fluidity, which varies according to the case, but on the average it can be of the consistency of milk, but if instead you want to keep it, you should add one part of good white vinegar, then, in a glazed earthenware, very spread out, keep it in a milk warmth so that it can evaporate without fear of burning and condense like a ‘vischio’ (mistletoe. sticky !) “He goes on to say, “Monsieur Merimée teaches that animal glue will tolerate an eight of oil, but does not announce how to add the oil to the glue would be that when there is little water in it. Hence, having just obtained the colletta, as indicated in recipe No. 8, unite with it a little at a time, nut oil in the proportion of one part to eight of glue, weighing it before it is melted, mixing it very carefully so that the two substances are perfectly incorporated.” For his lining mixture, Secco Suardo uses heavier glue. This recipe is No.12. “Take flour of linseed, one part, put it in a casserole and unite it in the usual way with 24 parts of water, put in also two parts of strong glue, and boil it for half an hour. Take it from the fire; put it in a vessel three parts of corn flour and the same of rye flour, put into it a little at a time, the mixture in the casserole, manipulating it qith a spatula, so that it is well mixed, then pass it through a sieve, pressing it.”

“Throw the remains from the sieve, away, place that which passes through into the casserole, and that on the fire, and stirring constantly bring it to the boil; and when it is well cooked, that is to say, when it has boiled for a few minutes, take it off, for the glue is made, except that, before it cools, put in it also one part of molasses, so that it remains sufficiently elastic. It is very useful and I recommend it.”

Glue mixtures of the type here described by Secco Suardo are still used today. That has the advantage of being glues of low cohesion strength which limit the stress exerted on the painting canvas, and which make the eventual removal of the lining canvas comparatively easy.

The ever-increasing rate of decay of pictures in the late 18th and early 19th centuries, is reflected in the rise of the number of restorations recorded, and in the wave of interest shown in lining and transfer techniques. The attention of the art world was gripped by the amazing technical feats of transfer carried out in France by Hacquin and Picault. Although almost all of these methods were based on the use of animal glues and casein, and on marouflage using pigment/oil cements, the first experiments with wax, both for lining and blister laying, had been carried out in the mid 18th century. But the earliest record of wax as a firmly established lining adhesive is not until 1858, when it was in use by Carbonelle of Brussels for this purpose. A detailed account of this period in the history of restoration may be found in Marijnissen

Origins and development of the Use of Wax.

Much of the enthusiasm for the use of wax impregnation springs from the work of Count Caylus, who devised a new method of painting in encaustic pictures by first applying paint, onto to a canvas that had first been coated with beeswax. On completion, the painting was heated in front of a fire, and the wax was allowed to penetrate into the unlocked colours. The burst of interest in this unusual method might well have waned had it not been for an enthusiastic painter, Mr. Muntz, who carried out a series of exhaustive experiments, using the Caylus principle proving the value of wax as a protective coating and consolidate. Mr. Muntz carried out his first tests in 1757, and in 1760 he gave a description of the results of his experiments. “I had all the colours used in oil painting carefully ground with water at Mr. Sandys colour merchant, and from these colours, I composed 90 various tints of each a two ounce galley pot full, tempered with water, I left them well screened from dust to dry, divided each into four equal parts; two of each set by for comparative use, the other two used as follows

One part tempered with water, the other with the finest nut oil according to custom, each painted over a space of 6” x 2”.

The encaustic ones brought to the fire as instructed, each piece of cloth cut into five equal parts .

  1. One of each in the open air, exposed to sun, dew, wind and rain.
  2. One of each nailed to wall of cellar.
  3. One of each nailed to kitchen ceiling, near chimney, with fire all year.
  4. One of each nailed to living room.
  5. One of each between several quires of paper, in close drawer without air.

Left them all for 27 months, then tempered remaining tints with water and nut oil, and prepared fresh cloths with the colours.”

His detailed tests on the canvases led him to several conclusions.

“Encaustic colours, having resisted the injuries of the weather better than oil for 27 months, they will be more lasting for longer times…”

“Having resisted corrosives, alkali, aqua fortis etc. the circumbient air, however impregnated with saline particles, cannot affect them…. If pictures of this kind are damaged, fire will restore them.”

He then carried out an investigation on oil colours painted on waxed grounds and biterely came to the conclusion that “ground is more the cause of the colours changing than the colours themselves, perhaps owing to the desiccated saline particles of the oil, which are dissolved and mix with the new oil and colours; or to the super abundant quality of salts contained in the ground or priming, which is generally composed of the coarsest oil and colours, frequently half chalk.”

By 1796, much finesse had been brought to this method, and combinations of the use of solid beeswax or beeswax mixed with turpentine were used in the preparation of not only encaustic painting but special kinds of crayon drawings. Here is the wax impregnation method as described in the Hand-maid of the Arts, published in London in 1796. “The picture deemed finished and the colours dry, prepare a clear coal fire, and set the picture with the painted side towards it, at about 2’ distance from the fire. Let it grow warm, and then by degrees bring it closer to the fire, till it be 1’ distant, but never advance it nearer. The picture may be held perpenticularly, or a little inclined, as may be found most convenient, and when it is too large to receive the effect of the heat at once, first one part and then the other, may be brought parallel to the fire at the distance prescribed. When no further change seems to be made in the picture, but the whole surface is shining and the colours rendered darker and fuller in an equal degree, it may be concluded that the wax be sufficiently melted, and duly absorbed by the colours, the picture must then be removed from the fire in the same gradual manner it is made to approach it, and kept from any rude touch until the wax be entirely set and grown hard.”

“If there be found any defective parts where the wax has not undergone the due degree of heat required in melt it, such parts must be perfected by bringing a red hot poker, or any other such metallic body near them. And if there still appear any spots where, after duly melting the wax to commix it with the colours, a deficiency must be supplied by rubbing the proper quantity on the back and melting it by any means of a hot poker or other proper implement of metal in the manner.” The whole technique sounds so modern in principle, that apart from the crude methods of heating, it is hard to realise that this method of impregnation was carried out of 200 years ago. We still face the same problems of even impregnation and the treatment of small areas which are starved of wax.

Muntz later pursued the possibility of using wax in conjunction with the normal oil technique, and carried out experiments with oil paint on wax impregnated canvas, the wax layer serving both as a moisture barrier and as a material which would stop the rapid absorption of the oil paint. It may have been these techniques that led the American painter, Charles Wilson Peale, 1741-1827 to experiment in wax impregnation. Dr. Wolters reported in 1960 that one of Charles Wilson Peales pictures, painted in 1780, was still in very good condition. Muntz came to clearly recognise the value of wax as the consolidating material. He recognised it as a protective layer which would provide a moisture barrier. He also explored the possibility of wax impregnated canvas as being an attractive material to paint on with conventional oil paints. But at no point did he propose that wax should be used as an impregnating material for existing paintings in distemper or in oil paint and, recognising the greatest danger that attends the wax impregnation principle, (that is the change of tone of the colour on infusion where that of the original paint may be drastically altered), he designed a colour regulator which would allow the artist to anticipate the colour change and darkening of paint layers when the painting had been finally impregnated.

The wax impregnation method is very common in countries of the Western world. Thousands of paintings have been lined or impregnated by the use of wax or wax resin mixtures. Not all of the paintings treated have fared well. In some cases, the tonal drop has almost a blackening effect, where the ground or the priming has been of such a colour to become considerably darker and thus the colour values of the original painting are sometimes savagely altered.

The danger of a change in tone of the paint caused by the infusion of wax or wax resin has only recently been redefined. The rough rule of thumb criteria that oil paintings will take a wax-resin impregnation, while tempera or gauche paintings will not, no longer wholly serves, for some oil paintings are almost as radically changed as tempera paintings by the wax impregnation method. References to the composition of Vasari type of ground for oil paintings or the lack of opacity of many of the fillers found in traditional and modified gesso layers such as those used by the Venetian school, and continued in various forms up to the 20th century, should cause us to hesitate before deciding on using a wax impregnation method in every case. We have also seen that many of the so called “oil grounds” are (if of the type recommended by De Mayerne) of a non-homogeneous structure and these grounds too, can easily be affected by penetration of the open cavities inherent in the structure of the material..

However, the use of gypsum, chalk and fillers was not confined to the ground and priming layers, but was often a regular component in the white paint layers of the picture, forming, with the lead carbonate, a light semi opaque paint with increased colour staining power.

The adulteration of white lead with chalk was also common during the 17th century as it is today and chalk continues to be a regular ingredient in the artists’ paints. Impregnation with wax or wax resin can alter the vehicular balance of paint layers, and lower the relative refraction index in such a way as to bring perceptiple changes of tone and quality to the paint layer. Sadly, this principle that was so clear to Muntz was not recognised by future restorers in the 19th and early 20th centuries. The tragedy of the darkening of the Mantegna Cartoons at Hampton Court can hardly be overlooked in the history of conservation. In 1931, these paintings, executed in a form of tempera on gesso canvas were suffused by heavy layers of yellow wax, irreparably bringing a darkening and lowering of their colour values and paint qualities. The advocates of the wax impregnation,(Arthur Church, Noel Heaton, Dr. Tritram, Kennedy North) are only a few amongst the many restorers who used wax in an unquestioning way. The success of wax as a consolidator for friable and flaking wall paintings led to its application in many of the finest wall paintings in English churches, often causing irreparable darkening. The frescoes by Daniel Maclise in the Royal Gallery of the House of Lords were also plunged into darkness by the rash impregnation of beeswax, heated into the surface with blow-lamps. Attempts were even made to impregnate the great Raphael Cartoons in the Victoria and Albert Museum, London, painted in tempera on paper. The rapid darkening of the painting, where the paper turned dark brown, was only checked by the sharp intervention by a youthful restorer who protested that this method was not to be used. This darkened patch remains today; it serves as a useful lesson to all restorers that the choice of adhesive must be matched to the physical and chemical structure of the painting.

When in 1930 an international conference was held on the conservation of paintings under the aegis of the International Museums Office, these aspects of wax impregnation and lining methods were discussed. The papers arising from this conference were published in 1940. The distinguished editorial committee (including W.G.Constable, the late director of the Courtauld Institute, Harold Plenderleith, Helmut Ruhermann, Martin de Wild, George Stout, A.P. Laurie, Jacques Maroger, amongst others) dealing with the possible advantages of glue and the disadvantages of wax, wrote, “Another advantage of a glue adhesive is that it interferes but very little with the optical properties of most paintings (reflecting power). Wax, on the other hand, would slightly reduce the reflecting power of a more or less absorbent white priming, and thus darken somewhat a transparent painting executed on such a ground.”

In the case of an oil painting, the wax which penetrates the paint layer or which even spreads over its surface through the crackle would reduce the depth (transparency) of the colours alittle, and thus make the darker tones appear a shade lighter and duller. In an old-master – Rembrandt or a Titian, for example – the loss of transparency would alter the effect originally intended by the artist. Moreover, as mentioned above, a varnish applied to a painting in such a condition would not retain its transparency and would tend to crackle. A remedy, however, was recommended, and this followed closely. “These drawbacks can, however, can be met by adding a little resin, as a hardening ingredient, to the wax. Rosin (colophony) is generally used for this purpose and has so far proved very successful. In inferior grades, it has the disadvantage of being rather dark, so that, for bright paintings, or for pictures where the white priming plays an important part, none but the clearest quality should be used. “This, of course was no remedy to the problem which had been outlined, of the effect of oil paint darkening by the impregnation of wax, and this misleading non-sequiteur disguised one of the greatest problems using the wax resin method.

The conference was also to bring into being the specification of an ideal heated working table for lining. The hot table described was a thick slab of slate, kept at a suitable temperature (about 50-60 C) by an adjustable electrical heating device underneath. This made it possible to ensure a uniform melting through of the adhesive to the surface of the paint, thus dispensing with the ironing of the front (on the felt bedding), which was often necessary to obtain thorough adhesion. The use of hot tables of this type was to find a permanent place in the restoration studios and workshops, and we are grateful to the Courtauld Institute for allowing us to exhibit the first hot table built in 1948 in the exhibition of lining materials connected with this conference. Although the wax resin method had been introduced first in Holland in the middle of the 19th century (the Dutch Method), the acceptance of the technique using a hot table gave the final seal of approval to the method, and few restoration studios are today without a hot table of some kind. These vary considerably in design and in size.