CaSo4

Plaster results from the calcination of gypsum (CaSO4, 2 H2O), which partially dehydrates to produce a hemi-hydrate (CaSO4 , ½ H2O). The oldest traces of plaster renders are 9,000 years old, and were found in Anatolia and Syria. We also know that 5,000 years ago, the Egyptians burnt gypsum in open-air fires, then crushed it into powder, and finally mixed this powder with water to make jointing material for the blocks of their monuments, such as the magnificent Cheops Pyramid for example. The ancient Egyptians used models of plaster taken directly from the human body. The Greeks also used gypsum, in particular as window for their temples when it was of a transparent quality ("selenite gypsum"). The writer Theophraste (372-287 BC) described quite precisely the fabrication of plaster as it was done at that time in Syria and Phenicia. The Romans cast in plaster many thousands of copies of Greek statues. Plaster of Paris. Throughout the centuries, expertise was gained in many parts of the World with gypsum calcinations. In the 1700's, Paris was already the "capital of plaster" ("Plaster of Paris") since all the walls of wooden houses were covered with plaster, as a protection against fire. The King of France had enforced this rule after the big London fire literally destroyed this city in 1666. Large gypsum deposits near Paris have long been mined to manufacture… "Plaster of Paris". From Gypsum to Plaster of Paris. Gypsum is a sedimentary rock, which settled through the evaporation of sea water trapped in lagoons. According to the nature of its impurities, gypsum can show various colors, ranging from white to brown, yellow, gray and pink. Gypsum selection and preparation (cleaning, classifying) are key factors to produce the best plasters. The chemical reaction is : (CaSO4, 2 H2O) + heat = (CaSO4, ½ H2O) + 1.5 H2O Several processes are available to calcinate gypsum into Plaster of Paris. We can distinguish two categories : 1st: Calcination under atmospheric pressure to produce Beta plaster ; 2nd: Calcination under elevated pressure to produce Alpha plaster. Controlling some critical calcination parameters is essential to master the growth of the plaster crystals. And the performance of the plaster depends a lot on its crystals' sizes and shapes. Plaster of Paris is a calcium sulfate hemi-hydrate : (CaSO4, ½ H2O) derived from gypsum, a calcium sulfate dihydrate (CaSO4 , 2 H2O), by firing this mineral at relatively low temperature and then reducing it to powder. Calcination of the gypsum at higher temperatures produces different types of anhydrites (CaSO4), as shown on the table below HISTORICAL USE OF GYPSUM PLASTER Gypsum plaster is not a modern invention like Portland Cement, as some people might suggest. We know that it was used by the ancient Egyptians to plaster the pyramid at Cheops. In Britain, research being carried out by Claire Gapper, a PhD student at the Courtauld Institute, indicates that considerable quantities of Plaster of Paris were being imported from France during Henry VIII's reign for work on royal properties. Our knowledge of the use of gypsum plaster prior to the 19th Century is limited. However Claire Gapper's research shows that it was being used in the 16th Century with lime in floors, walls and ceilings, but decorative plasterwork, which was previously assumed to contain gypsum, is proving to contain only minute traces; the sort of levels at which one would find it as an impurity in limestone. This contrasts with the use of gypsum over the last 200 years, when it was predominantly used for casting decorative elements and for gauging lime when running moldings, whilst most flat work has been executed using plain lime plasters. Although further investigation is required, it would appear that gypsum was being used in these early gypsum/lime plasters very differently from the way we expected and there is no evidence, at the moment, that it was also used for moldings or decorative work.

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 10 mg/m3 TWA; The value is for particulate matter containing no asbestos and <1% class="blueBoldEleven" name="health">Health Factors Potential symptoms: Irritation of eyes, skin, mucous membranes, respiratory system; cough, nosebleed; INGES. ACUTE: GI blockage if material hardens Health Effects: Nuisance particulate (HE19) Affected organs: Eyes, skin, respiratory system Notes: Although a study by NIOSH of causes of death among plasterers found a significant increase (24%) above the expected incidence for lung cancer, this increase was attributed to the asbestos component (5-12% by weight), rather than the plaster of Paris component, of most spackling compounds that were in use up to the late 1960s. Date Last Revised: 10/04/2005


Remember that plaster of paris is in some way re usable if you put it into an oven or kiln and expel the water content at high temperature, it is not so hard subsequent times but can be used in certain cases.

How to do it

This is my current job and it was started just before my eye accident, detached retina, I had done very little before the accident so I am pleased that at least I can work, although I am having problems with seeing some detail but it is a far cry from six weeks ago, I was given a prognosis that I may lose the sight, or certainly a part of the sight.
I think there are so many books available on the basics of cabinet making and for the furniture restorer, that I will keep most of my blog for notes that can help or go a bit out of the general pattern of tutorials. Still here is a mix of books and some fine tools, just a small introduction.

seeing colours

There are many different attitudes and techniques to the restoring of paintings, many opinions as to how to restore without adding to a painting or giving an impression of union that may falsify the state of the painting on arrival, before restoration, the other term is of course, conservation, this rather indicates a less intrusive state of repair. The problems of mixing colours and assessing what is missing in areas can lead to arguments as to the restorers taking too many liberties with a painting, possibly worse when the skilled restorer can leave very little evidence of his/her work. One opinion to overcome this is the use of colour harmonising, the human eye as a natural tendency to fill in gaps and compensate for missing colours, in an extreme example it will provide colours if it is deprived.
Here is an abbreviated version from a book published around 1836, in Edinburgh for sale in the same city, it is to provide guidance to interior decorators and painters. The colour wheel is the starting point but it is later that we get an idea of how the modern restorer can use the eye of the viewer to paint the missing parts.
Colour harmony-
there are three distinct primary colours, yellow, red and blue as there are three distinct notes in music, C, E and G, and seven distinct colours as there are seven notes for a complete scale.
If the colours are given numbers to show their values we will see that yellow = 3. Red = 5. Blue = 8 and when these colours are mixed together in these proportions, on an opaque body, the result is white, or white light, for the eye needs to compensate for each colour viewed with its opposite colour in the spectrum, giving rise to the colours being dismissed, appearing white. It is largely a reflective phenomenon that takes its results within the brain and not at the point of the colours mixing, similar to the way the brain can be made to cancel out sound with hearing other sound.
Secondary colours are then the mixture of the primary colours and therefore have joint values -
Orange has the value of 8. it is red(5) plus yellow(3).
Purple has the value of 13. it is red(5) plus blue(8).
Green has the value of 11. it is yellow(3) plus blue(8)
These colours are called accidental or contrasting colours and if they are then mixed with a primary they get a value of 16.
Orange(8) with blue(8) = 16. Purple(13) with yellow(3) = 16. Green(11) with red(5) = 16.
Tertiaries or thirds are a further mixing of the colours and are called neutral hues, if given a value of 32 they are termed neutral, having a neutralizing value, the most neutral being grey, black plus white.
Olive(24) comes from mixing purple(13) with green(11).
Citron(19) comes from mixing green(11) with orange(8).
Russet(19 comes from mixing orange(8) with purple(11).
The tertiaries give rise to other colours, such as brown, marron, slate - gradually arriving at their neutrality with the forming of black. One primary a harmony with two others, yellow will sit withorange on one side and green on the other, blue with the green and purple, the red with purple and orange.

Hue is a compound colour that is undiluted, primary colours cannot be hues because they change their name if another colour is added to them.
Tint is a gradation of colour in lightness, from the intense to white.
Shade is the gradation of colour or hue, in depth, from perfect to black.
To contrast, colours must bear relation to each otherin the power and point of tint, hue and shade, a tint of one colour,brought to an arrangement of contrast with another, must be equal in its diluteness, the same holding for colours receeding from their origional purity towards black; they are less powerful according to the dilution or shade.
Complementary colours - in pairs, yellow with violet, blue with orange, red with green, each pairing having the colours of red, blue or yellow in them, each pairing when mixed forming grey; so yellow plus violet gives grey, orange plus blue gives grey and red plus green gives grey.

AFTERIMAGES AND SUCCESSIVE CONTRAST

Figure 3.5. Afterimages and successive contrast. Stare fixedly at the centre of circle A for at least 20 seconds, then immediately look at the centre of circle B for about ten seconds, noting the changing afterimage. Each sector will display an afterimage the colour of the additive complement of the stimulus colour. Repeat the procedure, this time looking immediately at the centre of circle C. Now the colours of the afterimage in each sector will influence the appearance of the red colour in an example of successive contrast.A psycho-physical reality with the eye can be observed when viewing a colour, for instance green, for a period of time and then closing your eyes, on re opening them at a different image, it super imposes a red image and not the green that it had seen before, it is a phenomenon called contrast of succession, the eye presented with a colour demands its complementary and if denied, it will create the colour that it feels is missing. If one places within a pure colour, a grey square of exactly the same brightness, then this grey on a green background will become a grey with a red tinge, on red it will be grey shading to green, on violet it will be grey with some yellow and on yellow, it will be grey with a hint of lavender - 'the reality of a colour is not always the same as it's effect'.

It is possible to infill colour on a painting using this theory, the method can now be achieved with the use of cameras with colour filters and the use of computers to calculate the exact colour to fool the eye by combination of measure and intensity, it allows the restorer to apply colours, which on close inspection are not trying to copy the original, which the viewer will form an interpretation, thus avoiding any imitation of technique or falsifying the image.

Several dramatic optical illusions demonstrate colour constancy in action. In the checkerboard illusion by Edward Adelson's (Figure 3.6A), the two squares marked A and B are actually identical in lightness on the image, but our visual system calculates that in a shadow area this grey must belong to a white surface, while in the lit area the same grey must belong to a dark surface, and that is how we see them. In the same way, in the cube illusion by R. Beau Lotto (Figure 3.6B), our visual system sees the same image colour as being dark brown in the context of strong lighting, and light orange where the same image colour appears in a deeply shaded context. In the cross-piece illusion , also by Lotto (Figure 3.6C), the colour at the intersection of the two rods is actually an identical colour (grey) in both cases, but in the context of apparently yellow illumination on the left and blue illumination on the right, this is judged, and seen, to be the reflectance of a blue-grey object and a yellow object respectively.

Figure 3.6. Three o

the feel of history

It is important to have a reasonable grasp of the basic history of furniture when repairing and restoring, as with any art works, to know the development of furniture allows you to look for tell tale signs od deterioration, some times stopping further problems from occurring.
Age can been approximated by various details in design and construction, a knowledge of this will give rise to a more sympathetic restoration and one that can be quicker and easier to perform. If you are aware of the date for different forms of casting materials it will follow that you can have an idea of the age of a cannon or brass telescope, also it will be apparent in the style of an oak chest, done without any glue being used, the approximate age, the cutting of veneers is another example, the reduction and scarcity of exotic woods started to create a market for veneers and the finer the veneer the more could be extracted from the rare source material. The development of the nail and screw, from blacksmith wrought to engineers turnings gave signs for one to assess the age of furniture, this is why a restorer keeps all the old nails and screws that he/she comes across, it is even more necessary now since the availability of the common screw is itself threatened by the philips or posi drive.

A normal way to judge any antique is to pick it up and feel its presence, touching an object can gives instant indication of its material, texture, density and weight, with wood, the colder it may feel can give the impression of more density, heaviness, with visual appearance this can be a sign of more mature timber and more age, the passing of your fingers over the surface will give an idea of the grain's texture, type of wood and its age may again be established when added to the visual inspection, finer grain may be true of a longer growing period and older variety of a species of timber. The fingers will also pick up tell tale signs of previous repairs and changes in polish or laquers.
Knowledge of different timbers can be useful in assessing types of glue that are practical and how certain polishes will take to the surface, it may be necessary to de grease timber or roughen it in order for glue to hold. Antique mahogany very often had virtually one coat of polish or just oil, as a means of enhancing the grain, whilst the Victorian period needed to apply possibly seven or more coats on top of flling the grain with plaster of Paris, the later timber was so open that it needed to be filled and still it would absorb huge amounts of the shellac polish.
It is often the case that your only contact with the origional makers or artists, is with their work, this can, if you wish, have an intimacy , for you will see far more of their marking out, mistakes and style of construction or painting that is solely their own, often you will see the small marks of a chisel or marking gauge, the difference of one maker to another with the shape of a curve, which can also be indicative of age, as is evident in the changing styles that can be seen in front legs of a chair and table legs.

The concept of patina and its association with age is worth remembering when re polishing furniture or cleaning paintings, it is not necessarily good to remove all signs of age but it may well be worth clearing the cloudiness of a shellac polish for the true colour and grain to be appreciated. The refractoriness of a shellac polish, alters with age and when the light can no longer pass through the once transparent layer, it is reflected as a white or bleached look. Some times we may well be valuing the age of an object and not its aesthetics, early veneered pieces where often made to be, by our tastes now, very bright and gaudy but time as tamed them behind a cloudy varnish, we are used to them as pale objects, yet if they are cleaned and the polish is revitalised, there can appear an all too different beast, this has been the start of many arguments in the field of restoration with paintings, for many centuries the restorer was aware of the likely controversy, cleaning would have, so they would clean and then re varnish with a tinted varnish so to not offend the viewer.
The appreciation of art is not always clear and it is shown in a short note about Shelley, whilst touring in Italy. 'travelling in Italy, he arrived at a convent just as the village plumber, glazier and painter(house), was withdrawing his workmen from their task of touching up the old masters,which operation had been included in the contract for renovating the paint and whitewash of the Holy edifice'
A note about fillers, gesso is historically used as a base for paintings, like most things with paintings, the process often then gets passed to furniture, the lifting, relining and transferring of paintings was done far earlier than the use of veneers on furniture but the veneer is glued with the same process as the early artist/ restorer used to remount the ageing canvas. Gesso with animal glue is the base for paintings and often used as a base for furniture that requires a high lacquer finish, plaster of Paris, if mixed and spread over the timber will, once thoroughly dry, take polish on top of it and become transparent as it absorbs the shellac, or can be stained with the whole of the piece before polishing, I often seal timber with a thin coating of animal glue before staining ,so as to limit the stains effect on the changing direction of grain, going darker into the end grain and staying pale on the side of the fibres, this is another point when staining, to slightly roughen the grain in order to get a more even colour. A gesso paste can be made from- white lead, some ochre, oil varnish(siccatif de courfrais) resin and turpentine oil, after drying the gesso must be sanded and when dry, coated with a 10% size solution( animal glue that is diluted so that it is more of the consistency of yoghurt) to prepare the gesso, a small quantity of the glue size is placed o a roughened thick glass palette, alabaster plaster is then added until, after working with a palette knife, it forms a firm, barely malleable paste, care being taken not to arrive at a gesso that does not correspond to the area to be repaired, not to be darker than its surrounding, for light areas white pigment is added and for darker areas, more ochre. Finally some amber varnish is added in small quantities, constantly mixing to form an easily malleable paste. A horn palette knife or spatula is used to firmly and precisely spread the paste into the defective areas, completing the process with a little water to smooth out the final surface, on paintings it will be necessary to wipe the surface with a moist cloth so as to leave the gesso only in the areas of damage and not on any of the paint. This gesso will hardly shrink, should remain firm but porous, its absorbency making it ready to accept further treatment, it is possibly best to let the gesso sit very slightly below the true level so as to allow varnish and paint to be applied up to the true level.


An assistant some years ago remarked, on seeing me use saliva as a vehicle whilst restoring a piece of furniture, that it was highly unprofessional, and when I asked why, he said that most of what he saw me do was not to be found in any of the books that he had read or at the college that he had been . I remarked to him that there can be certain limits to the amount of knowledge he may find in books and that it is always a case of learning first and discarding afterwards, he was welcome to use or discard what ever he saw me do but as my knowledge spanned more than thirty years it was worth considering why I did what I did. Linseed oil, resin, mastic varnish, copal, lavender oil, lye, butter, common wood ash and even soil, where used in the cleaning of paintings, to brighten the paintings, certainly it is not advisable to copy all these but it is worth considering why they might work and where you can use them safely. Spit is a very good cleaner and will dissolve grease and dirt a lot quicker than many propriety cleaners, a lot safer as well, the artist often used egg white as the only means of getting an even glaze to a new painting before it had time for the paint itself to harden, which could be several months to a year, using a varnish too early on would coarse the paint to remain liquid beneath a sealed coating where as the egg would prevent dust and smoke sticking to the fresh oil paint and still allow the oils to dry naturally.
Varnish-middle English vernisshe, from Old French vernis, from Medieval Latin veronix, vernix, sandarac resin, from Medieval Greek verenikē, from Greek Berenikē, Berenice (Benghazi), an ancient city of Cyrenaica.]
Copal, is a slow drying resin, several species of the genus Copaifera, the trees of the Leguminosae family, growing in the tropical regions of the Americas. Deep incisions, canals( similar to those made for extracting latex) are cut into the bark and the balsam flows as does the turpentine of the pine tree, another natural oil ( not to be misconstrued with the white spirit that is sold as a cleaner)
Copal is made up of solid resins and etheral oils, this is similar to resin varnishes, which are a solution of mastic, or Damar resin(resin from India) in oil of turpentine. Genuine copal has a consistency of fatty oil but does not contain oil for the purpose of painting or conservation. When heated in a porcelain bowl, it should not give off any odour of turpentine, and on cooling should be a transparent, brittle resin.
Copal for balsam( para balsam) and the more viscous (maracaibo balsam) differing in the content of etheral oil, the para balsam will change to the maracaibo if left to stand in contact with the air for a long time, or by boiling with water. Copal as low tension properties, and slow drying, turpentine oil is on the other hand has a tendency to evaporate quickly at low temperatures and will have higher tension; copal, heated in a retort over water,will stay virtually unchanged after cooling,while, under the same conditions, conventional resins and that of turpentine will solidify. Contrary to this, linseed and poppy oils are used in the making of oil paint because of their tendency to dry quickly.

Integrity of the Restorer

It may be that before 1800 the painter was an artisan first and his studio a workshop with apprentices and craftsman alike working together in their expectation of producing work that would last many centuries, they produced their own colours, made their own grounds and passed on their knowledge to their students, all with the aim of continuing a tradition for employment, the only possible reservation was to have kept this within the confines of the town or city. Later artists had developed a more insular approach and with it have come the development of the brush, paint, varnish maker, framer and guilder, all separate entireties and all possibly subject to other market forces that may create the need for economy of materials or the vagaries of a market force with supply and demand adjusting price. This off the shelf approach would certainly have led to the artist being separated from intimate knowledge of his materials, especially the quality and content of the materials, also the painter gradually became less concerned with the quality or the longevity of his/her work, not appreciating the re sale but only the initial sale value, leaving others to find that they had bought a painting that now required maintenance, a very good example of this was the painter William Turner, whose almost cavalier attitude to paint and its application, led to his works cracking and flaking within months of their completion, thankfully his drawings and water colours where free from these problems. The earlier painter, by over three hundred years, Van Eyck whilst developing and learning the process of painting in oils, produced such quality paintings that they are now among the most well preserved of all art, sadly the expertise that he and his brother developed went to the apprentices but does not seem to have travelled beyond and saved the rest of art from the vagaries of bad technique and poor quality paints.

It is difficult to think how works of art before 1700, largely religious subjects and commissions, would have survived without them undergoing restoration, retouching or repainting, the continuance of style change and the gradual change of emphasis within the church, will have led to many paintings being up dated, given altered prominence and fresh adornment, provided by eager young artists that would need new commissions and seek fame. This would be for the church and the artists an ongoing work of art, almost seen as unfinished and certainly not the ownership of the original artist, the extreme of this can be seen in the ‘Guilio 11’ statue, by Michelangelo, becoming the ‘ Guilio Canon’.

The sensitivity of the eye and the ear has become something of a daily demonstration to me, with an almost loss of sight in the right eye, which is progressing well at the moment, and the diminished sight in the left eye, no longer able to improve the state of this eye, I have become aware that my hearing has adapted quickly , becoming more responsive and giving me more special awareness that seemed before to be the priority of my eyes.

My experiences whilst working for the theatre as a free lance scene painter, taught me to use daylight when ever possible and to use lamps that had a daylight factor when needed, for to get the colours correct and the tonal values balanced it was bar far best in natural daylight. This was however studio practice and when the canvas was sent to the theatre it became necessary to rework, under artificial lights, the canvas because of the demands from the designer, director and lighting director, the colour balance would be completely altered by the intensity of light and the use of coloured filters, a similar result is found when paintings are hung in galleries that have artificial lighting and coloured walls or floors. The direction of the light and its subsequent reflected angle can transform colours and hues, for it needs to be remembered that ‘ a painting as few tactile attributes. It is totally dependent on surface reflectance’

The play over light over smooth or impasto surfaces alter the effect that the eye perceives and that the relining of a canvas as well as the cleaning of the same can alter the viewers appreciation of the artists intent- ‘ the conservator’s primary loyalty is to the artist’ and then the artist can influence humanity.

‘Solvent action and the degree of persistence used in the removal of oxidized layers have a profound effect on the visual values’, ‘white, for instance, is not simply a tone but a colour’ and is worth noting when we consider the painter as an individual, all painters as individuals along with the spectators and restorers, not all painters, spectators and restorers view colours with the same sense of value. The surgeon, as it where, needs to remember that the work in front of him/her is an individual work of art with their own need to expression.

The gallery as well, as the restorer, needs to consider how best to show works of art, it is important for students to see the real article and not be content with a photographic record. Travelling to school, generally took three buses each way, meant that the return would take me through the city centre of Birmingham on foot and gave me the opportunity to spend time in the city art gallery before it closed in the evening, good during the summer or on wet evenings, this offered me the chance to see painters work on a regular basis and my joy was to look at the large collection of Pre Raphaelite paintings, their intensity of colour and craftsmanship was a constant inspiration to me, it could never be the same to have seen these fine works as photographic copies, especially when you may consider that those who produce the copies have never seen the originals. This is the danger therefore when applying varnish, especially the liberally applied tinted varnish of the past, in the cleaning or restoring of a painting, the fine glaze of pigment that may have been used by the artist to change the colour or hue can be lost or altered beneath a varnish or removed by a careless worker whilst cleaning, lost or removed with such ease, sometimes without the restorer noticing, can alter the artists intention or vision.

From a restorers view point there are many aspects of aging that cannot be redeemed or altered to good effect, pigments oxidize and change colour and effect the surrounding pigment, the effect can alter the balance and depth of a picture, a fading yellow that had been mixed to form green, will now leave an area blue.

Now a final comment in this posting on my blog, the use of oil as a medium was clearly known in antiquity, mixed with pigment and used as a paint, mostly to give extended time on frescoes, the paint applied as a dry, coat, secco, used sparingly, later this was used with tempera in the same manner but the whole would be varnished in order to preserve and give the dry looking tempera a more brilliant and deep colour. This coating could also be retouched and re-varnished, a procedure that would gone on for centuries. Clearly it should not have been any great step to try and make the medium and the preservative as one coat, to dismiss the egg yolk as a base and use only the oil and varnish. There is a problem however in the chemical make up of the pigments used, they are not all equal and have structures that are very different, ranging from metals, stone and vegetable bases, chemically not stable and often light sensitive, extended periods of time and sun light are able to change and fade the colours, this and the lack of consistent development as given rise to the restorer becoming so much more of an academic, if not now a scientific post but the essential that we must remember is to pay homage to the artist, when we attempt to restore a painting and not indulge in a re interpretation.

The use of animal glue as a medium is also one that I am aware of through my time in theatre, when I first started work in London we restored sets that had been painted during the 1930s and they were painted with glue size and pigment, most of the time we used whiting as a bulk pigment and then added other colours, unlike Titanium white, whiting had very little covering power but bulked the medium. The advantages for glue size was that at the end of the play's run the canvas was laid face down and the back of the canvas was drentched with hot water and scrubbed, resulting in the whole image lifting from the canvas and leaving it fresh for a new image to be painted. Animal glue can also be used with gesso, traditional priming for most early paintings and especially for early oil painting on wooden panels, the panel would be spread with a mixture of glue and gesso, using a spatula to smooth the surface, on drying it was then pumiced down and coated with more size, this led later to the same method being used to create a copy of 'Japanese lacquer', the animal if left to boil for some time becomes very hard and brittle, can be worked over almost the same as bone and then varnished and coloured to appear as tortouse shell or Japanese decoration.

Lathes

The candle stick above is a piece I made for a client in Glasgow.
The pole and bow lathe have certainly had a long history and have not been solely used for wood turning but also for ceramic and metal work.
Today I have been on the lathe turning bone collars for an old velum portable telescope, the bone is irregular and needed to be softened first, hot water, then placed on a former, a tapered bottle, allowed to cool to hold the more rounded shape and the held on the lathe with some adjustable chucks whilst I firstly cut the inside diameter correct for the tubes and then formed the outside shape to form a collar with a small ring, so as to be able to catch each tube seperately with the fingers and extend the telescope, similar to those used at sea. Then the art is to sand it to a more irregular shape and tint the bone to appear old, in keeping with the velum tubes. One other job today is the repair of the base for an old Rose lathe that once worked its pay in the centre of Birmingham's jewellery quarter






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Origins of the Lathe
Since we are dealing here with a specialized form of lathe turning,
it would be well to give some of the history of the lathe itself. The
name, which is a linguistic curiosity, comes from the English lath
which was a pole or split strip of wood, and was used as a spring
power source for early lathes. In India, for example, a lathe was
called a chakra, a wheel, and it is common to other languages than
English that the term for lathe has a relationship to a wheel, or
circle. The lathe is a tool of rotation and the works generated
thereon are always 'solids of rotation'. That is to say that if a
cross-section be taken perpendicular to the axis of rotation, this
section will always be a true circle.





Turning is the process of shaping an object mounted in a lathe into a
rounded form by applying tools against the workpiece as it spins.
Plain turning creates objects whose every section is a perfect
circle. Ornamental turning, however, works upon the plain-turned
shape to apply some form of ornament by means of an externally
powered cutting device. The cut surface which results can evidence
great complexity of decoration. A variety of types of motion and
interaction of workpiece with cutter is possible. The workpiece may
be held stationary by an indexing device while an external cutting
tool is brought in to make a cut; when indexed and the cuts repeated,
this can create a basketwork effect of pattern among many others.
Additionally, the work and cutter may move in a synchronized motion
maintained by means of gear trains much as in the cutting of screw
threads on a machinist's lathe. A rocking motion is also a possible
complication of technique when using a specialized ornamental lathe
called a rose engine. The embellishment of plain-turned objects with
designs can elevate merely utilitarian objects into the realm of the
decorative arts.


The lathe, termed "the engine of civilization," unique amongst
machine tools in that it is the only machine capable of replicating
itself, is also capable of manufacturing all other machine tools. Its
history dates back at least 3000 years. There are extant fragments of
an Etruscan bowl dating to 700 BC. An illustration of a lathe carved
on an Egyptian tomb wall dates to 300 BC. The Egyptians undoubtedly
turned the legs of chairs and stools and other long objects. Though
they did not leave us with descriptions of their lathes, the
Egyptians did describe and picture their potters' wheels and bow
drills, both forms of vertical lathes.
The lathe was certainly known in Grecian and Roman times, though no
accounts remain of it or the tools employed in turning. Cicero and
Pliny refer to the turners or vascularii, and the master Greek
sculptor Phidias is assumed to have turned cups before encrusting
them with ivory and then carving them with chisel and file. Herodotus
is quoting as saying, "But I smile when I see many persons describing
the circumference of the earth, who have no sound reason to guide
them; they describe the ocean flowing round the earth, which is made
circular as if by a lathe." Virgil, as translated by Dryden,
describes in the following passage a process whereby wooden bowls
were plain-turned and ornament was then hand carved upon them:

Two bowls I have well turned of beechen wood;
Both by divine Alcimedon were made;
To neither of them yet the lip is laid.
The lids are ivy: grapes in clusters lurk
Beneath the carving of this curious work.

A primitive apparatus used in India is likely illustrative of many of
these early lathes. The Indian lathe was portable, and set up by the
turner at the site where work was needed. Two wooden poles were
driven in the ground and the work mounted between them on centers
which were simply round nails or spikes driven through the mounting
poles. A bar or rod was then lashed with cords to the two poles to
serve as a toolrest. In use, the turner sat on the ground and guided
the cutting tool edge with his toes while holding the handle with his
hands. Motion was imparted to the workpiece by means of a cord
wrapped around the workpiece which was pulled by a helper. Cutting
could only be done on one-half of the motion, that of the workpiece
towards the tool. Early Persian and Arabian lathes work on a similar
principle, but are more sophisticated in that they are built into a
box and the power is supplied by a bow and string

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The Lathe Through The Middle Ages in European History
The lathe was introduced into England at least by 200BC by the Iron
Age Celts. In the West, improvements to the lathe appear to have
arisen from a different method of rotating the lathe conditioned by
the European habit of selecting the erect posture for most mechanical
operations. One end of the driving cord was fastened to a treadle or
stirrup, it was then passed around the workpiece and then the other
end was fastened overhead to a pole or spring above the lathe. Such a
technique greatly increased the power of rotation and left both hands
free for controlling the tool. The paucity of written records leaves
us little information about the lathe during medieval times, and it
is not until the Renaissance that evidence of the use of lathes
appears. Gio Paulo Lomazzo described the oval turning of Leonardo da
Vinci (1452-1519) in 1590. The following verses accompany an
illustration of a turner in the book "Panoplia Omnium," by Hartman
Schopper, published at Frankfort-on-the-Main in 1568:

A turner I:--with unremitting skill,
I turn from yellow box, whate'er you will:
Boxes of shapes unnumbered we produce
And who can tell our boxes' varied use;
There may'st thou store, secure from stranger's view,
Thy noble treasures of the brightest hue,
There too the ball is made, which--wondrous sight!
Struck by the wand, rebounds in varied flight,
Here too the top, that warms the schoolboy's force,
And whirls on level ground its well urged course.

The first book dealing specifically with ornamental turning as well
as 'plain' turning was published by L'Abbe Charles Plumier in 1701.
Joseph Moxon described turnery in his book Mechanick Exercises or the
Doctrine of Handy-Works in 1703. Denis Diderot D'Alembert prepared
the first encyclopedia from 1751 to 1772, and therein illustrates
lathes and the work done on them. The great classic of early turning,
however, is Le Manuel du Tourneur published by L. E. Bergeron in
1796. This comprehensive set of two volumes, containing 96 plates,
was published for the aristocracy rather than for the artisan. In
great detail it illustrates the state of the art at that time. By
this era, lathes had developed into very sophisticated machines from
their humble origins.


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The Invention of the Modern Lathe(ca. 1700)
The modern lathe was not actually invented, but was a product of the
refinement of input from many sources. Its evolution was one of
gradual improvement. One key element to this development was the
introduction of a large flywheel separate from the spindle that could
serve to maintain a uniform speed and always allow the lathe to
rotate in the same direction so that cutting could be continuous.
Moxon, in 1677, describes the advantages of this improvement to
powering the lathe:

Besides the commanding heavy Work about, the Wheel rids Work faster
off than the Pole can do; because the springing up of the Pole makes
an
intermission in running about of the Work; but with the Wheel the Work
runs always the same way; so that the Tool need never be off it,
unless it be to examine the Work as it is doing.

So with a flywheel to store energy and redistribute it with a uniform
motion, and a treadle and crank to allow the turner to stand and pump
power to the machine with his legs, the turner had both hands free to
manipulate tools.

Another important refinement to the lathe was the introduction of
iron bearers for the bed instead of wood. The iron would maintain its
alignment and if a carriage be mounted on a bearer of triangular
section, it would serve to keep it in a true relation to the lathe
axis for its whole length. The accurate bed then served as a platform
for the final refinement which was the moveable carriage connected to
the spindle by means of a gear train. In the 1780's, the French
inventor Jacques de Vaucanson (1709-82) built an industrial lathe
with a sliding tool carriage, advanced by a long screw. Then almost
simultaneously in 1797, Henry Maudslay (1771-1831) in England and
David Wilkinson (1771-1852) in the U.S. improved this lathe by adding
a sliding tool carriage geared to the spindle. By this means, the
carriage mounted with a cutting tool was able to move in
synchronicity with the spindle at a constant speed and the cutting of
accurate and repetitive screw threads became possible. This
breakthrough heralded the age of mass production and interchangeable
parts. With lathes this sophisticated by the end of the 18th century,
ornamental turning began to reach a state of high development.

| CONTENTS |

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The Refinement of the Ornamental Lathe
by Holtzapffel, et al.
Generally considered in the same breath with the term "ornamental
turning" is the family name of Holtzapffel. John Jacob Holtzapffel
moved from Alsace to England in about 1785 and opened his engineer's
tool business in London in 1793. His first lathe was sold to a Mr.
Crisp on June 31st 1795, the outfit costing £ 25-4s-10d. When one
considers that today this would be over £ 2000, or $3000US, and that
the skilled mechanic of the day earned less than 8d per hour, this
lathe represented over 3 months wages. All of Holtzapffel's lathes
were numbered, and not all had full ornamental turning apparatus
included. By about 1805, after the Holtzapffel firm had reached
nearly No. 500 in their numbering scheme, almost all lathes had iron
beds instead of the previously used mahogany wood beds. The last
lathe sold was Holtz. No 2557, made in 1913/14 and sold in Nov. 1928.
No other maker of ornamental lathes matched the productivity of the
Holtzapffel family in the field of ornamental lathes.

When John Jacob I died in 1835, about 1600 lathes had been sold by
his firm. Not all were fully equipped as ornamental lathes, but with
the large number that were, quite an impetus was given to ornamental
turning as a leisure occupation in England. The introduction of the
cutting frame by Holtzapffel allowed for significantly more complex
patterns to be cut as compared to what could be done previously with
only the drilling frame. The elder Holtzapffel standardized his screw
threads before 1800, his spindle thread being 9.45 threads per inch
for example, and the firm maintained this standard throughout all the
lathes they manufactured. This standardization was initiated long
before any kind of screw standards were established for industry at
large.

The son of John Jacob I, Charles, who joined the firm in 1827, began
the monumental series of five books that were called Turning and
Mechanical Manipulation in 1835. This ambitious effort, comprising
over 3000 pages and 1600-odd illustrations, was intended to be a
complete survey and overview of all the mechanical arts of the day.
It was not until 1884 that Vol. V was published by the son of Charles
Holtzapffel, John Jacob II. However, it was not until 1894, with the
addition of a revised and enlarged version of Vol. III, that the set
was complete. Today, Vol's. IV and V of this series are known as
the "Bible of Ornamental Turning" because of their wealth of
information about all aspects of the craft of ornamental turning.
Charles managed the firm until his death in 1847. He was considered a
distinguished engineer, developing and inventing various devices. An
obituary notice remarked of him that,

Mr. Holtzapffel probably never put his hand to a machine which he did
not improve, and his practice in the construction of machines has
been more miscellaneous probably than that of any other mechanist,
his workmanship more accurate, and his general mechanical
arrangements more refined...He had all the humility of genius without
its eccentricities, and his heart habitually overflowed with kindness
towarrd everyone around him.

Charles' wife, Amelia, ran the firm until 1853, and in 1867, Charles'
son, John Jacob II, became head of the firm until 1896. He died in
1897. A nephew of Charles, George William Budd, became head of the
firm in 1896. Few ornamental lathes were made after the turn of the
century and the 19th century was known as the zenith of the
ornamental turning lathe. Many lathes were sold to the aristocracy of
England. The earl of Harborough, for instance, bought nine
Holtzapffel lathes between 1812 and 1848. This was certainly not
common, but is instructive of the popularity of these machines once
one developed an affinity for OT.

The contribution of John Jacob Holtzapffel's work was significant in
several respects. As expressed by Walshaw (see Bibliography), "First,
he brought the cost of the machine down to a figure which a
mere 'gentleman' (or even a prosperous tradesman) could afford, and,
second, the design was both elegant and functional." His designs were
much improved over the lathes previously made on the continent of
Europe. Holtzapffel also was a master of marketing apparatus to his
clients over time. Improvements and additions to apparatus increased
the capability of his equipment and induced his clients to continue
to be his customers. The remarkable set of books by the family were,
in effect, an extensive set of owner's manuals for their machines.




In addition to the Holtzapffels, other makers produced ornamental
lathes. Among them were the ornamental lathes of John Evans (1843-
1919) which were of high quality and counted some improvements over
the Holtzapffel lathes to their advantage. A large number of lathes
were attributed to his firm, and improved overhead drives, sliderests
and cutting frames marked the work of this talented machinist. He
also wrote a book on ornamental turning which some find much more
easily understandable than the Holtzapffel books. George Birch and
Company made a few ornamental lathes, but they were essentially
engineers' metalworking tools which were given the necessary
components to do ornamental turning. George Goyen, a retired South
American railway engineer who took to making lathes as a hobby, is
generally credited with singlehandedly creating the finest ornamental
lathes ever produced. He probably made his lathes for his friends'
amateur use and only ten Goyen lathes are known to exist. There were
other makers such as George Plant, George Hines, Hulot, James Munro,
Joseph Fenn and James Lukin and many of them made lathes of a caliber
of workmanship equal to a Holtzapffel. Lukin also wrote a book (see
Bibliography) on ornamental turning and Frank Knox considered
it "second only to Holtzapffel in usefulness," as "Lukin clarifies
much of what Holtzapffel leaves unclear." There were indeed other
toolmakers who made ornamental lathes, but these makers are those who
have left us with extant examples of their machines.


A typical example of an array of ornamental cutters is seen in Evans'
book. This was an assortment of cutters that would be in a basic
collection from any of the ornamental lathe makers. Cutters such as
these were mounted in the universal cutting frame, the horizontal
cutting frame or the vertical cutting frame and could produce a great
variety of pattern, especially if the cuts from several cutters were
combined in the design of the pattern.

Many specialized chucks and apparatus comprised a complete ornamental
turning lathe package.Typical of the presentation of apparatus for a
Holtzapffel OT lathe is this array of gears and accessories for the
spiral and reciprocator apparatus. They are housed in a finely-
crafted mahogany box, and are beautiful to look at and in use. A
drill frame was necessary to do work in which the cutter rotated as a
modern router bit would. Pearls and other features could be created
depending upon the profile of the cutter. An eccentric cutting frame
allowed for shallow circles to be cut with adjustments to vary the
diameter of the circle cut and its displacement from the central axis
of the piece. With careful thought and design, very intricate
patterns of a geometric nature could be rendered by this technique.

Other apparatus included a variety of special-purpose chucks, such as
the eccentric and rectilinear chucks. It was also possible to create
ellipses and, by means of a compensating index, create equal
divisions of the ellipse. A geometric chuck comprised of a complex
set of interacting gears would allow tracings to be made that would
demonstrate complex geometric curves, such as the epicycloidal
pattern. Much ornamental turning was done in ivory, as it produced
the finest cuts and allowed for great delicacy of pattern due to its
hardness and strength. At times, incredibly intricate work was
performed by the Holtzapffel firm to illustrate to the public the
capabilities of their machines.

A beautiful example of the finest work put out by the Holtzapffel is
in this Rose Engine Lathe, one of only 8 ever made. These were a
specialized type of ornamental lathe in which the headstock rocked
back and forth as controlled by a rubber moving against a rosette or
cam-like pattern mounted on the spindle at the same time as the lathe
spindle rotated. Rose engine work often reveals flower patterns, and
convoluted, symmetrical, multi-lobed organic patterns. It has the
potential to be very complex and to produce beautiful and unique
patterns unlike any other on the ornamental lathe.

Excellent engraved plates of ornamental turning and an extensive
depiction of various OT apparatus can be found in Holtzapffel Vol. V
(see Bibliography). Much of the historic ornamental turning machinery
that has survived is now held by collectors or is in museums. Only a
small number of machines are still being used for their intended
purpose. Most of this machinery bespeaks an era of unbounded optimism
and is beautifully made and a joy to view and use. They represent a
time in history when quality still meant "excellence." To my view,
the makers and users of this machinery were obviously on a quest to
participate in the experience of beauty and "a thing done well," and
from our own perspective in time, succeeded admirably.
Here is an extract from the site Regia Anglorum,

Timber was the most important resource for the Anglo-Saxons and Vikings. The early medieval carpenter was not only skilled in working the wood, but also in selecting the correct timber and shape for the job. If the finished item needed to have a curve in it, the carpenter would select a piece of timber that had the correct natural curve. You can use natural junctions where a branch joins to the tree as joints that have grown to suit a job that you had in mind. These natural joints are stronger than man-made ones and save the carpenter a lot of time creating joints. Wherever possible they would 'follow the grain' to leave the finished product as strong as possible.

To a certain extent, all the peoples who lived then managed their woodlands, although if a tree needed to come down for a building let's say, as far as we know they didn't replant to replace that tree deliberately. A thousand years ago, trees were still a resource that would have seemed limitless. It takes for example over 80-90 years for an Oak tree to become large enough to be useful. Large scale timber production had yet to make the impact it would later. A large stand of trees felled would just be providing clearance for yet more farmland. The Vikings are regarded to some extent today in Iceland as 'environmental terrorists', as they eventually felled all of the trees that had once grown there. The Iceland we see today has been irrevocably changed due to their habits.

A great deal of Saxon and Viking woodwork was done 'green,' that is the timber was not seasoned (dried out over time) before working. This meant that the timber could be split easily (green oak can be split with a seasoned wooden wedge), and need not be sawn. The big advantage of using cleft (meaning split) timber is that it is less likely to crack as it dries.

Most of the 'roughing out' and shaping was done with axes and adzes. The saw has obvious advantages. It can cut out a straight piece of timber every time, splitting can result in planks that are twisted etc. But the trouble with saws was that they were very expensive and difficult to maintain and make. At the time of the Domesday Book in 1086, only 13 saws were recorded in the kingdom. These were probably large saws for what is called 'ripping' down the beam of timber to create planks, as much smaller bow saws are routinely shown in manuscripts.

The trimming and shaping with Adzes and Axes is quite a wasteful process as well. With saws, large pieces of wood can be separated from the job at hand, leaving you with a reasonable piece of wood that can be utilised for other smaller jobs. The Adzes and Axes just convert the unwanted timber into pieces only suitable for the fire. However, the bark would be stripped off for the tanners, as it contains tannin, especially if the tree had been an oak, alder or elm, and the bast fibres that lie just under the bark would also be pulled off to make rope and other ties. Willow, lime and again oak trees give some of the most useful bast fibres. And ultimately, any left over timber could be used in the Charcoal making process, or just burnt to keep the workers in the woods warm in the Autumn.