Early Plastic Imitations of Organics

Ever since they were invented, plastics have been used to copy organic gem materials.  Because they are light and warm to  the touch, plastics can make convincing copies of many of the organics, though some (such as coral or shell which are cold and heavy due to their mineral content), do not lend themselves to plastic imitations -- or simulants, as they are known in the gemmological world. 

 

On occasion a plastic imitation has had a fake structure added in manufacture, the better to copy ‘the real thing’, but usually the complete lack of any distinguishing structure is one of the clues that an item may be a plastic simulant.

 

But what constitutes a plastic?  What is it?  And what is an Early Plastic?

 

To quote the website of the Plastics Historical Society, www.plastiquarian.com, ‘When we talk of a substance being “plastic” (the adjective) most people would agree on its meaning. It can flow or be moulded, it is ductile or it can be shaped, but when we turn to defining “plastics” (the noun) we have problems. Almost any simple definition will exclude materials which everyone would agree should be included so we have to turn to scientific terms and start with the comment that plastics are all polymers (poly = many).’  A polymer is a very large molecule made up of many smaller units joined together, to form a long chain.

 

In the gemmological world we tend to use the familiar word ‘plastic’ rather than ‘polymer’, and, for the sake of simplicity, we shall continue to do so in this article.

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Vulcanite pendant, simulating jet.

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Bois durci plaque of Napoleon

Shellac Union case

There are natural plastics which include shellac, keratins such as tortoiseshell, horn and baleen, and some tree resins (ambers and copals). (See 'A Background to Amber', 'A Background to Horn', 'A Background to Tortoiseshell', and 'Keratins'.) These are all organic gem materials, and for many centuries they have been processed with heat and pressure to produce items such as jewellery, trinkets, combs, and so forth.  With the possible exception of amber and copal, which can be ground to powder or chips and manufactured in exactly the same way as modern plastics, in large machines and with little (if any) hand-crafting, the natural plastics need to be fashioned by hand, even though they can be shaped rather than carved.  This adds greatly to the cost of manufacture.

A change came in 1843 when vulcanite (also known as ebonite, or hard rubber) was patented.  Vulcanite is natural rubber which is cured with sulphur, so some people consider it to be a natural plastic, while others insist that it is the first semi-synthetic plastic.  The material was being developed simultaneously in both England (by Hancock) and in the United States (by Goodyear), and was finally patented by both in mid-1843.  It was used for tyres, smoking accessories, false teeth and various small items including jewellery.  With black dye added it became one of the best-known jet imitations.  Vulcanite does not degrade, but its colour fades to dark khaki.

Shellac was the next semi-synthetic to be invented, in 1856.  It is made from a secretion of the lac insect, Coccus lacca. The secretion is clear brown and brittle when hardened, so a filler (wood flour or a metallic filler) was added, together with dye, resulting in a darker, opaque material.  Shellac was used to make hand mirror and hair brush backs, union cases, i.e. the closing photographic frames used for Daguerrotypes (the early silver nitrate coated copper photographs) which faded if left in the light, and early gramophone records.  It does not degrade but it can become increasingly brittle.

Bois durci was developed in France and also patented in 1856.  The natural part of it was blood -- originally from a Parisian abatoir -- which, like shellac, had to be mixed with a filler plus a dye.  Usually coloured black it was made into items such as commemorative plaques and inkstands, and other medium-sized artifacts.  It was very seldom used for jewellery.

In the mid 19th century many experiments were under way, using all manner of materials and trying to turn them into something that could be shaped and moulded.  Among the raw materials tried can also be mentioned ground leather and a variety of plants.  Papiér maché was developed and had some success.  It could be coloured, painted, inlaid, and used for small objects and even some furniture.

A true breakthrough was the invention of cellulose nitrate.  Again, it was a semi-synthetic, combining cellulose (in the form of cotton fibres) with nitric acid and camphor.  It was first presented by Alexander Parkes in England in 1862 as ‘Parkesine’, but it was not stable and tended to warp.  After that it was perfected by two gentlemen (Spill and Hyatt), living on either side of the Atlantic, who carried on a legal battle over copyright until one of them died.  Known variously as Xylonite, Zylonite, Ivoride, and the best-known name, Celluloid, it was used to make a multitude of things, from false teeth, dolls, and collars and cuffs, to boxes.  It made an excellent imitation of ivory, coral, tortoiseshell and even -- with the addition of mica -- mother-of-pearl.  Celluloid is one of the plastics that can degrade suddenly, giving off a small of camphor. (See 'A Background to Tortoiseshell'.)

The main drawback of celluloid was that, because it was made with nitric acid, it was highly combustible.  In 1894 cellulose acetate was developed as a safer alternative, and was widely used in jewellery, also to copy organic gem materials such as tortoiseshell.  In the late 1920s a method of production called injection moulding was developed, which meant that some materials – such as cellulose acetate – could be mass produced in moulds instead of cut out of sheets or rods.  Brooches, bangles and linked chains were popular, and the jewellery was often hand painted.  Cellulose acetate fashion jewellery is still in production today, notably in France.  Cellulose acetate can also suddenly degrade, giving off a smell of vinegar.

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Celluloid imitating coral (left), and tortoiseshell (right).

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Degraded celluloid 'tortoiseshell' box. Metal hinges have caused it to turn green.

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Powder compact in plastic simulating mother-of-pearl. Now warped and discoloured.

Casein was invented in Germany in about 1900.  It was produced under the name Galalith, and as Erinoid in England.  Made from curds from skimmed milk and formaldehyde, it could, like celluloid, be produced in any colour, also with patterned and pearl effects.  Casein is widely accepted as the most beautiful of all the early plastics.  As with celluloid, it was used to copy tortoiseshell, ivory and mother-of-pearl, and also in its own right.  Unusually for an early plastic, old examples may craze and crack but seldom degrade completely.  (See 'A Background to Ivories')

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Casein simulating ivory beads. Note the artificial 'structure' of the material imitating elephant ivory.

Phenolic was the first totally synthetic plastic to be invented.  A mixture of carbolic acid (phenolic) and formaldehyde, it was invented in 1907 in the United States by Leo Baekeland, and became known as ‘Bakelite’.  The name should refer only to the original material, but tends to be used generically – especially in the gem world.  True ‘Bakelite’ contains a filler (wood flour, paper, fabric), to make it stronger and more stable.  As a result it was produced in opaque, dark colours.

Cast phenolic tends also to be called Bakelite (incorrectly), though it is made without filler and used for small items, notably as an amber imitation, both in clear golden and red colours.  It was especially popular as an amber simulant in the 1930s.  Phenolics are still in production today.

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'Bakelite' jewellery, or, more correctly, Phenolic bangles (left), and Cast Phenolic beads, often called cherry amber (right).

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In the 1920s urea formaldehyde was put into production.  It was similar to Bakelite but it could be made in pale colours.  It was used as an ivory imitation, but came into its own as kitchen ware, called Bandalasta or Beetle ware.  Urea formaldehyde tends to warp and may crack.

The 1930s saw the invention of plastics as we know them today.  Polystyrene, polythene, acrylic and nylon all came on the market, and since then many, many more plastics have been developed.

CARE OF PLASTICS

Plastics are not indestructible, indeed some early plastics tend suddenly and without warning to degrade, and then fall to pieces.  When degradation has started there is no cure.  It is therefore advisable to protect the materials in the hope of preventing the problem. Any metal in contact with the plastic will also become contaminated by the vapours. (See photo above of imitation tortoiseshell box.)

If any signs of imminent degradation appear, the item should be removed from the vicinity of other items and stored on its own, as the effects are contagious and will cause other similar items to start to degrade too.

Other early plastics may crack, craze, warp, and discolour with time.

The following tips may help to protect items made from an early plastic:  Store them away from bright light and heat, preferably in a cool, dark place.  They should not be sealed in containers but kept in a dry, ventilated place.  If wrapping them up, ensure that acid-free tissue or similar is used.  Keep them clean, but do not attempt to clean them with household cleaners.  In jewellery, avoid contact with hairspray, perfumes and cosmetics.

QUICK REFERENCE CHART

MATERIAL            MAIN CONSTITUENTS           COLOURS & OPACITY             GEMS COPIED

Vulcanite              Rubber cured with sulphur     Black. Opaque                              Jet

Shellac                  Insect excretion + filler           Black, brown red. Opaque           Jet

Bois durci              Blood + filler                            Black. Opaque                              Jet

Cellulose nitrate (‘Celluloid’)   

                      Cellulose + nitric acid + camphor    All colours+Opaque+Pearly       Ivory, coral, tortoiseshell, mother-of-pearl

Cellulose acetate

             Cellulose + acetic acid + sulphuric acid  All colours+0paque+Pearly        Ivory, coral, tortoiseshell, mother-of-pearl

Casein              Milk curds + formaldehyde          All colours+Opaque+Pearly        Ivory, coral, tortoiseshell, mother-of-pearl

Phenolics  (‘Bakelite’)

               Phenolic + formaldehyde + filler          Dark colours+Opaque+Mottled.    Tortoiseshell, wood

Cast phenolic

               Phenolic + formaldehyde                 All colours. Transparent or opaque    Amber, ivory, coral, tortoiseshell

Urea formaldehyde    Urea + formaldehyde         All colours.  Opaque                     Various

 

 

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