[This compilation of information about testing materials for authenticity has been compiled and edited by me from the following sources.
Bly. J. Is It Genuine. 1986. Mitchell Beazley. London
Luigi Vecchia. The husband of an Arachne member in Italy.
Big Book of Buttons by Elizabeth Hughes
Quite a lot of input by Ann Kovalchick including the article on Bakelite, and the information on tortoise shell]
Firstly there is a potentially destructive test.
Basically bone "burns" Ivory does not. Put a lighted match to the objects! Ivory will not really be effected by it. It just goes black and you can wipe it off. (That is unless you really subject it to a lot of heat). Bone will have a good shot at burning and will have the flesh smell. The object might be physically damaged by the experience.
The red-hot needle test is less destructive. With this you push the red-hot needle into the object where it will not show. With bone it will enter more easily and burn with a smell of flesh, with ivory it will be harder to push it in and it smells like the burning caused by a dentist's drill. The opinion of most people is, "do not attempt this test."
Secondly test of the visible differences.
Basically tusks (Ivory) are teeth (incisors from the upper jaw.) They are therefore made up of dentine as opposed to the softer material of bone.
The visible structure comprises many many minute longitudinal tubes, which when fresh are filled with oil. It is this oil that gives it the polish and the very gradual loss with age. Bone on the other hand is has all its "fat" boiled out before being turned.
So, you should offer the ivory to the light and look for faint longitudinal lines and then revolve the bobbin, very slowly, through 90 degrees. These lines should, on revolving, become less pronounced or even disappear from the angle at which you are observing them. (If the ivory is simulated i.e. casein based compound the dark/light lines will remain and they are more pronounced on the simulated ivory. You will need to practice this to "see" what the description is saying.
The characteristic of bone is that it is provided with a blood supply and therefore has minute pores (which are the channels through which the bone is kept alive) They look like tiny brown or black spots (or channels depending on the angle of the turning.
Bone's black or brown flecks (channels) are reasonable visible *without* a magnifying glass. But remember sometimes the bone has been bleached so that the black or brown flecks are not so easily visible, but you can still see the channels etc if the light is good. It is probably better to use a magnifying glass.
So to sum up. Ivory has longish lines (tubes). Bone has black or brown flecks (channels) you will need a good light source to see the lines (tubes) on ivory but the flecks are reasonably visible with a magnifying glass in bone.
Other plastics chip like glass and feel warmer than true ivory.
Another method to tell bone and ivory from other materials without the hot needle or burn test seems to be the taste or click your teeth test. Just like you can tell a glass or porcelain cup from a plastic cup.
Walrus tusk is hard to distinguish unless part of the object has a cross section of the tusk being used. If so the core is granular dentine not hard like the true dentine.
Basically it comes down to if you want to tell the differences between bone and ivory, don't bother with hot needle or burn test. For the person who can't visually tell the difference, the burn test is a good way to ruin what you have!
Ivory
I don' t know any way to distinguish between ivory from elephants, mammoth (fossil ivory), hippopotamus and sea elephant. The only difference I know is that ivory from hippopotamus, considered the finest, can only be used for small objects. Another aspect is that elephant' s fang grows like tree-trunk, forming a series of concentrical rings (not too regular, often they appear elliptical) that can be evidenced at low magnification (10-20 x) with a good lens (or better a stereomicroscope) and lateral light, incident from small angle. This characteristic can be used to tell elephant's
ivory from other materials.
Artificial Ivory
The rings can be mimed, but they are too regular; there are chemical tests (using organic solvents) that can tell the difference.
Narwhal tooth (Up to 2 m long, diameter up to 3 cm) It can only be used for long and thin objects; generally (if the object is not too little) you can see the vascular canal at one end of the object.
Bone and Horn They show (under low magnification, in the conditions of light as ivory) several nervous and vascular canals (i.e. darker and long strips or lines). The material is also less compact and elastic, more opaque and not so heavy as ivory (because they are more porous).
The "match test" indeed is quite drastic but definitive. The smell of burned hair, (horn), flesh (bone ) or plastic (plastic "chemical") The definitive test could be immunofluorescence with monoclonal antibodies, but I don' t if there is a commercial source and it requires a complex instrumentation (fluorescence microscope)." (LV)
The earliest synthetic plastic as celluloid discovered in mid 1850's but developed in the early 1870 by John Wesley Hyatt from nitro-cellulose and camphor. He hoped to find a material for billiard balls. But the celluloid he found was too brittle, but by the end of the century was widely used for all sorts of household items including buttons and shuttles.
Bakelite, a phenol compound was discovered by Leo Baideland in 1907. Dr Baekeland, in a makeshift laboratory in the back yard stable at his home in Yonders, New York, was trying to produce synthetic shellac. He combined phenol (carbolic acid) with formaldehyde and found the mixture refused to be poured from his test tube. Because he was not one to throw away a test tube, he was determined to clean it. But even with heat and a series of solvents, it did not work. The material was petrified. Even though he failed to find shellac, he was excited by what he had found, or as it turned out, the first thermosetting plastic.
In 1910, Baekeland formed the General Bakelite Company. There are two types of Bakelite, molded and cast. The early molded type of phenolic resin was mixed with fillers as wood flour and asbestos for added strength which made it dark in colour. The cast without the fillers had better decorative and colour properties and did not require expensive molds and equipment. They were cast in liquid form, hardened, cooled and converted to goods by machining.
Bakelite became more widely used after the patent expired in 1926 when other firms began to improve and market it under names especially Catalin. This newer phenol compound took colour better and was very attractive. It came from the factory in tubes, rods and sheets of various lengths and sizes. It was then easily worked, it could be sawed, sliced, ground, drilled, sanded and carved into intricate shapes. it was then polished in big rolling tumblers. This is the material we not tend to call Bakelite and it is material of some of the most beautiful "plastic" buttons.
The overall industry made great gains in the 20's when a German chemist, Hermann Standinger recognised the nature of the substances as giant molecules he named polymers. From this, the rest of the industry developed, and there appeared acrylics such as Lucite and plexiglass and then nylon in 1940.
This was sent to me by an Arachne member and acknowledged with thanks.
Horn can be identified by the highly characteristic smell of burning hair or feathers.
Celluloid smells like camphor, usually a very strong smell. I think you probably will know the plastic smell.
Casein is easily tested with a hot needle. The needle will go in and there will be the smell of burnt milk.
The hard plastics like Bakelite react like bone, a hot needle won't penetrate and it doesn't burn very hot there is a chemical smell. But Bakelite won't have the markings that bone or ivory has. Also the taste test give a pretty good clue.
The fact is that which ever method you choose to tell bone from ivory it requires a fair amount of hands on experience. Always assume bobbins and sewing tools are bone unless you have *very* good reason to believe otherwise.
Written by Brian Lemin, November, 1998.
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