Alexei Volkov
Ivory is a valuable material that comes from the tusks and teeth of animals such as elephants, whales, hippopotamuses, and wild boars. Due to its value, ivory is often imitated using plastic. To distinguish between ivory and plastic, one can use the hot pin test, which involves heating a needle until it's red-hot and pricking the material in question. If the needle goes in, it's plastic; if not, it's probably ivory or bone. However, this test is destructive and may damage valuable pieces. Less invasive methods include using one's sense of touch, as ivory is usually heavier and feels colder than plastic, and visual inspection, as ivory has a unique cross-hatching pattern when magnified.
| Characteristics | Values |
|---|---|
| Weight | Plastic is lighter than ivory. |
| Heat test | Heat a needle until it's red-hot and then prick the item. If the needle goes in, it's plastic; if not, it's probably ivory or bone. |
| Touch | Plastic will feel warmer than ivory. |
| Visual | Plastic has a repeating grain pattern, while ivory has random grain lines. |
| Visual | Plastic is non-descript under magnification, while ivory has visible cross-hatches. |
| Visual | Ivory has circular rings, similar to the rings of a tree. |
| Visual | Plastic has a noticeable seam. |
| Visual | Genuine ivory usually fluoresces white under a black light. |
| Visual | Elephant ivory has a unique pattern of cross-hatching (Schreger Lines) that appear in cross-sections of elephant tusks. |
| Sound | Tap the item against your teeth. Plastic sounds more "plasticky." |
| Feel | Ivory and bone are very smooth to the touch and feel substantial, hard, and durable. |
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What You'll Learn
Use a black light test to rule out plastic
When trying to distinguish ivory from plastic, one of the tests that can be performed is the black light test. This test is also referred to as the ultraviolet light test. It is important to note that while this test is excellent for confirming that an object is made of ivory, it does not help identify the type of ivory.
To perform the test, purchase a black lightbulb or a black light flashlight. The test works best in a dark area. Avoid looking directly at the light. Ivory will usually fluoresce white under a black light, but this can vary depending on whether the ivory has a patina. Most old patinas fluoresce a dull yellow or brown. Be suspicious of any bright fluorescence as this indicates artificial aging.
Virtually all plastics and resins fluoresce blue or blue-white under long-wave black light, regardless of the surface colour in ordinary light. Therefore, the black light test is an important first step in ruling out artificial materials. However, it is not the only test that should be performed, as bone, vegetable ivory (cellulose), and glued-together ivory dust react like genuine ivory under black light.
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Examine the surface structure and smoothness
When examining the surface structure and smoothness of an object to determine if it is made from ivory or plastic, there are several key characteristics to look out for. Firstly, it is important to note that ivory is formed by living, growing tissue, resulting in unique grain structures that cannot be duplicated in artificial substances like plastics and resins. The grain structures in natural ivory are random and irregular, while artificial ivory often exhibits a repeating grain pattern with uniform, even lines.
To examine the surface structure, use a handheld magnifying glass to closely inspect the object. Place the object on a flat surface and hold the magnifying glass a few inches away, adjusting the distance as needed to focus. Look for the presence of pores or lines on the surface. Bone, for example, typically exhibits pores or small holes, while ivory often displays straight, cross-hatched, or swirled lines known as Schreger lines. These lines are the cross-sectional patterns that resemble the face of a two-by-four. Additionally, ivory tends to have a significant lip on its front, which can make it more prone to chipping.
When assessing smoothness, run your finger over the surface of the object. Ivory, along with many types of bone, typically feels very smooth to the touch and is substantial, hard, and durable. Plastic, on the other hand, can vary in smoothness depending on its type and purpose. For example, plastic piano keys are designed to have a specific texture that provides consistent friction and reduces light reflection. In contrast, plastic keytops may be highly smooth and mirror-like, especially when cleaned and free from blemishes or variances in colour.
It is worth noting that some plastics, such as Ivorite, are modified to feel more like ivory. These plastics aim to mimic the friction and texture associated with ivory while still retaining the flexibility and ease of manufacturing that plastic offers. Therefore, when examining surface structure and smoothness, it is essential to consider other distinguishing factors, such as weight, colour, and the results of non-destructive tests like the hot pin test.
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Weigh the item—ivory is heavier
Weighing an item is a good way to determine whether it is made from ivory or plastic. Ivory is heavier than plastic, and this difference in weight can be a distinguishing factor. Ivory, which comes from the tusks and teeth of animals like elephants, hippopotamuses, and whales, is heavier than plastic. However, it may take some practice to get a feel for how much an ivory item should weigh. Jeanenne, an expert from Skinner Inc. in Boston, notes that you can ask to hold an item in an antique shop to get a sense of its weight.
It is important to note that while bone and ivory can be similar in weight, ivory tends to be more valuable and highly regulated. For example, African elephant ivory is only legal for sale if it was imported before January 18, 1990.
When comparing ivory to plastic, it is worth mentioning that celluloid, a type of plastic, is noticeably lightweight and translucent. On the other hand, Bakelite, another type of plastic, can be heavier and resemble genuine ivory in weight. Therefore, weight alone may not always be a definitive indicator, and other tests or observations may be necessary to distinguish between ivory and certain types of plastic.
In addition to weighing the item, you can use other non-invasive tests that utilize your senses. For instance, you can tap the item against your teeth—Jeanenne claims that she can immediately tell the difference between the sound of ivory and plastic. You can also try touching the item, as plastic will feel warmer than ivory.
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Look for cross-hatching under magnification
When trying to distinguish between ivory and plastic, magnification can be a very useful tool. Under magnification, plastic is usually non-descript, whereas ivory will often display a fine grain. Ivory from elephant or mammoth tusks will have fine lines on the surface called "Schreger lines", which form a cross-hatch or diamond pattern. These lines can appear in a variety of ways, including straight, cross-hatched, or in a circular motion. The presence of these lines is a good indicator that the material is ivory, as plastic will not usually display such features.
To further confirm that the material is ivory, you can measure the angles of the Schreger lines with a protractor. Angles less than 90 degrees indicate mammoth ivory, while angles above 115 degrees suggest elephant ivory. It is important to note that the lines are best seen under polarized light, so using a photocopy machine or similar tool can be helpful.
In addition to examining the surface structure, magnification can also be used to inspect other features such as colour and weight. Genuine ivory usually fluoresces white under a black light, although this can vary depending on the patina. Most natural old patinas fluoresce a dull yellow or brown. On the other hand, synthetic materials tend to absorb more light and appear dull. While it is rare, some replica materials might also appear white under a black light, so it is important to perform multiple tests to be sure.
Another visual test that can be performed under magnification is to look for pores or tiny holes. The presence of these pores is a strong indicator that the material is bone rather than ivory or plastic. These pores, called Haversian System holes, can be seen with a magnifying glass or even with the naked eye.
It is important to note that magnification is just one tool in identifying ivory and that multiple tests should be performed to make an accurate judgement. Other tests that can be used in conjunction with magnification include the UV light test, the weight test, and the hot pin test. By using a combination of these tests, you can more confidently distinguish between ivory and plastic.
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Perform the hot pin test (but this may be destructive)
The hot pin test has been used to distinguish between ivory and plastic for as long as plastic has been made to look like ivory. However, it is a destructive test and may damage or ruin the value of the piece being tested. It is therefore recommended that non-invasive tests are tried first.
To perform the hot pin test, heat a pin until it is red-hot and then touch it to the piece in question. If the pin sinks into the item, it is not ivory. A hot pin will not penetrate real ivory, although it may leave a small mark that is hard to see. Ivory will also smell like burning hair when touched with a hot pin, whereas plastic will smell like burning plastic.
The hot pin test can be used to detect synthetic ivory, but it is not recommended for valuable items. This is because the test can char and damage the piece, and it also does not tell you the type of ivory you are looking at.
As an alternative to the hot pin test, you can use a UV light to distinguish between ivory and plastic. Ivory will glow bright white under UV light, whereas resins and plastics will appear dull or fluoresce blue or blue-white.
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Frequently asked questions
Ivory is typically heavier and smoother than plastic. If you suspect an item is ivory, you can test this by picking it up and feeling its weight. You can also run your finger over the surface to check for smoothness.
Ivory will often show cross-hatching or Schreger Lines under magnification. Plastic, on the other hand, will appear non-descript.
The hot pin test involves heating up the point of a needle until it's red-hot and then pricking the item in question. If the needle goes in, the item is plastic; if not, it's probably ivory or bone. However, this test is destructive and not recommended by experts.
Yes, you can use a black light as your first test. Virtually all plastics and resins fluoresce blue or blue/white under long-wave black light, regardless of their surface colour in ordinary light. Genuine ivory usually fluoresces white, but this can vary depending on the patina.
