Why the 'Tooth Test or Grit Test' For Pearls Is False
First, stop...just stop quoting and using the 'tooth / grit / resistance test on pearls as how to identify them. Here's why. The pearls shown are smooth and glassy, they are also waxed and polished so the nacre is no longer gritty but they are a strand of $4,000 Japanese Akoya cultured pearls and not 'fake' as the grit test result indicates.
The often repeated question, "are my pearls real or fake?", is one of the top jewelry questions if not the #1 asked in jewelry forums and pages all over the internet. It is followed up by the #1 response of do the 'tooth test' which is also known as the 'grit test' or 'friction test'. If your not familiar with what that is, then you either don't have pearls or never asked the question of what kind of pearls you have. First before going any further there is a translation between what the public uses for pearl terms and what the jewelry trade uses. To eliminate confusion, the public and sites that want to use terms that the general public will recognize, use the descriptive terms of 'real' and 'fake' for pearls. The jewelry industry goes by 'cultured' or the rarer 'natural' pearls in place of 'real' and 'simulated' or 'imitation' in place of 'fake'. For making this easier to follow I will continue using the general public's use of the terms 'real' and 'fake' even though those are terms I would never use otherwise.
The test is where you either rub two pearls together or rub a pearl on the sharp edge of your tooth. The theory of this test is if you feel a resistance when you rub two pearls together or feel a gritty resistance against your tooth, it means they are 'real' pearls. If the beads glide smoothly against one other or slide over your tooth edge with no gritty resistance, it is supposed to mean they are 'fake' pearls.
Where this test is best used when its done as a secondary test in combination with high magnification and not relied on solely as the only source of identification. The reason this is the most unreliable test to use solely for determining both types of pearls is that the test results are being over simplified on a very complex product. There are many reasons why the results are completely false. Did you know that 'fake' and 'real' pearls can both have coatings and treatments that make the surface test completely the opposite of what they are testing to be? Most people that are familiar with the test have heard that there can be gritty coatings on 'fake' pearls that mimic the grit and resistance giving a false positive test result of 'real' pearls. What is never mentioned and not even widely known unless you deal with pearls in the industry is that for the past 20 to 30 years pearl harvesters have applied treatments to improve surface imperfections and give a higher luster that make lower quality 'real' pearls have a smooth glassy surface by covering over the gritty nacre layer. Doing this artificially improves a cultured pearl's surface imperfections and gives the impression of higher luster and a better quality pearl than it actually is. Another popular treatment is lacquering the surface of a 'real' pearl of lower luster to make it look like it has a higher luster. However the layer is not permanent and can show a peeling of the fine layers over a short period of time. These coating enhancements, both the polished wax layer and the lacquered layer makes the pearl's surface slippery and glassy with no resistance, the coatings cover over the gritty texture and will give a false result on a 'real' pearls being misidentified as 'fake' pearls.
For best identification practices for the most accurate results always do a couple different tests before making the judgment call. Study on learning how to identify pearls from magnification (the higher the better, 50x is recommended) as the first main test being the most important deciding factor...even then, if your not regularly dealing in pearls take them to someone who does for an experienced 2nd opinion, as pearls are among the most difficult items to properly identify even by the professionals. The difference in a wrong ID can be thousands of dollars your loss if you misidentify a strand of Akoya or South Sea cultured pearls as 'fake' because they feel smooth by the tooth test.
Fortunately there will always obvious imitations that you don't even need to test because they are obvious by sight examination alone. The more pearls you handle and examine, the easier it becomes to identify. There are treatments to luster though that are much harder to spot. If the strand is not obvious to being 'fake' pearls then your go to method to test should be high magnification of the recommended 50x over the resistance/glide test which you can now see why it can go so wrong if it's all your relying on. Now happy hunting on finding all those misidentified 'real' pearls that were tagged as 'fake'!
Some links that describe the waxy, polishing and lacquering treatment processes:
https://pearlwise.pro/types-of...
https://www.pearl-guide.com/th...
How to properly test your pearls with pearl industry mention that the much used tooth test is unreliable.
https://www.jewellerybusiness.com/features/detecting-pearl-imitations-and-treatments/
