Diamond tester shows ceramic case is softer than expected

[mysterio 18]

Well, this was posted in the Exile forum and did not want this to disappear when the main forum comes back up.

This was posted by someone named Celestial (not sure if the same member as here who so far only has 1 post). He says

Quote

Hi guys, not sure if this topic has been discussed previously. I tried but was not able to find any info. There are threads discussing the hardness of the PAM441 case and how scratchable it is, and the conclusion is that the case is made by it's 9, only next to diamond... meaning that only materials like diamond can cause a scratch on the case. Out of curiosity, I tried to measure my VSF v2 PAM441 with a diamond selector . Just like how it is shown in the videos, both of the crystals have (Mohs) hardness of 9, but the case reads only 5-6, which is the same with glass and softer than quartz, which is omnipresent in the environment. Meaning it can still be scratched easily by a lot of things during everyday activity. I wonder if experts like you have any comment on this?

Here is my reply:

TLDR, it's a crystal tester, not a hardness tester.

TSWM, A diamond tester, like the one pictured by the OP, uses a thermal conductivity method to determine if the crystal being tested is a diamond, as heat passes through crystals differently based on their crystalline structure. That's how we can use it to test if the crystal on our watches is sapphire (or corundum) or not (which is a 9 on the Mohs' scale of hardness compared to diamond's 10). This is also why this tester cannot be used to test for moissanite (it's actually a 9.5 on the Mohs' scale), which conducts heat in a similar way to diamonds so you need another tester which uses electrical conductivity to test the crystal.

To test for hardness, you would need another tester, basically a whole different set of tests, something you can check on google if you wish to know more. Then you can check where your material is on the Rockwell or Vickers Hardness Scale. Interestingly enough, precious metals are not only found on the Rockwell Hardness Scale but also on the Mohs Scale which is the primary reference for jewelers.

Now where does the Ceramic used in Panerai watches lie in the hardness scale? It's 1700 HV (Vickers Pyramid Number). In comparison, Zirconia which is usually used in other ceramics, is only 1400 HV. Correlating those values to the Mohs scale (there is no exact conversion but there was a study done to correlate the two), it would be slightly higher than Topaz which is 8 on the Mohs scale (1648 HV) but lower than Sapphire which is 9 on the Mohs scale (2720 HV).

There you go.

 

[Glaude 1,615]

Saw the thread title, saw the well-respected member posting it, wasn't expecting anything than a good debunking !

Thank you mysterio.

If I may add : you can get those "Diamond selectors" tell you what you want if do not "calibrate" or more precisely, scale them, properly, just turn the Volume dial up and there you go : a magnificent simple glass showing at a solid 9 !
It's also important to specify that the Rockwell scale is not a way to tell which type of metal is used, but only the actual hardness of the metal you are testing. You can find different metals at the same hardness and a single type of metal with different qualities can show different readings on the Rockwell scale.