I not an expert but this sounds not true.
Also, I will like to point out that the Casino Royale chips is Plastic Slugged and not Clay like material like th ePaulson Clay that u often seem in Casino.
Composite Clay is a fake term invented by those mass market sellers and just means Slugged Plastic in reality
Okay, forget about it... Let's put it this way: china-made chips' materials may be softer or harder, no matter the declared material (ABS, China Clay, etc).
Cartamundi originals are made with a way softer material than apache poker Casino royale ones.
And so, on Cartamundi you must use the black or green sponge at best.
On the other side, Apache poker Casino royales are very different and made using a way harder material, so you must use a faster speed, or a lower grit sponge, or both...
Very important:
By using this tecnique, you can only fix defects caused by material in excess (by removing it), meaning in those spots where
one color was dragged over the other (see the photos I posted once again, and try to understand that).
All you have to do is to remove the upper color, then the one below gets back to the surface, and the job is done.
...But...
But sometimes the defect is INSIDE the chip (rather than OVER the chip), requiring so much digging that trying to fix it will make no difference and possibily ruin the chip.
It takes a little time to start adapting the eye to the two kind of defects.
Also, never stop the spong over a single spot, alway move it back and forward: you don't want to dig, you want to polish and reshape, polish and reshape, polish and reshape. You do it enough times, and you reach perfection
Should I write a complete guide, lol?