Originally Posted by Pinhead-227
Toothpaste works very well as the final lapping compound. Makes the copper nice and shiny!
Toothpaste has silicon dioxide (sand) in it, btw.
Silicon dioxide WILL work by using toothpaste, but I wouldn't recommend it.
First, toothpaste has very little of it in there. Secondly, silicon dioxide just flat out isn't very hard. As an abrasive grit, it is soft, weak, and has boor cutting properties. And additionally, the halogen compounds in the toothpaste (flourides) can be detrimental to some metals, they are very active chemically.
As you might have guessed, "sandpaper" hasn't really used true sand in quite a few decades. The premium abrasives are diamond, boron carbide, silicon carbide, and aluminum oxide. Silicon carbide has a "friable" grain structure that continually breaks down under pressure, exposing new cutting edges - abrasives of this type provide a very consistent and clean cut. It is very commonly used in metalworking for this very effect.
Aluminum oxide is much tougher, and doesn't break down - it "wears smoother" compared to silicon carbide. Aluminum oxide paper will generally last longer but it will wear, providing a smoother cut the longer you use it. Carborundum is made of aluminum oxide and is one step below diamond on the hardness scale.
Both types have advantages and disadvantages. But stay away from paper that uses flint, garnet, and silicon dioxide.