You have been given excellent advise/observation s by the Forum members posting above. Indeed. primum non nocere.   That being said, it is possible to prep such a piece in a "low-tech" manner. I have had success with eggs using the following simple approach. It requires time and patience.    I utilized the curved surface (not the point) of a C-shaped dental pick to gently abrade the thin matrix coating away. The matrix was dampened with a moist paper towel and the powdered ma