Is hydrofluoric acid attacking glass and etching designs in glass a physical change?
No, it is a chemical change. The glass is changed into new substances where it is etched.
Things found in etching creams: Barium Sulfate, Sulfuric Acid, Sodium Bifluoride, and Ammonium hydrogen difluoride. Hydrofluoric acid is the main ingredient that will etch glass. Overall, the cream is a diluted form of hydrofluoric acid. It's not nearly as dangerous as pure hydrofluoric acid but still, be very cautious when using it.
Hydrofluoric acid may cause severe damage because of its exceptionally corrosive nature. For instance, one may get a bit of the acid under a fingernail. and hydrofluoric acid (see related link) can eat clear to the bone. Hydrofluoric acid's fumes can damage or destroy the cornea. More than a few people have lost their lives to hydrofluoric acid.
David Deuchar has written: 'A collection of etchings after the most eminent masters of the Dutch and Flemish Schools particularly Rembrandt, Ostade, Cornelius, Bega, and Van Vliet' 'A collection of etchings, after the most eminent masters of the Dutch and Flemish schools' -- subject(s): Dutch Etching, Etching, Etching, Dutch, Etching, Flemish, Flemish Etching
If the etching is one of a kind, I recomend looking for the name of the artist on the etching. If there is a name, you can look up the artist and get a general idea of what a piece of his/her art is worth. If there are more than one sculpture/etching of this same theme. Try to find the price or value of the other.