Quote Originally Posted by Photo Engineer View Post
Hot caustic soda will etch glass.
That's interesting. I have to admit that this was taken from old books; I had not tried it. I wonder if they just didn't worry about the etching, as they were contact printing anyway.

Perhaps, too, you could throw more light on something else I have read in old books but never verified. It is that you sometimes get a residual ghost image on (or perhaps more accurately in) the glass even when the gelatine is fully removed. Hard to believe, but I have seen it asserted in more than one old source (sorry, can't remember where).