Re: alum as paper size
Thu, 27 Jul 1995 23:02:16 +0300
>>From: David Soemarko <email@example.com>
>>On Wed, 26 Jul 1995, Luis Nadeau wrote:
>>> Alum cannot be used in place of gelatin size. It can be used to harden (or
>>> tan) gelatin and then can be washed out but it cannot replace gelatin since
>>> it is not a colloid and it is for this purpose that we need gelatin in the
>>> first place.
>Maybe I understand the way it works incorrectly. Somehow I thought that
>since the gelatine was hardened, it trapped the alum in it so the alum is
>no longer water soluble? How can the alum be washed out?
Alum being water soluble, can be washed out. Alum is not a solid pigment
trapped in the gelatin as in a carbon print.
Fredericton, New Brunswick, Canada