Re: Found it! (salicylic acid) (fwd)

Terry King (KINGNAPOLEONPHOTO@compuserve.com)
Mon, 16 Jun 1997 03:43:03 -0400

Message text written by Judy Seigel
>
>Yes, Gloy is "said" to be faster than gum arabic, but in the, admittedly
>unsuccessful, tests I did with Gloy I found that it wasn't. At least it
.wasn't faster than the particular gum I was using at the time, nor even
.quite as fast.... Perhaps under a set of other variables it might be
>faster than gum arabic used with the same variables, but just hearing
>folks say it's "faster" is hardly conclusive. In fact I believe the
>one who started that story may have been Terry, but it turned out that he
>changed from potassium dichromate to ammonium dichromate at the same time
>he switched to gloy. Ammonium dichromate (saturated) is definitely faster
>than potassium dichromate (saturated).

It was a combination of the two. I undoubtedly got faster speed from the
ammonium dichromate but there apperaed to be a an added factor from the use
of the Gloy which also gave more consisitent results.

>As I recall Larry Shapiro also said he found gloy faster, but, again,
>faster than what?

That is a good question. Nobody has yet explained the purpose of this
discussion. What is the desired result from the slower gum.

>In any event, I've never seen it matter, since an exposure of 3 minutes is
>hardly a major advance on an exposure of 5 minutes. However in this case,
>for masking purposes, you're quite right, it does matter.

Slower gums can give marginally more subtle effects. This is an advantage
of gum

If we only seeking a gum as a mask I found it more effective only to coat
those areas of the print that one wishes to expose and not use a mask at
all. This is easy enough on a light box.

>I have not tried Le Pages glue, but I made a series of tests with
>rabbitskin glue.

The rabbit skin glue i know is a gelatine.

>Dick, it's not my *idea* -- it's my *finding.* If I solve the mystery
>I'll license it to you. ;- )

What is the mystery ?

Terry King