Re: polivinyl alcohol vs. gelatin sizing

From: Jack Brubaker <jack@jackbrubaker.com>
Subject: Re: polivinyl alcohol vs. gelatin sizing
Date: Sun, 31 Jul 2005 15:10:37 -0500

> The dilute mix of acrylic and water will grow mold. I add a very
> small amount of household ammonia to my dilute acrylic size and it
> keeps for years (without refrigeration). Do you see any harm in
> using ammonia? Can you suggest any other household chemical that
> might work better in your technical judgment?

Ammonia can provide viable nitrogen to bacteria and it is not a
substitute for biocide. It also changes the pH of the acrylic stock
upwards. High pH is not desirable for acrylic medium because the
emulsifier can degrade in that condition (e.g., acetate group can
become alcohol, upsetting the balance between them). Also, higher pH
may affect the process you are working with.

As I said in the previous post, there is no better choice than a true
biocide. Sodium salt of 2-phenylphenol can be easily purchased and it
is inexpensive, very effective and relatively safe (of course I
wouldn't bring it anywhere near food or drink but it was used on some
fruits). I've mentioned Bayer's "Preventol ON Extra" flake many times
on this list and you can buy it in a small bag from Kremer.

Trying to make inappropriate substitutes work is a good source of
unnecessary frustration and it is the easiest to get the right
chemical for each job.
Received on Fri Aug 5 12:01:56 2005