U of S | Mailing List Archive | alt-photo-process-l | RE: Gum Preservatives

RE: Gum Preservatives



This tip given to me by Sam Wang works fine when using thymol. Make a 100%
solution of thymol in isopropyl alcohol. I simply add a shooter of this to
the gum when I mix it up. The gum works great and smells like a fresh
Band-Aid  and never sours or molds.

Don Bryant


-----Original Message-----
From: Loris Medici [mailto:mail@loris.medici.name] 
Sent: Wednesday, December 06, 2006 12:49 AM
To: alt-photo-process-l@usask.ca
Subject: RE: Gum Preservatives

I wouldn't too. I used thyme water (which contains considerable amnt. of
thymol) in my first batch (3ml into 300ml) and the gum solution went bad
in just 2 weeks (serious mold growth). I used food grade Sodium Benzoate
in the second batch (according to the following recipe:
http://www.usask.ca/lists/alt-photo-process/2005/apr05/0247.htm. Please
note that I mean 5g Sodium Benzoate per 200g Gum Arabic powder. My
gum:water weight ratio is 1:2 - 100g gum powder into 200g/200ml water -
that's quite different from Guido's recipe!), and it's fine after 2
weeks - it looks, smells and works (and it works well!) just as it was 2
weeks ago... (I'm currently printing on aluminum)

Hope this helps,
Loris.

-----Original Message-----
From: Katharine Thayer [mailto:kthayer@pacifier.com] 
Sent: 06 Aralık 2006 Çarşamba 05:19
To: alt-photo-process-l@usask.ca
Subject: Re: Gum Preservatives

You could, but I wouldn't. What you need is a biocide, while glyoxal  
functions as a crosslinking agent.  If you used enough glyoxal to  
crosslink the gum enough to discourage mold growth, I suspect it  
would also render the gum insoluble (thus unusable).   In my  
experiments hardening gum for painting, I found that a drop of  
glyoxal hardened 5 ml of gum to a crystalline state. In general, I'd  
say you want the crosslinking of gum to occur in the exposure phase,  
not before.
Katharine

On Dec 5, 2006, at 6:31 PM, Michael Koch-Schulte wrote:

> Can I use a few drops of Glyoxal in gum arabic as a preservative?
> I'm mixing
> the gum from powder.
> ~m