RE: Gum Preservatives
Yes, I'm sure that this works perfectly (IIRC, Christina Anderson and David Hatton - and probably many other gum printers around - also use pure Thymol to preserve gum). Probably other impurities in thyme water caused my gum go bad. I probably would use Thymol if I could locate it easily but, in my case Sodium Benzoate was obtainable more easily and it was cheaper than pure Thymol crystals. Regards, Loris. -----Original Message----- From: Don Bryant [mailto:dsbryant@bellsouth.net] Sent: 06 Aralık 2006 Çarşamba 08:13 To: alt-photo-process-l@usask.ca Subject: 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
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