>
>>From: Richard Sullivan <<richsul@roadrunner.com>
>>Subject: Re: Gum consistency and preservatives.
>>
>>>Date: Tue, 17 Jun 1997 21:44:15 -0400 (EDT)
>>>From: Judy Seigel <<jseigel@panix.com>
>>>Subject: Re: Gum consistency and preservatives.
>>>To: alt-photo-list <<alt-photo-process-l@skyway.usask.ca>
>>>Errors-to: jseigel@panix.com
>>>Comments: "alt-photo-process mailing list"
>>>
>>>
>>>
>>>On Tue, 17 Jun 1997, Art Chakalis wrote:
>>>> I use thymol in place of mercuric chloride. However, if you mix your own
>>>> gum solution you also need to keep it heated for a period of time to
>>>> destroy any enzymes that are found naturally in gum. However, too
>>>> much heat will degrade the gum itself. I typically heat to 140 F for
>>>> about 1/2 hour to deactivate the enzymes.
>>>
>>>Art, I happened to be in TALAS today, which has conveniently moved next
>>>door to my storied gym, buying various goodies (including TA DA! the
>>>Dahlia mister!!!) and asked about heating the gum arabic. Experts there
>>>had never heard of it, nor have I come across a mention of same in 97
>>>years of the "literature" on gum printing. I was advised to ask you, sir,
>>>for your references!!!
Sounds to me like he is "pasturizing" it. Whether it is destroying enzymes, which it very well may, or is killing bacteria which is also a possibility, his heating process sounds plausible. His use of thymol would certainly kill any bacteria. However, I would like to know if the gum undergoes any heating in its original processing, if so it would probably make his heating redundant. I have gotten gum in the past which when mixed left quite a bit of dirt which settled to the bottom. I have a long paper from the Sudanese government on gum arabic on my web site under processes:gum and it describes quite a few different grades, but none are cleaned in any manner, just graded at the source on various criteria.
Since much gum today is destined for use in food products, I would expect some kind of filtering and cleaning to take place after importing it in order to meet food safety standards. The most likely method here would be to dissolve it in a solvent such as benzene (which is done with decaf coffee), filter it and then extract the solvent for reuse. This would in effect sterilize and remove any bacteria and most likely alter any enzymes that would be sensitive to heat.
If the gum is a raw import grade and not processesed for food, Art's method certainly makes sense. For a food grade gum, it would depend on what previous cleaning process was employed.
An interesting idea nonetheless.
Dick Sullivan
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