[alt-photo] Re: evaporation of gum mixture

[Tomas Sobota]

I have never used prepared gum solution. I prepare gum in the original
artisanal way, dissolving gum arabic stones in water. Then, I keep the
solution in dark glass bottles, well stopped and preserved with a few thymol
crystals. Kept in this way, I have never observed any evaporation, not even
in a time span of years. So, what is being described is strange, and
probably related to the way that the commercial gum is prepared or
preserved.

I understand that buying prepared gum is easier and somewhat faster, but it
is surely more expensive and you never know with any certainty what is in
there. Preparing gum from bulk gum arabic stones is so easy, that I wonder
why it is not done more often, at least on the other side of the ocean ...

Tom Sobota
Madrid, Spain

On Sat, Jul 3, 2010 at 3:18 AM, Katharine Thayer <kthayer at pacifier.com>wrote:

> Okay, that sounds like the standard DS gum, not the premium; I have no
> experience with that.
>
>
>
> On Jul 2, 2010, at 5:05 PM, Paul Viapiano wrote:
>
>  Cool, thanks Katherine...
>>
>> The Formulary gum is very light colored, and that's what I've used since
>> day one. I got the DS gum on sale, great price and it is definitely a darker
>> maple syrup color. Haven't used it yet...
>>
>> p
>>
>>
>>
>> ----- Original Message ----- From: "Katharine Thayer" <
>> kthayer at pacifier.com>
>> To: "The alternative photographic processes mailing list" <
>> alt-photo-process-list at lists.altphotolist.org>
>> Sent: Friday, July 02, 2010 2:42 PM
>> Subject: [alt-photo] Re: evaporation of gum mixture
>>
>>
>>
>>  Hmm, that's interesting.  I know nothing about what Formulary is  selling
>>> for gum now, since I quit buying gum from them when they  switched from a
>>> gum I really loved to a dark gummy gum for their  premium gum and continued
>>> charging a premium price for it.  That was  some years back, and as I said,
>>> I know nothing of their present gum.   The only gum I've seen this happen
>>> with is Daniel Smith premium gum,  and it's been a continuing problem with
>>> DS gum since I started using  it 3-4 years ago.  Exact same containers  that
>>> I've always kept my  gum-pigment mix in, but with other gums I've never had
>>> this  evaporation problem.  With the Daniel Smith gum it's so pronounced
>>>  that  the mixes have become  more viscous within a short time and  dried
>>> out altogether within a few months, so I've had to throw out  the mixes,
>>> which is very annoying because it's extremely wasteful of  pigment.  In the
>>> beginning,  I thought it was because the workshop in  which I was doing gum
>>>  at the time  I switched to Daniel Smith had a  bank of west-facing windows
>>> that didn't open, and it got very hot in  there on summer afternoons.  But
>>> the problem continued unchanged when  I moved to my present digs, where the
>>> gum workroom is in a cool basement, so I'm convinced it's the gum (and
>>> besides, mixes made with other gums and stored in the same containers
>>> survived that hot  workroom quite well and remain  fresh and nicely pourable
>>> to this day).
>>>
>>> Whether you can reverse the problem by adding water is  a good  question;
>>> in my case,  by the time I noticed the increased  viscosity, it was too
>>> late; adding water usually wasn't a  satisfactory solution because the mix
>>> had gotten gummier and the  water didn't mix in well.   But if you catch it
>>> fast enough, as  you're doing by measuring the loss, it seems as if it
>>> should work.
>>>
>>> Hope any of that is helpful,
>>> katharine
>>>
>>>
>>>
>>>
>>> On Jul 2, 2010, at 1:00 PM, Paul Viapiano wrote:
>>>
>>>
>>>  Formulary, til present.
>>>>
>>>> Then, will switch to DS.
>>>>
>>>> p
>>>>
>>>> ----- Original Message ----- From: "Katharine Thayer" <
>>>> kthayer at pacifier.com>
>>>> To: "The alternative photographic processes mailing list" <alt-
>>>> photo-process-list at lists.altphotolist.org>
>>>> Sent: Friday, July 02, 2010 12:54 PM
>>>> Subject: [alt-photo] Re: evaporation of gum mixture
>>>>
>>>>
>>>>
>>>>
>>>>  Paul, what gum are you using?
>>>>>
>>>>>
>>>>> On Jul 2, 2010, at 11:51 AM, Paul Viapiano wrote:
>>>>>
>>>>>
>>>>>
>>>>>  Hello all...
>>>>>>
>>>>>> Having traced my pt/pd to a highly alkaline batch of Fabriano ,  I
>>>>>> have another question on an entirely different subject.
>>>>>>
>>>>>> Sometimes I make these little premixtures of watercolor pigment  and
>>>>>> gum arabic, nice and handy for printing tricolors in the  same pigments. I
>>>>>> mix about 1 gram pigment to 9 ml of gum.
>>>>>>
>>>>>> In May, I made a mixture and weighed it at 17.9 grams in its   plastic
>>>>>> snap-cap container. Two months later, it weighs in at  17.2  grams. What is
>>>>>> it that is evaporating? Gum arabic? I'm  curious...
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>>>>>>
>>>>>>
>>>>>>
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