U of S | Mailing List Archive | alt-photo-process-l | Re: gum arabic

Re: gum arabic

Can anyone explain what a user might notice if she was using a poorer
quality gum?  In the experience of the users, how does the pedigree pf
the gum affect the print or the process of printing?

On Sat, Jan 17, 2009 at 11:56 AM, Katharine Thayer <kthayer@pacifier.com> wrote:
> P.S. The term "gum arabic" is used rather loosely, sometimes to refer to
> acacia senegal, sometimes to gum acacia of any variety, and sometimes even
> to other species, so I wouldn't put too much faith in the term "gum arabic"
>  as being synonymous with acacia senegal.
> kt
> On Jan 17, 2009, at 9:18 AM, Alberto Novo wrote:
>>> Also, sort is important;  the kordofan, labeled (1)  will be a higher
>>> (finer) sort than the other, at sort 3.  Hope that's  helpful,
>>> Katharine
>> As for Kremer's gum arabic, their pdf on their gum details is the same for
>> the three qualities, though their prices are different, so I am wondering
>> what they really are. I am not buying from Kremer, because I have about 1 kg
>> of gum arabic of unknown origin since a long time (though it works well).
>> About Acacia senegal (cited from Kremer pdf):
>> "Gum Arabic is a dried exudate obtained from the stems and branches of
>> Acacia senegal (L.) Willdenow or closely related species of Acacia (fam.
>> Leguminosae). A. seyal is a closely related species. Gum arabic consists
>> mainly of high-molecular weight polysaccharides and their calcium,
>> magnesium, and potassium salts, which on hydrolysis yield arabinose,
>> galactose, rhamnose, and glucuronic acid. Items of commerce may contain
>> extraneous materials such as sand and pieces of bark which must be removed
>> before use in food. Gum arabic from A. seyal is sometimes referred to as gum
>> talha."
>> "Gum Arabic from A. senegal is a pale white to orange-brown solid, which
>> breaks with a glassy fracture. The best grades are in the form of whole,
>> spheroidal tears of varying size with a matte surface texture. When ground,
>> the pieces are paler and have a glassy appearance. Gum from other acacia
>> species may not have the characteristic tear shape and are often darker in
>> colour. Gum from A. seyal is more brittle than the hard tears of A.
>> senegal."
>> One among the differencies (not easily testable at home) is their optical
>> properties: water solutions from A. senegal are levorotatory, from A. are
>> dextrorotatory.
>> Alberto