Re: gum arabic

[Jack Brubaker <jack@jackbrubaker.com>]

There is no comment here about the original watercolor image having changed color. It is just the inappropriate use of gum as a varnish that has failed. There are many examples of gum being used as a binder going back much further without failure. Generally the only concern with really old watercolor painting is the viability of the pigments used at the time.

Jack

2009/1/30 Loris Medici <mail@loris.medici.name>

Maybe, but they're also talking about darkening (cracking is another
issue) and that's my actual concern -> can it happen to hardened gum also?

Anyway, we know that gum prints are stable for at least 120 - 130 years
(by looking to the condition of actual prints made in the late 19th
century), which is fine. But the image on the page is around 2-2.5 times
older than the oldest gum dichromate print we can inspect...

Regards,
Loris.


30 Ocak 2009, Cuma, 10:57 pm tarihinde, Katharine Thayer yazmış:

>> Loris wrote:
>>
>> I'm not that much confident since I had read this:
>> http://www.history.org/foundation/journal/Winter01-02/bird.cfm
>>
>> What do you (all) think?
>
> Loris, I think it's unfortunate that they used unhardened gum as a
> varnish; soluble gum is extremely likely to crack, as it did in that
> instance, as well as being totally water soluble.  (In this case the
> water solubility was a blessing, because it made it easy to
> remove).   This isn't relevant to our use of gum arabic where the gum
> that remains in the artwork is not water soluble and doesn't have the
> same properties of being susceptible to cracking, so I'd say you
> shouldn't let that account shake your confidence in the archivality
> of a gum print.
> Katharine