RE: archivalness of gum

[Dave S <fotodave@dsoemarko.us>]

oh, now I remember we had a discussion on this years ago. I think it was I
who asked exactly the same question, and you were the one who gave the
answer too. 

I am getting old.   :-)


Dave  

> -----Original Message-----
> From: Ryuji Suzuki [mailto:rs@silvergrain.org] 
> Sent: Friday, December 21, 2007 1:51 PM
> To: alt-photo-process-l@usask.ca
> Subject: Re: archivalness of gum
> 
> From: Dave S <fotodave@dsoemarko.us>
> Subject: RE: archivalness of gum
> Date: Fri, 21 Dec 2007 11:04:09 -0500
> 
> > Ok, mybe in a less technical sense, does hardening reduce 
> or minimize 
> > the problem with bugs?
> 
> No.
> 
> > I have always thought (though I have no scientific proof and didn't 
> > check) that the hardened gelatin would capture less water from the 
> > atmosphere and so would preserve better... sort of like a 
> jello would 
> > certainly spoil faster than the dry gelatin powder. Is this 
> not true?
> 
> Hardener only suppresses swelling of gelatin when the gelatin 
> is soaking wet or half wet. Once dried, the ability of 
> gelatin to exchange moisture with air is mostly determined by 
> the air temperature, humidity and the plasticizers used in 
> the gelatin coating, if any. Hardener has little or no 
> influence on this.
> 
> Also, hardener molecules are tightly bound to the host 
> macromolecules and not really free to act as biocide as you 
> would expect from free aldehydes.
> 
> If you want to protect gelatin from fungi you should use 
> suitable humidity control. A RH of 30% is very good.
> 
> Another approach may be to use a fungicide treatment of the 
> image. I was asked by several people to offer such a product 
> (Tetenal made a final rinse solution containing a biocide, for
> example) but I was reluctant to do so. Fungicide may prevent 
> fungus but high humidity is not a desirable condition for the 
> image permanence even if fungus problem does not occur. 
> Humidity control, while potentially expensive depending on 
> the region, is the best overall solution.
> 
> --
> Ryuji Suzuki
> "Patriotism is the last refuge to which a scoundrel clings."
> (Bob Dylan, Sweetheart Like You, 1983)
> 
>