Gelatine - Borax - Formaldehyde

Thanks for the info Ryuji... Probably you missed my other question to you:

Few days ago I asked "How much borax I should add to water in order to make
formaldehyde work faster?" becase you said formaldehyde works faster when PH
is over 8... The web resouces I managed to find (mostly detergent-related)
say PH of borax is the same (9.2) regardless of soln. strength, and other
resources say borax water solubility is around 51gr per 1000ml (at 20C).

I plan to size paper with this procedure:

Will take 100ml of distilled water (20 - 24C), then will add 3gr of gelatine
and wait about 20 mins. Later, I will put the gelatine soln. container in a
hot water bath (50C) and wait until the soln. temperature raise to about 40
- 50C. Then I will stir to make the gelatine soln. Homogeneous. After that,
I will add 1gr. of borax and stir again and lastly I will add 1.5ml of
formaldehyde and stir again. Finally I will start to coat paper by dipping a
brush to the sizing soln. and brushing it on the paper.

Do you (and others) think it will work this way? This is not a gum-only
related question. I also plan to prime glass this way for making cyanotypes
on glass (three coats; first two being hardened gelatine, last one being 1+1
unhardened gelatine + cyanotype emulsion).

TIA,
Loris.

-----Original Message-----
From: Ryuji Suzuki [mailto:rs@silvergrain.org]
Sent: 22 Ocak 2006 Pazar 00:26
To: alt-photo-process-l@sask.usask.ca
Subject: Re: Gelatin-polymer blend

From: Loris Medici <mail@loris.medici.name>
Subject: RE: Gelatin-polymer blend (was Re: Gesso sizing)
Date: Sat, 21 Jan 2006 23:59:02 +0200

> Why the addition of gelatine to acrylic is necessary? Can't one use
> direcly diluted acrylic medium?

That's because adhesion will be very poor. Even when gelatin is blended, if
the fraction of acrylic polymer is too high, the adhesion suffers, even with
gelatin emulsions, which generally has excellent adhesion compared to other
binder systems.

The basic strategy in multilayer coating is that, you want to make small
stepwise change in hydrophilicity and swelling from one layer to the next.
For example, in the case of sheet films, the base is polyester, which is
hydrophobic and nonswelling. The first layer of subbing is weakly
hydrophilic and weakly swelling, like latex polymers. The next layer will be
more hydrophillic and more swelling, and so on. You don't want an abrupt
change between adjacent layers; damage due to mechanical distortion is a lot
more likely when the material is wet and swollen. This can be emulsion
flaking off, reticulation, or other forms of mechanical damage.

Gum is very hydrophilic. So the layer under gum shouldn't be very
hydrophobic. Straight acrylic medium is a poor choice for this reason.

> BTW, IIRC Getty Museum is running acrylic longevity tests... I guess
> we'll have much more info about this issue soon.

Archival property of acrylic medium with pigments is a different story from
using it as a part of photographic material, though. I'm less worried about
acrylic medium itself, but I am very leery of accepting titanium white as a
part of sizing layer without doing extensive tests. Exactly what AGFA,
Ilford, Kodak, Fuji, Mitsubishi and Konica did to remedy this problem is not
widely known. For this matter, I don't even trust RC papers made in eastern
European countries. (Their baryta papers are generally fine, though.)
Received on Sat Jan 21 17:24:13 2006