Re: Nonvolatile gelatin hardener

Ryuji,
Looks like something interesting. Thanks for detailed posting of the
procedure. How would you compare the properties of gelatine hardened by
epox with traditional chrome alum hardening.

Marek Matusz

> I've tried bisepoxide compounds to harden gelatin. As I anticipated
> from molecular structures and chemical properties of epoxides, they
> react much more slowly than glutaraldehyde (glut). My preferred
> compound for this purpose was diglycidyl ether of glycerol
> (epox). There are several other diglycidyl or polyglycidyl ethers of
> glycols and similar substrates, which can be useful. A 2 to 10% of dry
> gelatin weight is a good starting point for the hardener dose.
>
> Example
>
> In a 1000 ml of water at 25C, 30g of ossein gelatin of 230 Bloom
> strength was soaked with slow agitation until fully swollen. The
> mixture was heated to 40C with continuous agitation. The temperature
> and agitation were maintained until the gelatin was completely
> "dissolved" with water to form a single phase. A 0.06 ml of a
> surfactant (a blend of secondary alcohol ethoxylates) and 0.1g of
> sodium salt of 2-phenylphenol (bactericide and fungicide) were added
> thereto, and the mixture was set aside until use.
>
> A 100ml portion of the premade sizing solution was taken, heated to
> 40C and 0.1ml epox was mixed thereto, followed by a vigorous agitation
> until the epox was completely mixed into the aquaous gelatin
> phase. The mixture was maintained between 35 and 40C while applied to
> the surface of Strathmore Bristol 300 series smooth vellum (260gsm)
> with a brush twice, without drying, with diagonal strokes.
>
> Comparison mixture was made with same gelatin solution except glut was
> used instead of epox.
>
> Glut can smell if the ventilation of the room is inadequate. Epox
> doesn't smell.
>
> Epox hardened solution is a bit easier to coat with brush because it
> is significantly less viscous. (Viscosity of epox hardened gelatin
> solution is almost unchanged from plain gelatin solution.) Epox
> hardened solution is virtually free of foaming because epox serves as
> a defoaming agent as well. If too much epox is added, the excess epox
> simply won't get blended with the water phase and it makes a separate
> phase.
>
> Gelatin hardened with glut is easier to gel when cooled. Gelation of
> epox hardened solution is probably about the same as the original
> (unhardened) gelatin solution.
>
> Glut hardened paper is usable when the paper is completely dry. On the
> other hand, epox hardened paper is still almost unhardened by that
> time. By day 2, gelatin is significantly hardened but it is not
> hardened enough to use for silver gelatin emulsion (coated warm). By
> day 3, the gel is hardened enough, but the best result is obtained a
> week after sizing the paper.
>
> Hardening property of epox can be increased by increasing gelatin
> concentration, epox concentration, or both. Unless impractically large
> amounts of them are used, they do not cause immediate hardening to
> make stiff solid that doesn't dissolve again. (With glut, it's easy to
> cause the gelatin to solidify like that to ruin the brush if excessive
> amount of glut is used.)
>
> Hardening property of epox decreased when gelatin of smaller molecular
> weight was used. Users of food gelatin might want to use a bit higher
> amount of gelatin, epox, or probably both (e.g. 4% gelatin, 0.3% epox
> in water). But more stronger paper surface can be obtained with high
> quality ossein gelatin of large avg molecular weight.
>
>
> Advantage:
>
> 1. it gives off little or no fume (and no smell)
> 2. it does not ruin the brush when too much hardener is added
> 3. it also serves as a defoaming agent in aquaous solution of gelatin
> 4. it does not immediately increase the viscosity of gelatin solution
> 5. it does not immediately lower the gelling temperature of gelatin
> 6. gelatin hardened with it swells just as much as glut-hardened gel
> 7. it hardens gelatin as well as many nongelatin polymers having
> reactive carboxyl or amino groups (yes this reacts with both these
> and probably more)
>
> Disadvantage:
>
> 1. it hardens gelatin very slowly (gel isn't hardened when just dried)
> 2. it is more expensive than glut (so what?)
> 3. it is harder to buy than glut (but it is commercially available)
>
>
> MSDS and other info indicates that this compound is not terribly
> dangerous, and safety devices recommended in MSDS are totally within
> the reach of this community. But I strongly recommend to review MSDS
> before using any new chemical.
>
> Finally, please don't ask me where you can buy this chemical. It is
> commercially produced at least by a couple of chemical companies in
> Japan, and it is found in the catalogues of chemical dealers. I think
> companies like B&S and Photographer's Formulary should be carrying
> this chemical, and you should call them to show that there is market
> interest. A small bottle (say 50ml) can go a very long way as you see
> above.
>
> PS. This Strathmore Bristol vellum paper is quite absorbent and takes
> wet processing well, but this paper doesn't dry very flat, at least
> after silver gelatin emulsion is coated on the sized paper, processed,
> and dried. This vellum is cheap but I like Artistico Extra White
> better for anything of value.
>
Received on Fri Aug 5 12:24:01 2005