Diluting gelatin with alcohols

Simon Moore <couteaufin [at] aol__com> writes

>Cheryl Jackson <cheryl.jackson [at] naa__gov__au> writes
>
>>I have been trying to dilute a 10% W/V aqueous solution of gelatine
>>with ethanol or isopropyl alcohol (down to 2%) without success. It
>>keeps turning stringy and opaque.
>>
>>Should I be using a different grade of gelatine?
>>
>>The solution will be used to consolidate a flaking gelatine emulsion
>>back down onto its glass plate.
>
>The problem of using alcohol with gelatine is that the protein
>chains are coagulated by the alcohol, hence the white strings.  Just
>hydrate the gelatin in a little warm water, if it's too viscous you
>can dilute it further by adding more warm water.  It is difficult to
>'thicken up' if too dilute and constant re-heating damages the long
>molecular chains in the gelatine.  Use leaf gelatine rather than
>powder, it has better adhesion for some reason. If you do this type
>of work regularly it is worth making up a batch of hydrated gelatin
>by adding 1 ml of glacial acetic acid in the gelatine mix and 2ml of
>glycerol (per 100 ml) to your hydrated leaves of gelatine. ...

I just notice that glacial acetic acid is mentioned here, and
thought a reminder about how to store it might be in order.  I
inspect many labs that don't know that it needs to be stored all by
itself.  It is both flammable and highly corrosive.  It will react
with solvents and many other acids.  Of course, if you buy it more
dilute, say 50%, those extreme properties go away and it can go in
with the other acids.

Monona Rossol
Arts, Crafts and Theater Safety
181 Thompson St., #23
NYC NY 10012-212-777-0062


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                  Conservation DistList Instance 26:6
                   Distributed: Monday, July 2, 2012
                        Message Id: cdl-26-6-002
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