From: Sandy King (sanking@clemson.edu)
Date: 04/13/02-08:47:02 AM Z
Judy Seigel wrote:
>
>
>Sandy, would you please explain why you mist with alcohol, not just with
>water ? I've noticed these specks from time to time, but am pretty sure
>they disappear as the size ages, definitely as you coat with a gum layer
>and expose .... or maybe you just don't notice them any more. I don't see
>them as a real problem, but you pique my curiosity -- is there some reason
>the alcohol kills them & a plain water mist wouldn't?
Judy,
Frankly, I never tried misting with water. I just rather assumed that
it would not dissipate the bubbles as effectively as alcohol. The
idea to mist with alcohol came out of my experience in adding a bit
of it to the pigmented gelatin in making carbon tissue. When I saw
how effective misting was for sizing papers I tried it with the
tissue itself and it is very effective for that also.
>I remember by the way some years ago Terry King saying that you had to
>totally dissolve the gelatin in hot water with a longish soak -- to avoid
>those shiny specks. I tried that & found it didn't make the slightest bit
>of difference.
By habit in preparing gelatin I first leave the gelatin in cold water
for about 30 minutes, then soak in warm water (at about 120F) until
the gelatin dissolves. This generally takes about 30 minutes.
>
>> If the problem is due to the crystalline faces of the gelatin
>> microcrystals a solution might be to add some starch to the gelatin
>> solution to give a more matte surface.
>
>That sounds like an interesting variation... Have you done it? How much
>"starch" would you add? Without pre-cooking? Cornstarch?
>
My theory about the specks is that they are caused by small air
bubbles that erupt and leave minute spots on the paper unsized, not
to the "crystalline faces" of the gelatin. As far as I know gelatin
does not have a crystalline form.
As for the question about starch, yes I have used it a lot in sizing
art papers for double transfer carbon work where the paper will
subsequently be soaked only in cool water. I use regular corn starch,
about 10-20g per liter of sizing solution. I add the starch directly
to the warm gelatin solution just before sizing, with no cooking.
Sandy
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