[alt-photo] Re: I know, another sizing question

[henk thijs]

Trevor,
Loris mentioned 'brittle', and yes he is right, maybe you were lucky :-)
The rabbitskin glue must be handled more or less like gelatine : heat it until 60 degree C, and than go down to 40 when coating.
If you apply the 60 degree stuff , you will have a problem later on. Oh yes, just experience.
By the way, be sure you buy the rabbitSKIN and not the 'general skin/bone glue' without mentioning 'rabbit', i bought once the stuff looking like small pearls , and they told me it was 'nearly' the same as the rabbit-skin stuff. It wasn't , not for gum, and not for inkjet printing.
BOESNER in germany  sell rabbitskin glue as 'technical gelatine' , whatever that means.
cheers,
Henk

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www.thijs-foto.com
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On 10 sep 2010, at 18:12, Trevor Cunningham wrote:

> 
> I just coated some paper with the rabbit skin glue and it it produces a nice silky smooth surface...hopefully the gum doesn't slide off. I know someone said it's brittle, but it soaked right into the paper. If it's not consistent this time, I might try diluting the solution a little and go from there.
> 
> Thanks for all the input gang. I'm just happy to have chemicals, but it's the other little things and living in strange places that make me wish I was more of a MacGuyver...thought I feel more like a MacGruber (if anyone follows SNL anymore)
> 
> On 9/10/10 5:50 PM, Peter Friedrichsen wrote:
>> My results with Elmers PVAc have been unsuccessful since,as Loris points out, it will not resist water and will fail as a size.
>> 
>> I did some digging some time ago (an earlier post) and found that the Gamblin PVAc is a chemically modified beast that greatly improves water resistance of standard PVAc, so it works. Trial and error runs from paint/hardware store products may eventually yield success as Loris has found, but even if you luck upon the right PVAc type, you still have to deal with the unknowns of the ageing of a sizing from a product with unknown composition and pH.
>> 
>> Re Casein as size
>> 
>> I haven't used it as a size but I do know it will form a  very water resistant coating once hardened with Glyoxal or Formaldehyde. These hardened films are a little more brittle than gelatin films, and the films forma mat finish with may provide more tooth good or bad.
>> 
>> I think if you had a source of sodium caseinate powder, then it may be worth experimenting, but to precipitate the casein from skim milk every time you need to size would be more effort than it is worth unless there were some clear advantages in terms of performance or convenience. The only clear advantage I can see off the top is that the caseinate solution is liquid at room temperature and avoids the warming step of gelatin sizing.
>> 
>> Re whey
>> 
>> As was mentioned, the whey (clear solution) that is left over after the casein is filtered out also contains hardenable protein but it is mixed with lots of lactose and other impurities. I know you can purchase purified whey protein isolate which is used in foodstuffs and as a body building powder. From what I understand it suffers from poor adhesion and forms a film that is brittle and flaky but I have never tried this as a sizing.  It does have the advantage that it is very soluble in water and you can make 50% solutions without too much viscosity.-kind of like gum arabic in this regard.
>> 
>> Peter Friedrichsen
>> 
>> At 06:14 AM 09/10/2010, you wrote:
>>> If I'm not mistaking, Elmer's glue was used in place of gum or something - that means it isn't waterproof; something good for a gum replacement, but not good for being able to used as a sizing... As I said before, you should look for something that is PVAc based, clear (when dried as a film) and waterproof. See hardware / paint stores, I buy mine from a paint store, dilute it 1+4 and use - paper's ready when dry, and the sizing is very robust; I had a student put 9 layers w/o any staining... Regards, Loris. 2010/9/10 Trevor Cunningham <trevor at chalkjockeys.com>: > Â Maybe not? I read in the manufacturer's details that it has a pH of 4.7...I > know the Gamblin product (which I can't get) is pH neutral. Would diluting > the glue with distilled water help to raise this number a little? Mix a > little baking soda into the solution? > > On 9/10/10 9:25 AM, Trevor Cunningham wrote: >> >> Â Is good old fashioned Elmer's school glue a suitable PVA glue? That I can >> find. _______________________________________________ Alt-photo-process-list | http://altphotolist.org/listinfo
>> 
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