Re: polivinyl alcohol vs. gelatin sizing

From: Jack Brubaker ^lt;[email protected]>
Date: 07/31/05-02:10:37 PM Z
Message-id: <BF129A6D.12984%jack@jackbrubaker.com>

Ryuji,

The dilute mix of acrylic and water will grow mold. I add a very small
amount of household ammonia to my dilute acrylic size and it keeps for years
(without refrigeration). Do you see any harm in using ammonia? Can you
suggest any other household chemical that might work better in your
technical judgment?

Jack

> From: Ryuji Suzuki <rs@silvergrain.org>
> Reply-To: alt-photo-process-l@skyway.usask.ca
> Date: Sat, 30 Jul 2005 11:45:38 -0400 (EDT)
> To: alt-photo-process-l@skyway.usask.ca
> Subject: Re: polivinyl alcohol vs. gelatin sizing
>
> From: Katharine Thayer <kthayer@pacifier.com>
> Subject: Re: polivinyl alcohol vs. gelatin sizing
> Date: Sat, 30 Jul 2005 08:04:34 +0000
>
>> I don't understand your answer to my question about why one would use
>> PVA rather than acrylic medium. It's true that polyvinyl alcohol would
>> require a hardener, but that would be a reason to use acrylic, not a
>> reason to use PVA. And so on. So maybe my question wasn't clear; I
>> still don't understand why PVA rather than acrylic.
>
> Acrylic medium uses poly(vinyl alcohol-co-acetate) as the emulsifying
> agent to hold polyacrylates like poly(alkyl methacrylate). This way,
> in effect, much of the wet content being coated is actually a
> copolymer of vinyl acetate and vinyl alcohol and water. I think these
> polymers are better used in a small amount as an additive to gelatin.
>
> In response to Giovann's post, I think gelatin is a lot easier to coat
> as long as it is at the right temperature. Also, PVOH and acrylic
> media are also susceptible to bacterial attack and products contain
> biocides.
Received on Sun Jul 31 14:09:56 2005

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