RE: Gelatin-polymer blend (was Re: Gesso sizing)

A couple of questions related to sizing:

Why the addition of gelatine to acrylic is necessary? Can't one use direcly
diluted acrylic medium? What about polyurethanes (such as clear glossy wood
finishers)?

If gum has adhesion problems with pure acrylic (I don't know if it's really
so; I'm just speculating in order to get more info...) then wouldn't acrylic
cause flaking/grainness?

BTW, IIRC Getty Museum is running acrylic longevity tests... I guess we'll
have much more info about this issue soon.

TIA,
Loris.

-----Original Message-----
From: Marek Matusz [mailto:marekmatusz@hotmail.com]
Sent: 21 Ocak 2006 Cumartesi 18:33
To: alt-photo-process-l@sask.usask.ca
Subject: Re: Gelatin-polymer blend (was Re: Gesso sizing)

Katharine,
I have used acrylic medium (20% in a 6% gelatine). Medium dies notcontain
any pigment, no reason to worry about titabium dioxide bleaching. Inded very
durble sieze for gum.
Marek, Houston

>From: Katharine Thayer <kthayer@pacifier.com>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: alt-photo-process-l@sask.usask.ca
>Subject: Re: Gelatin-polymer blend (was Re: Gesso sizing)
>Date: Fri, 20 Jan 2006 06:48:32 -0800
>
>What's the difference between transparent acrylic gesso and acrylic
>medium?
>
>I did try mixing gelatin and acrylic medium once and wasn't happy with
>the results, but it was only that one try. As I recall, the image
>broke up and flaked off, which suggests maybe I put too much acrylic in
it.
>
>One of the reasons I haven't used the gelatin-gesso size for
>exhibition prints is that I've never been sure about the permanence of
this
>combination, although it is my favorite surface to print on. Ryuji's
>cautions about the titanium dioxide do give me pause. Perhaps someone
>who lives where the sun actually shines could size some paper with
>this combination, print a gum print on it, and put it in ta
>south-facing window for a few weeks and see what happens.
>
>kt
>
>
>On Jan 19, 2006, at 8:35 PM, Gordon J. Holtslander wrote:
>
>>
>>The liquitex is labelled:
>>
>>Liquitex Acrylic Gesso Transparent
>>has the number 7604 on the bottle
>>
>>label states
>>
>>"Flexible clear acrylic gesso for acrylic oil pastel and more"
>>
>>The white glue is
>>
>>Weldbond Universal Adhesive
>>
>>My foam roller was bought from the local Coop hardware store (my
>>favourite photo supply store :) )
>>
>>Its a finishing roller a foam roller about 7 inches long 1 inch
>>diameter with a very fine nap.
>>
>>I charge it by pouring the gelatin mix in a narrow tray just larger
>>than the roller.
>>
>>I clean these just by rolling rinsing and squeezing out moisture.
>>
>>I often get fine bubbles from the roller - I will often wipe with a
>>finish paint "pad" that has the same fine nap as the roller.
>>
>>I'm not claiming to get spectacular results. Just haven't been happy
>>with the way I sized in the past - often got crappy sizing. Trying to
>>see if there are easier quicker better ways to size.
>>
>>Will try casein (and maybe casien -weldbond) for sizing too.
>>
>>Gord
>>
>>
>>On Thu, 19 Jan 2006, Judy Seigel wrote:
>>
>>
>>>
>>>On Thu, 19 Jan 2006, Gordon J. Holtslander wrote:
>>>
>>>
>>>>Liquitex make a clear acrylic gesso - I assume (bad practive) that
>>>>is has no titanium whitener.
>>>>
>>>
>>>Definitions change over time -- I remember when a "dork" was a jerk,
>>>which is to say a nudnik, and now it seems it's an expert, geek or
>>>techie.
>>>So I say with some reservations that by definition *traditionally* a
>>>gesso
>>>had to have a whiting substance in it. To quote Mayer: It's made by
>>>mixing
>>>"an inert white pigment such as chalk, whiting or slaked plaster of
>>>Paris
>>>with an aqueous binder such as a solution of glue, gelatin or casein."
>>>
>>>I don't think by the way that gesso has titanium -- Mayer has a section
>>>on
>>>"Defects of Gesso panels" which I haven't read for 105 years, but my
>>>recollection is that they would be some kind of cracking, which
>>>presumably
>>>(better word than "assume," n'est-ce pas?) would be obviated by the
>>>gelatin.
>>>
>>>When I learned to make gesso, 103 years ago, we slaked plaster of
>>>Paris...
>>>and somewhere along the line I was told that *rotten* plaster made the
>>>best gesso, that is, you slake then keep a year or so til it rots. I
>>>made
>>>some up and worked off it for a long time -- I haven't used the gelatin
>>>gesso mix for a while (Bernie Boudreau's version is cited in P-F #6),
>>>because for my printing, plain Knox hardened in glyoxal or formaldehyde
>>>proved easiest & best. But I still have a couple of inches of the rotten
>>>plaster in a gallon container.
>>>
>>>That's the beauty of rotten plaster -- it keeps !
>>>
>>>PS. Gord: Does Liquitex call that clear stuff "gesso", or ...? Is
>>>"white
>>>blue" a misprint for "white glue"... or... ? (Elmers, maybe?) How do
>>>you
>>>clean the foam roller? Any special kind of foam?
>>>
>>>TIA,
>>>
>>>Judy
>>>
>>>
>>>
>>>>
>>>>I have been playing around with sizing techniques.
>>>>
>>>>Did a mix of gelatin (250 ml) and a little (20 ml) white blue, hardened
>>>>with chrome alum, rolled on with a foam roller. Seemed to give a much
>>>>smoother/cleaner surface than plain gelatin. But then the gelation
>>>>coat
>>>>may simply have been poorly coated.
>>>>
>>>>Gord
>>>>
>>>>On Thu, 19 Jan 2006, Ryuji Suzuki wrote:
>>>>
>>>>
>>>>
>>>>>I've tried gesso mix but one objection I had was that the acrylic
>>>>>gesso is gritty because of matting agents in the mix. Another
>>>>>objection I found is that the gesso contained titanium white and other
>>>>>things I would not want to have in my prints unless archivality is
>>>>>proven in the particular combination. Titanium white is very
>>>>>photoactive and generates a lot of radical chain reaction in the
>>>>>material when exposed to UV, and this was the main cause of problems
>>>>>in early days of RC papers. Photographic industry learned enough and
>>>>>today's products have good amount of means to prevent the problem, but
>>>>>I am not sure of gesso in sizing layer.
>>>>>
>>>>>
>>>>
>>>>---------------------------------------------------------
>>>>Gordon J. Holtslander Dept. of Biology
>>>>holtsg@duke.usask.ca 112 Science Place
>>>>http://duke.usask.ca/~holtsg University of Saskatchewan
>>>>Tel (306) 966-4433 Saskatoon, Saskatchewan
>>>>Fax (306) 966-4461 Canada S7N 5E2
>>>>---------------------------------------------------------
>>>>
>>>>
>>>>
>>>
>>>
>>
>>---------------------------------------------------------
>>Gordon J. Holtslander Dept. of Biology
>>holtsg@duke.usask.ca 112 Science Place
>>http://duke.usask.ca/~holtsg University of Saskatchewan
>>Tel (306) 966-4433 Saskatoon, Saskatchewan
>>Fax (306) 966-4461 Canada S7N 5E2
>>---------------------------------------------------------
>>
>
Received on Sat Jan 21 15:59:30 2006