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  #11  
Old 24-08-04, 12:40 AM
Michael Brown
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Default boiled water for R.S.G.

Hi Real Gesso,
I'll give it a try using a cooking themometer. I'll also check to see what temperature the boiled water is after it has been poured into the thick pyrex measuring cup. Can you describe the nature of failed gesso, I've never experienced any problems with adhesion. Thanks.
Michael
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  #12  
Old 24-08-04, 02:41 PM
realgesso realgesso is offline
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Quote:
Can you describe the nature of failed gesso, I've never experienced any problems....
The most obvious indication that the glue has gone south is that you will notice the surface to be shiney in places and also areas that have a pinkish tint to them. The less obvious requires a device that tests coating adhesion, basically it's a device that you use by glueing a disk of a pre-determined size to the surface to be tested, this disk has a stem that attaches to a hydrualic pulling mechanism similar to a bearing puller, the pulling device has a dail guage that tells you how many p.s.i. it takes before the coating fails, that is, seperates from the substrate.

p.s. Try a glass candy thermometer, they're pretty accurate.
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  #13  
Old 24-08-04, 08:18 PM
Michael Brown
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Default gesso defects due to overheated r.s.g.

Thanks real,
I imagine you must have considerable experience with problems resulting from faulty gesso, as your panals are subjected to the stress of shipping and handling that the average E.T. painter would not encounter (especially with the number of panals involved). Can you submit a link to your site, or a mailing address that forum members could access? Thanks again.

Michael
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  #14  
Old 24-08-04, 11:00 PM
realgesso realgesso is offline
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Sure, it's also my signature at the bottom of my posts...
http://www.realgesso.com/
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  #15  
Old 21-01-05, 12:06 AM
giannetti
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Default Gesso pva, rsg, egg tempra help

i have a bottle of gamblin pva which i was going to use instead of a acrylic gesso
Reason: i do egg base tempera and it is strongly recommend not to use a acrylic gesso what do you think?
i cant use rsg because of the smell i'm an old asthmatic
any suggestions
some one did rsg gesso for me for years but can't any more

any suggestions ?????
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  #16  
Old 21-01-05, 01:05 AM
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DLH DLH is offline
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Gamblinís assertion of the superiority of PVA is probably true, But it applies only to oil on canvas. RSG is traditionally used on raw canvas to prevent the absorption of oil which causes the canvas to rot. The problem is as Gamblin states, moisture is continually and destructively exchanged from the back of the painting. PVA, in this application should be superior to RSG. Being more flexible, it does a better job of keeping out the oil, and being less hydroscopic, it slows environmental moisture transfer. Once again this applies only to oil on canvas. There is really no substitute for animal glue in gesso.

Why not buy preprepared panels from realgesso? (see member list). Art Supply Wearhouse has traditional gesso panels also.
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  #17  
Old 21-01-05, 05:33 AM
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DLH DLH is offline
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There is really no substitute for animal glue in gesso.
I apologize. How dare I make such a categorical statement with no evidence. My rant was really in response to postings earlier in this thread.

A feature we prize in our gesso is the way it absorbs water. This is due to the high stone dust to binder (glue) ratio. Perhaps if PVA is thinned enough it might work as a gesso binder. Anyway, I mixed some up tonight, and while I was at it, I made a batch with acrylic medium. Iíll report my findings.
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  #18  
Old 21-01-05, 02:21 PM
realgesso realgesso is offline
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How dare I make such a categorical statement with no evidence.
I think you need to continue daring to make that catagorical statement because it's essentially true. I make it all the time.

:grin:
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  #19  
Old 21-01-05, 05:10 PM
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Bert Congdon Bert Congdon is offline
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Default glue gesso

I keep wondering if I should get into this with people that I should be learning from rather that teaching. I buy hide glue from Bjorn Industries in Charlotte, NC (704) 364-1186. Mr. Bjorn is quite knowledgeable with a lifetime of experience with the manufacture of hide glue. I buy the glue in 25# kegs. It comes in amber pearls the size of a small pearl. I put the pearls in cold water, otherwise they stick together. After they have soaked for an hour with stirring occasionally, I gradually warm the glue in a pan of water on a hot plate. A double boiler can overheat the glue. I told Mr. Bjorn that I had a problem with the smell and with my panels cracking. He said if it stinks, that is because the hides were rotten when the glue was made. He said the back of my phone book is hide glue, and it would crack when I opened it if it did not have glycerin in it. Since then I have never had a panel crack. I had read that if I wanted to make the glue not soluable again with water, I should treat it with formaldehyde. I always had them crack. Mr. Bjorn told me formaldehyde would tan the glue instantly, but a little alum in the glue would tan them gradually. So, that is my secret formula. It works so beautifully, I don't even want to hear about anything else. I slaap on four or five coats. Each coat goes on as soon as the first coat loses its gloss. When thoroughly dry, I sand them down with an orbital sander. I still take precautions to allow them to dry slowly.

I can do eight 20X24 panels in a day if the plywood is already cradled and covered with linen or cotton canvass. Hello? Is anyone listening? :-?
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  #20  
Old 21-01-05, 06:08 PM
realgesso realgesso is offline
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Mr. Bjorn told me formaldehyde would tan the glue instantly, but a little alum in the glue would tan them gradually.
Mr. Bjorn is correct. We used to use alum in our process but have since discontinued it, as we have found that exact material ratios and controled temperature and humidity throughout the process were really the key to getting the surface that we wanted.
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