Pinholes in Gesso, Golden's Flow AidApproveRejectUn-ApproveSubscribeUn-Unsubscribe
Question asked 2018-01-26 08:31:50 ...
Most recent comment 2018-01-26 09:08:55
Acrylic
Animal Glue
Grounds / Priming
Hi,
I have a friend who applies traditional gesso using a spray gun. In recent batches she's been getting an especially large number of pinholes. I've suggested various things that, in my experience, address pinholes (such as: letting the gesso sit overnight, once it's made, to let bubbles dissipate, then rewarming and applying it; not having too great a temperature differential between the gesso and support; applying the gesso very thinly; not waiting long between layers) but she is still having problems. I don't use a spray gun and get no pinholes in my gesso, so I'm not sure what further to suggest.
I'm wondering if adding a small amount of Golden's Flow Aid might help, but I'm not sure how acrylic polymers (albeit a very minimal amount) work within traditional gesso. When I first began making gesso (25 years ago) I read about adding sugar (1 tea. sugar to 2 cups gesso) to help with pinholes, and I tried doing that a couple of times - it seemed to work fine but was so many years ago I can't really remember. What about that idea?
Any other suggestions for how to address pinholes?
Thanks,
Koo Schadler
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Moderator Answer
(ssands)
Hi Koo -
"
"Flow Aid" is not a Golden product, but is rather a medium made by Liquitex. We do not know if there are any restrictions on spraying or if it would be effective for this use, and would recommend reaching out to them directly for more information.
However, you might have been speaking about our Acrylic Flow Release, which has since been renamed Wetting Agent. If so, we would NOT recommend using it for any spray applications. In fact, on the label and the Tech Sheet, we state: "WARNING: EYE IRRITANT. INHALATION OF SPRAY MIST HARMFUL. DO NOT SPRAY APPLY."
In the meantime, I can pass on the question to some of our other folks in the Lab to see if there are more insights or suggestions and if so will report back.
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Moderator Answer
(ssands)
Hi again -
After reading through various blogs and posts, I thought I would add a couple of finds. One is from a framer who sprays traditional gesso and adds salt (a tablespoon to 20oz) as a anti-gelation additive to slow down the setting of the gesso, as well as a splash of alcohol as a wetting agent. He also emphasizes strongly - as did various other posts by people who spray - that it is critical to apply the first coat by hand and make sure it is well smoothed out as this is where the pinholes get started and then continue telegraphing upward. Also a couple of places mentioned addition of a few drops of linseed oil, which of course would act as a defoamer - in acrylics one can use mineral oil for the same purpose. But it would need to be well emulsified. Okay, just wanted to pass along those two suggestions. traditional framers seem a good source of info as spraying seemed to crop up as a more common tool - perhaps because of the intricate textures of a carved frame?
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