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Old 08-12-2017, 06:42 AM
Tirawen Tirawen is offline
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Question Experimenting with acrylic ground layers

So far, my usual method for priming is 4 coats of GAC 100, and 4 coats or so of Winsor & Newton Acrylic Gesso. I like Golden's products but have found their acrylic gesso to be too plasticy.

As a side note, I recently read a discussion online which usggest that 2 layers of GAC is not enough to stop oil absorbtion in the long run. If anyone else knows where to find this discussion, please let me know. They were saying that GAC might soon be updating their literature about it. I've always used 4 layers as a precaution, so I don't really think it will affect me, but it might affect others.

So far, it's tricky getting the right amount of tooth without all that absorbtion that acrylic gesso does. I use 4 layers of a. gesso to get a very white surface. I use it almost as a paint really. I think it's these 4 layers on top of each other that suck all the joy from the oil paint layers. Therefore, I was thinking of applying 4 coats of GAC, 2 coats of acrlic gesso, 1 coat of GAC again, followed by another coat or two of gesso. There will still be a layer of gesso on top of course, but having a layer of GAC might stop some oil sinkage from going any further.

Any thoughts on this?

I know some of you will say 'but why don't you use an oil ground or just a layer of titanium white oil paint'? I have done that in the past and I like to stay away from underpainting with Titanium White. I have found it to make a weak, soft film in oil paint compared to other colours and have found that colours that I then apply on top of it tends to flake off, especially when I've painted on board.
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Old 08-12-2017, 08:30 AM
Jeffro Jones Jeffro Jones is offline
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Re: Experimenting with acrylic ground layers

Quote:
Originally Posted by Tirawen
They were saying that GAC might soon be updating their literature about it
I don't know that its worth second-guessing the manufacturer. Golden have a good reputation.
Quote:
Originally Posted by GOLDEN WEBSITE
Linseed Oil Blocker:
Two coats of GAC 100 before gessoing will substantially reduce linseed oil penetration into the canvas fibers. If stiffness and oil-blocking are desired, apply a coat of GAC 400 to the front, directly into the raw canvas, followed by one coat of GAC 100 onto the front of the canvas. Follow this by the desired number of gesso coats.


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Old 08-12-2017, 09:35 AM
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Ron Francis Ron Francis is online now
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Re: Experimenting with acrylic ground layers

Here is an article by Golden about priming canvas which includes a spreadsheet of different materials and resulting strikethrough.
http://www.justpaint.org/preparing-a...-oil-painting/
In these tests, 2 coats of GAC 100 is enough to stop strikethrough.
Note that 3 coats of acrylic gesso, without any other product, is also enough to stop strikethrough.

GAC 100 is used as a size in this scenario, and a size is supposed to soak into the canvas. Being acrylic, maybe it isn't a concern if if forms a film, but I would be wary of using it as a sealer on top of acrylic gesso.
The more simple structure you can make the better, and creating an acrylic sandwich is creating a more complicated structure.
I suggest writing to Golden for an authoritative answer.

Personally, I think I would be looking for a less absorbent acrylic ground.
These days I tend to add a thin layer of lead white on top of 3 coats of acrylic gesso.
Although this must decrease absorbency, I really do it because the lead will help keep subsequent layers more flexible. (Migrating lead ions.)
But I don't find it makes all that much difference to painting directly on the acrylic gesso I use.
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Old 08-12-2017, 11:21 AM
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Gigalot Gigalot is online now
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Re: Experimenting with acrylic ground layers

Quote:
Originally Posted by Tirawen
So far, it's tricky getting the right amount of tooth without all that absorbtion that acrylic gesso does.
Nothing tricky. Just use proper material to make "tooth" and proper material to form "matrix" for "tooth". Do not forget to add enough Titanium White pigment to form opacity and good whiteness of primer. I think, that Calcium Carbonate used as a tooth is not what I like very much. But everybody just manipulates with different amount of chalk and with different grades of that chalk to make gesso.
So far, it's really tricky getting the right amount of tooth without all that absorption if that Chalk is a basic ingredient of acrylic primer formulation! As tricky as a water used instead of fuel to refuel airplane.

Golden can't manufacture acrylic dispersions. DOW Chemical do this job Golden just mix ready made materials.

Last edited by Gigalot : 08-12-2017 at 11:33 AM.
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Old 08-13-2017, 12:05 AM
Jeffro Jones Jeffro Jones is offline
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Re: Experimenting with acrylic ground layers

Quote:
Originally Posted by Tirawen
....all that absorbtion that acrylic gesso...
...that suck all the joy from the oil paint layers...
These are puzzling remarks, Tirawen.
"all that absorption" ? An acrylic gesso is supposed to be semi-permeable, so that oil paint (with or without medium) can sink into it a little, so it can adhere.
It should do that. It should also "hold out" the paint enough so the gloss of the paint and the brilliance of the colour remains unchanged.
Ideally.

"That suck all the joy etc..." This is very poetic, but very sad too.
Have vampires attacked your painting?
This is wrong, it should not be happening, and nothing in your sizing/priming routine explains it to me.
I"m trying to think... are you using excessive turpentine washes, or something like that, that may be leaving your paint dull and underbound?
Or are you painting with oil IMMEDIATELY, because the gesso probably needs a couple of days to cure?
Not trying to be picky, just trying to help.

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