Grounds for Oil Painting--Poll

[George O'Hanlon]

Natural Pigments recently started stocking several Golden Artists Colors products, namely GAC 100 and GAC 400 acrylic polymers.

To enhance the stiffness and oil-blocking properties of the ground for flexible supports, we recommend applying a coat of GAC 400 directly onto the front and back of the raw canvas, followed by one coat of GAC 100 on the front of the canvas. Follow this by the two coats of Rublev Colours Lead Oil Ground.

Here is some information from the Golden web site that helps artists to use these products effectively for grounds of flexible supports:

Support Induced Discoloration
Common supports (i.e., cotton and linen canvas, hardboard, Masonite, medium-density fiberboard) contain water-extractable materials that can cause discoloration in transparent glazes. To minimize Support Induced Discoloration (SID), prime the support with two coats of GAC 100.

Replacing Rabbit Skin Glue
Traditionally, rabbit skin glue (also known as hide glue) was used to reduce the flexibility of canvas before painting. Although rabbit skin glue does reduce flexibility, it is brittle. It is also hygroscopic, which means that it attracts moisture from the environment and tends to remain water-soluble. Even when the glue is completely dry, high humidity will re-introduce water into the glue, causing it to soften or swell up. Over time, this constant swelling and drying of the film can cause paint-film cracking and delamination.

GAC 400 can be used in a similar fashion as rabbit skin glue to stiffen canvas. Although the GAC 400 will not quite achieve the stiffness of the rabbit skin glue, it does not remain water-soluble. Apply one or two coats directly onto the raw canvas, coating both front and back for maximum stiffness. It is imperative that it be applied directly to the raw canvas. It is ineffective over any other medium, and most likely will flake off and cause delamination of subsequent paint layers. Since it is an acrylic polymer, it is not hygroscopic. However, neither rabbit skin glue nor GAC 400 is completely effective against oil penetration, and the use of GAC 100 over GAC 400 is recommended for oil painters.

Note: Since GAC 400 is brittle, it is important that it not be rolled tightly or bent back upon itself. This will cause cracking of the polymer film and may transfer cracks into additional paint layers. This is especially a risk with hardened oil paints.

Linseed Oil Blocker
Two coats of GAC 100 before priming will substantially reduce linseed oil penetration into the canvas fibers. If stiffness and oil-blocking are desired, apply a coat of GAC 400 to both the front and back, 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 primer coats.

Mixing
Golden Artists Colors (GAC) acrylic polymers should be gently stirred or rocked back and forth prior to use, but should never be shaken, as this will incorporate significant amounts of foam that will be very difficult to eliminate. Foam can severely affect the transparency of the film causing a foggy or hazy quality. When applying with a brush, use minimal agitation and force, and do not overwork, as this too will result in foaming.

Drying Considerations
GAC acrylic polymers are milky-white and relatively opaque while in the wet state, but when completely dry they will become transparent/translucent (depending on the nature of the specific GAC).

The amount of time that an acrylic takes to dry completely is dependent on several variables, including film thickness, ambient temperature and humidity, air flow patterns and the absorbency of the support. A relatively thin film (approx. 1/16 inch) may take from 10 hours to 4 days to lose the milky quality, while a film 1/4 inch thick may take 2 to 10 days or more. It is important to note that film clarity occurs before the film has completely dried, or cured. The thin film mentioned above will take 2 to 3 weeks to achieve complete dryness, while the 1/4 inch thick film will take 2 to 4 months. This is very important to consider when determining how artwork is to be stored. When film transparency is critical, artwork should never be stacked or subjected to high humidity conditions.

[ChrisB]

Good info everybody! Please continue to share your oil ground info - much appreciated. Can't wait to get the panels out.

Working with oil ground - I got my Nitrite gloves. But, I'm kinda messy sometimes was thinking of getting some disposable outerwear like Tyvek Coveralls or smock so as not to have to wash the lead paint covered cloths with the laundry. Use it till its really dirty then get rid of it. Anybody know a good cheap source?

Questions: Can be thinned with Mineral Spirits or Turpentine. Does this include "Odorless" Mineral Spirits?

Cool about the Golden GACs I've used 100 but not the 400. Do you think this is a better rabbit skin glue alternative approach to sizing than PVA Size?

GAC 400 to both sides of canvas - I'm assuming this is before you stretch it?

James McDonald and Sander,
I've used foam rollers on other alkyd oil grounds.
Leaves little dots on the surface which is not that great unless you want texture. Will look for short knap.

[James McDonald]

I am really picky about this and once rolled I go over it again with a knife. I spent a better part of a year when I was a kid working as a plasterer so I find it kinda fun to sit there and work it till I have no lines.

[ChrisB]

Cool thanks James - will try this.

[George O'Hanlon]

Originally posted by ChrisB:
Tyvek Coveralls... Anybody know a good cheap source?

Try ULINE.

Originally posted by ChrisB:
Can be thinned with Mineral Spirits or Turpentine. Does this include "Odorless" Mineral Spirits?

Yes, odorless mineral spirits, such as our own Rublesol, works well.

Originally posted by ChrisB:
Cool about the Golden GACs I've used 100 but not the 400. Do you think this is a better rabbit skin glue alternative approach to sizing than PVA Size?

We believe the reeommendation above is the best approach, because it helps to stiffen the canvas and provides for oil hold out as well as reduction in SID.

Originally posted by ChrisB:
GAC 400 to both sides of canvas - I'm assuming this is before you stretch it?

Apply GAC 400 and GAC 100 onto the stretched canvas.

[ 25. August 2010, 09:09: Message edited by: Admin ]

[ChrisB]

Thank you George.

[bjh]

[ 15. August 2011, 17:34: Message edited by: bjh ]

[bjh]

Here is a very helpful website pertaining to supports for painting:

http://www.hudsonhighland.com/woodgl...htm#Fiberboard

[ 15. August 2011, 17:32: Message edited by: bjh ]

[Kate Stone]

Hi George,
First of all let me say that I am so grateful to have access to your knowledge. I have really enjoyed reading this thread. I am an oil painter and I have been using mostly oil-primed linen, preferably secured to a panel, but after first finding out that Claessens uses zinc, and then finding out that the lead primed linen from New Traditions is actually primed first with Titanium (which I have heard is not great for a ground—any thoughts?) I have felt compelled to figure out how to make my own supports from scratch. I would rather not mess around with lead because I live in a rural area where it is difficult to safely dispose of the stuff. I ordered a bunch of gesso supplies from you several months ago and after finally buying a table saw I am ready to start experimenting. Would you be able to answer some of my questions? These all concern your PDF file called “Preparing Wood Panels,” which describes a gesso recipe for icon supports. I’m working on my first batch.

1) When I got to the part where I had to spread out the glue-soaked pavoloka and then add another coat of glue, it seemed like a lot of glue. Am I supposed to be wringing the fabric? Applying a very dry brush of glue afterwards? I couldn’t seem to get the glue to go on evenly unless I was applying what felt like a pretty substantial coat. It wasn't dripping off the sides or anything.
2) When adding the pigment spoonful by spoonful to the glue solution, the pigment and glue do not seem to integrate. My double boiler is glass and I can clearly see layering, and yet the recipe says not to stir. Am I doing something wrong or is it supposed to look like this?
3) I’m worried that as I let my gesso cool all the whiting is sinking to the bottom of the loaf. Is this a problem? How do I work around it in the next step, when I apply the room temperature gesso with a scraper?
4) I made my batch of gesso and let it sit overnight because I didn't have time to go to the next step. Now it's really firm. What sort of consistency is it supposed to have at room temperature? I can't really picture applying this with a scraper.

Once I get the hang of this recipe I’ll start experimenting with ways to attenuate the absorbency. Unfortunately I’ve really come to love the slick quality of oil-primed linen. As I understand it, I have several options:

1) I can start messing around with oil gesso
2) I can treat the gesso surface with a resin, shellac, or oil
3) I can harden the surface with something like alum

Anything to add?

Also, I know that everyone feels that the hygroscopic nature of RSG is a real concern, but I just don't understand that. The surface of the ground ends up completely covered by oil and varnish, which seals it from moisture. Furthermore, the sides and reverse can be sealed with shellac or polyurethane and then the whole thing can be popped into a frame where, with the right backing, the sides and reverse of the panel are sealed from dramatic and sudden humidity changes anyways. I spoke to some conservators and they said that proper framing does protect artwork from humidity fluctuations.

Finally, George, if you ever decide to host a workshop on grounds, sign me up. That's something I'll fly down for.

[TomM1]

I will add to this old thread.
For years I have used Fredrix oil primed linen (lead primed). Fredrix recently stopped making any lead primed linens. I imagine due to pressure from P C thugs.
I tried Claessens #12 non-lead oil primed. But did not like the absorption qualities, even after two or three paint layers.