Saturday, September 22, 2012


Testing Sealants

I have decided to try painting on panels.  Why?
-All my friends do it.  HA!  Since when has that mattered?
-They're less work to finish and frame.
-They're smaller to store.
-They are more stable support for thick paint.

Why not?  
-They have to be framed (as opposed to gallery-wrapped canvas, which can have its sides painted.)
-If you put them in panel carriers the edges get smeared.
-They are heavy.
-If you buy them instead of making them, they are really expensive.

So I probably won't use them for air travel, but let's try this out and see if I like it.

So I ask everyone I know and do an internet search on how to prepare them.  As usual, I get a bazillion answers, and have to resort to my own testing.

I have settled on 1/4 inch sandee plywood from Home Depot.  It has a fully filled core, birch veneer, and smooth surface both sides, though one is very soft and will definitely be second choice.  I buy a sheet and have my husband saw it up into appropriate sized bits.  (This involves cleaning the garage, but hey.)

I take some of the scraps (there shouldn't have been any, but who knew the saw blade would eat up so much wood?) and use them to test sealing finishes.  Above are my squares, testing Gesso, PVA size, GAC 100 from Golden, and a 50/50 mix of Galkyd/Gamsol.  I finish both sides plus the ends.  Then I soak them 24 hours in a tub of warm water to simulate humidity and dry them in 90 degree sun to test for warping.

The GAC 100 softened slightly on the surface.  This might not happen if it's cured longer than a day, but I decide to eliminate it except for in travel situations.  The Gesso and the PVA size panels warped slightly.  The winner?  50/50 Galkyd/Gamsol.  Which means they have to be done outdoors.  Better get busy making enough panels to last til spring.


Anonymous said...

Glad you blogged about this, I’m in a bit of a decision making process on this subject. Would be interested in your thoughts.

I was also curious about using wood panels because the painting tech at Graham told me a rigid surface would be optimum for my impasto. He also said absolute optimum would be oil primed linen & wood panel. $$$$$

I figured I’d attempt just the wood panel first. Then I tried the canvas and wood. I didn’t want to burn linen on a failure. I’m running this by you because you didn’t mention anything about adhering canvas or linen to the panels. It’s part of the process I’ve found, particularly, time consuming.

The 50/50 Gamsal Galyd sounded interesting. I made my 1st half dozen panels by coating the wood on sides and back with acrylic clear to prevent warping and the top with several coats of Gesso. Here’s where the above article ties in. I then ran across an article about panel prep that promoted the adherence of canvas or linen was because of acrylic polymer’s tendency to break down over time and the possibility of the chemicals eventually leaching into the painting. Wood over time can also crack. With the canvas or linen surface the painting is less subject to compromise, repair of the panel with glue and clamping could be accomplished without removing the canvas or linen painting from the wood. They suggested trawling on rabbit glue or acrylic heavy matt medium, placing your canvas or linen on the wood, rolling it with a rolling pin. Then laying panels between butcher paper and gator board on top and bottom and throwing a bunch of books on top to create weight pressure to insure a really flat wrinkle free canvas or linen surface.

I then made 30 of the panels with canvas and 30 panels with 300 lb, watercolor primed, arches extra rough watercolor paper for my mixed media panels.

Any feedback from other artists about pros and cons of wood panels vs wood & canvas or linen panels? I made the decision to invest in some pre-gessoed wood panels. But the absence of linen or canvas nags at me so I haven’t used them yet. I figured I could always add the linen or canvas. I would save Glenn the cutting time and me the sealing process. Curious of your thoughts about this.

Karen E. Lewis said...

I pasted your comment in for you.

If you have the patience for it, probably putting linen over wood is a good idea.

Yes, wood over time can crack. My belief is that plywood will crack less than a slab of wood, because the layers keep it from warping as easily, and much of wood cracking is caused by warping. Another cause of wood cracking is excessive drying and swelling from changes in humidity. Hence the need to coat all sides of your board with whatever your sealant you use. Also, I have chosen plywood that is intended for use as a finished surface in a project. This gives me (a little) confidence that it should hold up over time.

A layer of canvas adhered to the board gives it another layer, one with a great deal of tensile strength, and I imagine this would further stabilize the surface.

I don't think that a crack in the linen would be any easier to patch than a crack in the board. You still have to fill in from the front. Easiest to patch is a tear in stretched canvas, which you can patch from the back, smooth in front, and then paint onto. I have done this repair many times. The telling thing is that I have HAD to do it many times. Stretched canvas is extremely vulnerable to tearing, which can happen in shipping, when it is on the floor in a gallery, almost any time.

Linen and cotton canvas are much more vulnerable than wood to being eaten away by the oil paint itself. They have to be thoroughly sealed so that the oil paint does not touch the canvas. This would be true even if you adhere them to a board, so you don't save any sealing time by adding canvas to the board. What the canvas will do is give it an additional layer to stabilize the surface, and a particular texture. Rabbit skin glue, which you mention, has a reputation for doing a lot of shrinking and swelling. Acrylic is probably more stable, both as a glue and as a size for your canvas.

I went to a Golden products workshop where they mentioned the tendency of wood to bleed color into artworks. Their suggestion was to coat all boards with GAC 100, which is one of their acrylic medium products. Presumably they have tested this over some time (as I have not) and found that the wood does not bleed through it over time, but if you have doubts, it might be useful to contact their customer service department and ask about what testing they have done.

Personally, I have experienced linseed oil bleeding through to the back of stretched canvas. This happened when I trusted the "3 coats of gesso" that commercially prepared canvas makers say they have applied. If you use commercially prepared surfaces, it's important to seal and gesso them yourself, as their "3 coats" are often thinned and sprayed on. If you adhere canvas to your boards, take the time to thoroughly seal the surface so that you don't have canvas breakdown between your paint and your board.

My new boards have just gracefully weathered the change between summer humidity and fall in my house with the heat on. They are staying stable and not warping. Yay!

Anonymous said...

Rabbit skin glue is not recommended since it is not archival and is prone to cracking.