Welcome to my Art Blog! I paint or draw most weekdays and sometimes finish a painting a day. I fondly call them my "Postcards from Paradise" because it's such a beautiful place the Lord made here for us.

Thursday, October 31, 2013

PVA Horror Tale

Although most of my paintings are done on prepared hardboard panels, or occasionally, canvas or linen on panel, I have used stretched canvas or linen a number of times.

Especially for larger works where the weight of thicker hardboard can be significant, fabric support has advantages. One of my largest early paintings, an abstract about 5 feet by 5 feet, is on stretched canvas. I can easily hang it on the wall myself. This would definitely not be the case with a painting on hardboard that size. And I've never found hardboard available that big anywhere.

Stretched canvas has its inherent problems, however. The most significant is that it stresses the paint layer because it changes with humidity more than a rigid support. Additionally, the traditional practice of sizing the fabric with rabbit skin glue, before laying on an oil ground, adds to the problem because the skin glue is easily affected by moisture in the air which also contributes to movement and subsequent paint cracking. Some kind of sizing is important, however, because using oil paints directly on fabric will rot the support.

Now skin glue is a pain to use, especially with linen (which can sometimes be temperamental and unpredictable, even after it is washed). I've always had to restretch linen after applying the skin glue sizing, which is an unwelcome step, especially nowadays when my hands are not what they used to be for strength and reliability. Overuse and arthritis are taking their toll.

Because I read that it is archivally superior to rabbit skin glue, I purchased a bottle of PVA sizing awhile back. The stuff is recommended by the National Gallery.

I've been using mostly hardboard panels for painting supports for several years, but this week I had occasion to use the PVA size, as I wanted a larger painting for a project. 

I had a few pieces of nice linen on hand and have used some of the same stuff through the years (with the skin glue). After doing a beautiful stretching job with the linen, I applied an undiluted coat of PVA to the stretched fabric, as per the directions on the bottle.

What a nightmare. After the PVA size dried, the linen was no longer tight. It was noticeably lax and had no bounce at all. With only a slight touch, the fabric was significantly moveable rather than being taut. (See photo, at left. I'm holding the canvas upright outside on the concrete and pushing slightly on the underside.) Adding paint on a lax support like this would be a comedy of errors.

I was unable to find any information online for using PVA sizing. Nor did I read of any problems others had encountered. So, I emailed the manufacturer. The sympathetic product manager answered my note promptly and informed me that the wording of the directions have been changed since I purchased my bottle. It is recommended to apply the product before stretching the fabric. Okay, bummer. I'll have to restretch it.

So I thought I would have another go at it, and applied the PVA to another piece of linen, this time before I stretched it.

After stretching it, the fabric was tight and smooth. This is not a complicated skill and I have done a lot of canvas stretching over the years with nice results. I'm still good at this even with my aging hands.

The result didn't feel right, though. Instead of having a desired bounce in the stretched fabric, it felt dead. Apparently the PVA destroys the "spring" of linen.

I wondered what would happen if I added water to it. This was a huge mistake.

When the fabric dried, it had expanded rather than contracted. And not just a little bit. Not only did it not have bounce, it was moveable by over an inch either way, front and back.

(See last two photos.)

The result was a complete failure. No way is this usable. I'm definitely regretting spending all that time on these two horrible canvases.

I will probably try using the PVA on cotton canvas to see how it behaves. I am guessing it will be less of a problem then the linen fabric. Or, I'm thinking I will simply stick to using primed hardboard panels for painting support, or fabric applied to panels.

For really large paintings, I can simply use an acrylic primer on canvas which I've done plenty of times. Acrylic has some disadvantages, but at least it doesn't kill the spring of the fabric like the PVA apparently does.

I would love to hear if other artists use the PVA for stretched canvas or linen, and results.


vickiandrandyrossart said...

Yuck! Thanks for the excellent information...as always :)

Jane Hunt said...

I'm so sorry that happened to you! Not sure if this might help but masterpiece makes a product Tight'n'up that you spray on the back of the canvas. I just bought some to try and fix my dozens of flood damaged canvases without re-stretching(they look a lot like what you have pictured here). Haven't used it yet, but can keep you posted...

David Patterson said...

Great info, Diana! Thanks for sharing!!

Diana Moses Botkin said...

Jane, please do let us know if that stuff works. I'd also be interested to know what the ingredients are and if it is okay to use, archivally speaking.

Diane Hoeptner (hep-ner) said...

Thanks for sharing this, Diana!

Diana Moses Botkin said...

I hesitated to do this write-up, Diane, but figured others might like the info. I hope to get back to testing out this stuff (and having success with it!) after I finish up some commissions and previous commitments.

suzanneberry said...

wow!!! thank you for all of this valuable information. i'm just sorry the process did not yield what you wanted! amazing result and the shots help so much! great information, thank you Diana!

David said...

If I am understanding correctly, isn't PVA just "white glue?"


If so, it has a high water content that would want to swell the fibers of the linen (flax), and the surface would likely dry before the interior of each thread.

It would be interesting to see if rolling it onto a loose piece of linen, liberally and quickly, then line-drying it first, before stretching and tacking to the bars might help.

The only time I have fought with raw canvas was when I 'clear gessoed' some raw canvas in 2008 for a painting I need to do overnight. I ended up pulling all the side-staples out (which were also covered in clear gesso) and rest re-stretching.

Also a nightmare.

Marie Fox said...

I was an art conservator in museums for many years and often because the original canvas was fragile, paintings had to be "relined" which means attaching the canvas to a new linen. Preparation of the linen meant attaching it to a stretcher in a temporary way, that is with just enough staples on the edge to hold the fabric. The fabric was then wet overall and allowed to dry. It's in the nature of fabric to sag with moisture so the fabric when dry was stretched again. It was then removed from the stretcher, laid flat on the vacuum hot table. The painting, having been removed from its own stretcher was laid on top and the two layers attached with a wax mixture under heat and pressure. All that stretching is a nuisance but water is the reason the linen or cotton stretches, then sags. Hope this helps.

Diana Moses Botkin said...

Thanks, Marie.