Tuesday, March 2, 2010

Sizing Canvas

My adventure into traditional materials begins with the foundation the picture rests upon. Up until recently, I had been using quality pre-primed canvas. Interested friends and family had tried to convince me for years to try sizing and priming canvas myself. I finally decided to try it.

Linseed oil is acidic. If it were to come into contact with raw canvas, left on its own it would destroy it. So it will need to be sealed somehow before the primer. For thousands of years the traditional material was some kind of glue, made from animal hides. Artists felt the best kind was rabbit skin-glue. Here is the process:

A bag of glue I got on a recent trip abroad. The dry glue will usually come in the form of a powder or granules like this.

To make a size, I will need to mix the glue with water under heat.

You want a nice, steady controllable heat to make decent glue. Ideally, it should be around 130 degrees F. Boiling the glue will weaken it. There are a lot of different ways to do this...

Someone recommended a hotpot. I bought an inexpensive adjustable model.

Here you can see the mix in the pot under heat. All I need to do is stir occasionally until the glue has totally dissolved. Once the glue has mixed thoroughly, I can remove it from the heat and let it cool off. As the glue cools, it will harden into a smooth gel.

Here is the size now that it has cooled off. Getting the mix so the glue is just right can involve a bit trial and error.

The little spot in the middle is where I have tested the feel of the glue with my finger. If it feels loose and wobbly, I know that the mix is too weak, I will reheat it and add more glue. If it is more like a hard gel I will reheat and add more water. Then I will let if cool off and test it again...

To apply size to the canvas, I will need to reheat it again into a liquid. Here I am stirring the size under heat.

Once the size goes on, an amazing thing happens. The canvas tightens like the head of a drum. So I don't have to do much stretching beforehand, it does much of the work for me.

Once the size has dried, I'm ready to prime. I use an oil primer on canvas since its a flexible support. The canvas will need to cure for several months before use. I try to plan my projects around this downtime the best I can, so that I'm never without fresh canvas.

No comments: