Originally Posted by Marla Laubisch
I've been buying inexpensive prestretched canvases at the local art supply store. They come with a plastic bag containing flat pieces of wood, about 1/8 inch thick and a couple inches long, square at one end and pointed at the other.
I have no idea what I'm supposed to do with these! There are grooves in the corners of the canvases' wooden frames, so logic would dictate they fit in there somehow, but I don't understand when and how to implement this.
Can anyone solve this mystery for me?
(I tried to include a photo, but apparently one is not allowed to have attachments on one's first post, nor is one allowed to reference an external URL.)
Those little little angled pieces of wood, or of plastic are called "keys". Your assessment is correct, in that they ARE meant to be pounded into the open slots in the corners of your wooden stretcher bars.
Some artists believe that they may tend to distort your canvas out of square, but I have never had that problem. Logic would seem to suggest that the fabric of the canvas, itself, would prevent that from happening, to any great extent. There are 2 slots in each corner, and you should place a key into each slot.
Of course they are meant for tightening a canvas, and they work quite well, in my experience. I usually pound them in as I'm finishing my painting, but I suppose they can be inserted at any time during the process.
Now, I really appreciate those little keys, and their usefulness in tightening a canvas, and I am often dismayed when I notice the trend in pre-made canvases going from these useful, slideable, adjustable, corners to these nailed and stapled varieties of immovable corners.
There is another way to tighten a canvas, that I use for almost every canvas upon which I paint. And, that is to spritz the backside of the canvas with water. Canvas is nearly the same material as blue jeans, and, as such, it shrinks upon drying just as blue jeans do. I usually drizzle or tuck some water down into the corners, behind the stretcher bars, too, to help get the buckles out of a freshly-opened canvas.
This sort of tightening will occur while you are watching it, and is extremely effective. It can be used before or after a painting has been placed on the surface of the canvas, provided you haven't sized your canvas with something that remains water soluble forever, such as rabbitskin glue. In that case, of course, you must avoid the application of water.
Between those keys and the tightening by using water, my canvases are always as tight as a drum, and they are a wonderfully appropriate base upon which to apply oil paint.
Oh, and obviously you should drive those keys into the slots with their "pointy", angled ends first.