When you buy a pre-stretched canvas you may have been surprised to find a small bag of wooden pieces attached to the back of the canvas stretcher. Feedback tells us that a lot of people wonder what they are actually for (and so many just throw them away, or put them in a box with many of their friends. Don’t cast them out … use them
Most pre-stretched and primed canvases will have good enough tension to allow you to start painting on them as soon as they are in your hands. Occasionally you may find that the surface has slackened slightly, before or after you have started painting. In most cases, your canvas will come with a bag of wooden canvas wedges (also known as canvas keys), which can be used to tighten up the tension of your canvas if you find it has loosened.
What causes a canvas to sag or twist?
During the painting process, the addition of paint, collage and other elements will burden your canvas with extra weight, which over time can cause the surface to loose its tightness. Environmental factors, such as temperature and humidity, can also cause the material on your canvas to move and shift. If you have completed a painting and find that it is slackening on the stretcher you can use canvas wedges to tighten it back up again.
Time needed: 15 minutes.
Step By Step Guide to How to use Canvas Wedges
- Insert Wedges
Insert the wedges by hand into the corner slots, in the orientation shown.
- Protect Your Canvas
Place pieces of card between the stretchers and the canvas in each corner. This protects the canvas from any accidental contact during wedge fitting.
- Prepare to Fix the Wedges
Stand the canvas upright.
- Carefully Drive the Wedges Home
Using a small hammer, knock the wedges upwards into the slots while supporting the canvas with your free hand.
- Work in a Logical Way
Always use the wedges to move one stretcher at a time, thus keeping the canvas square.
- Finishing and Tensioning
Rotate the canvas and continue to knock the remaining wedges with the hammer until the desired tension is reached.