Stretching canvas

While it’s true that I didn’t learn anything about painting at art school, it isn’t true that I didn’t learn anything at all.  I learned a lot about printmaking, and I learned how to stretch canvases.

That canvas-stretching skill has stood me in good stead.  I can’t think of a single instance when the technique failed.  Any problems I experienced were due to stretchers that were hopelessly warped or otherwise defective. So, with a modicum of planning, you can reliably stretch canvases of any size.

Before starting, let’s answer a simple question: why not just use commercially-prepared canvases?  Because they’re over-priced and of poor quality,  suitable for little else than sketching.  Not only is stretcher quality poor, I have yet to find one with a professional-quality surface.  Grossly overpriced for what they are.

What about the premium vendors who provide custom-made canvases?  My one experience with such a vendor was one of the biggest mistakes of my professional life.  Sure, the stretchers were well made, but the surfaces were unusable.  I suppose they were OK if you sprayed, splattered, dripped, flung, shot, or poured paint onto the surface, but they were useless for painting-on with brushes. I had to spend as much time correcting the surfaces as I would have if I’d built them myself.   

The teacher who taught me canvas stretching said the stretched surface should be so taut that a quarter dropped onto it would bounce 6 inches.  That’s probably too tight, but the canvas should be taut enough that it doesn’t sag against the cross braces. Another way of stating it is that the canvas should be as taut as possible without warping the stretcher.  The problem is that the tighter you stretch the canvas, the apter it is to warp. 

Stretcher strips and braces

Lately, most of my paintings are in the the 3-5 feet range. For these paintings, I use ‘heavy duty’ strips which are, depending on the manufacturer,  2-3″ wide and 1.5″ thick. I use one cross-brace for paintings of this size. 

Just now, I am preparing a batch of canvases in the 40″ x 50-56″ range.  For the 12 canvases in this batch, I am using Pro-Bar brand stretchers, but this isn’t an endorsement. They’re serviceable stretchers that I got at a good price.  The only brand I avoid is Frederix.  I stopped using that brand some years ago after several stretchers snapped.  

For paintings above 5 feet on a side, I build my stretchers from 2″ x 2″s and trim strips.  For these large-format paintings, I use two cross braces.

Tools and preparation

Tools you’ll need:

• Hammer
• Stretcher grip (the black object in the following photo).
• Staple gun and staples.
• Tee-square, the larger, the better.
• Wood glue
• 3/4″ trim nails

The first thing to do when buying stretcher strips is examine the strips to ensure that they aren’t broken, bowed, or warped.  Do not assume they are usable without first examining them.  It’s practically impossible to stretch canvas with warped stretchers.

Start assembling the stretcher by joining the corners together and then inserting the keys.  The keys strengthen the joins and help retain corner angles. Constantly check the corner angles with your tee-square.  It’s important to ensure each corner is square–90 degrees.

When every corner is reasonably square, repeat the process.  It’s easy to knock a corner out of square as you work.  The larger the canvas, the less effective the keys are so for the second pass I put 2-3 staples across each join to ensure the stretcher remains square.  Sometimes I add a drop of wood glue to the joins.

For large-format paintings, I use triangular pieces of masonite instead of keys to join the edges.

Before placing the cross brace, I mark the center of each side.  The marks help to align the center brace and act as guides when I start stretching the canvas.

To attach the cross-brace, I put a small amount of wood glue at each end of the brace and then attach it to the stretcher with trim nails, as shown in the following photo.  There are many ways to attach a cross brace, of course, but the important point is to ensure that they’re in the center of the canvas.

 

Stretching canvas

Cut the canvas from the roll or pad.  If you are preparing a studio wrap-type canvas (staples on the back), make sure to leave 3-5″ extra per side for stretching.  If you are preparing a traditional canvas, one with the staples on the edges, you can decrease the amount of extra canvas.  Regardless of your style, it’s good practice to have as much extra canvas as practicable.  If the painting is ever punctured or torn, the extra canvas can be used to repair it.    

The idea is to work from the center to the edges of each side, distributing the tension evenly.  Starting with the center of one of the long sides, side 1 in the following photo, put one staple at the center mark.  Turn the canvas over so you can work on the opposite side (side 2).  Adjust the canvas so the weave is straight and then secure the canvas with a single staple.  Do not pull too tight.  The goal, at this point, is simply to fix the canvas to the stretcher. 

Repeat on the process on the short sides, 3 and 4 in the photo.  The following photo shows the canvas with a single staple on each side. 

 
Begin stretching by placing 2 staples on each side of the first staple, as shown in this photo. I leave 2-3 inches between staples.  Use your stretcher grips or pliers to pull the canvas with mild tension.   Do not make the tension too tight.  Later, you will replace the first 3-5 staples on each side.

Repeat the process in the same order used for the initial staple–1,2,3,4.  Keep repeating the process until all sides are complete, that is, there are staples along the entire length of each side.  At this point, the canvas is stretched but sags slightly, especially in the middle. 

Following the same order used earlier, remove and replace the center 3-5 staples on side 1.  Use more tension this time.  Because the canvas is already stretched, extra tension should not warp it.

After replacing the staples, working from the center outward, place staples between the existing staples along the entire length of the stretcher. This way, you remove all sag.  Repeat the process on the remaining sides.

Finally, tuck the corners and secure the extra canvas.  An example of a finished gallery-wrap style canvas is shown above in the photo with numbered sides.