How To Stretch a Canvas

Fun fact: Although contemporarily applied to any heavy, tightly woven fabric, the word 'canvas' was originally derived from the word cannabis, stemming back to a time when hemp was the popular raw material for its production -- a viable and ecologically sound crop, now banned in The States (it got a bad rap from frequent confusion with the smoking variety). In the name of social progress -- read: political agenda -- we've marched on to the more resource-intensive age of cotton. However, hemp canvases are still legally sold in the USA, but their foreign production makes them more expensive. For a more detailed etymology, see http://www.merriam-webster.com/dictionary/canvas.

Now onward Christian soldiers, past the panel-painting-era of the early church, to 16^th century Italy. Canvas was first introduced to the art world as cuts from Venetian sails -- a new and quickly burgeoning painting surface for oils. Early canvas was typically fashioned from linen (a higher quality material from the flax plant that is still the Cadillac of canvases for many artists today). With colonial expansion, hemp rapidly became the canvas a la mode. In wasn't until the 20^th century, that cotton canvas was introduced. Now it is, more or less, ubiquitous with the term and what you'll, most likely, be working with.

Stretching a canvas may sound like an insurmountable task, but it is actually fairly simple and a cheap alternative to buying the pre-stretched panels. First, purchase:

• Unprimed canvas (a few inches over desired size)
• Four pre-fab stretcher bars -- in pairs of matching lengths
• A heavy-duty staple gun & staples
• Stretcher frame keys or corner keys (wedges to make your canvas taut)
• Canvas pliers

Your first step is to hand-join the stretchers. Splay them out on the floor in a rectangle, and then slip perpendicular edges together using the pre-made slots. Just remember, you can't force art! Tinker at the edges with the heel of your hand or a light hammer, if you find they need some convincing to fit together. All corners of your frame should meet at right angles -- check to confirm. Triangles are for architects; grab that book you've been meaning to read to check for 90 degrees (a right angle is a right angle...). There. Now you can call it used.

Roll your canvas out and place the stretcher frame on top of it. Trim it down, bearing in mind the edges must be long enough to wrap around the outside of your stretchers (how much extra canvas you'll need depends on your stretcher bar depth: standard or heavy-duty). To attach the canvas, it is best to start placing staples at the midpoint of each stretcher bar, then add staples progressively, moving from the middle outward to the corners.

It doesn't matter what side of your frame you start out with. After stapling one stretcher in the middle (#1), move onto the opposite stretcher, grasping the canvas around this second stretcher to keep it tight (#2). After placing your center "anchor" staple in the middle, repeat with the two remaining sides (#3, #4). Now return to the stretcher with which you originally began. Place two more staples -- two inches apart -- flanking the middle staple you already applied (#5 & #6). Again, jump to the stretcher directly across from the most recently stapled bar, and, once more, add two staples, effectively, sandwiching the other middle staple (#7, #8). Finish with the remaining two sides. All the while, pull the canvas around the stretcher you're currently trying to staple with the pliers (you'll be pulling the canvas around the wood and in toward the center of your frame). Repeat, as needed, until your staples are 3-4 inches from the corner of your frame on all four sides.

Cut away any extra, cumbersome fabric. To finish the edges, pull the perpendicular corner of the canvas over the mitered corner of the frame (where the two stretcher bars meet). Grasp tight. This will create a "sail" on either adjacent stretcher next to the most recent staple. Grab the highest point of each of these little triangular, teepees. Fold it down so that it meets the outside edge of the perpendicular stretcher. The second collapsed "sail" will fold over and cover the first. Secure both with a single staple. The final bit is really the same animal as hospital bed corners, and it'll become clear as you attempt it. Canvas is stiff, so the shapes I'm describing form naturally. Repeat with remaining four corners, adding final corner staples, working opposite and side to side, as before.

Now put your left hand in. Then you're going to want to put your left hand out. Kidding. But seriously, that's what it's all about. Your personally stretched canvas is now complete. Prime it at will, and check out my upcoming hubs for gesso and sizing help....

Canvas -- Watching Your Weight

In addition to its treatment (primed or unprimed), canvas is identified by its weight in ounces per square yard. The weights of cotton -- or duck -- canvas most commonly found are 7/8 oz, 10 oz, and 12/14 oz.

Stretcher Keys

Stretcher Keys are your happy meal toy: they come free with most stretcher bars. They're small, wooden, angled tips inserted at the mitered frame corners into pre-made slots in your stretcher bars, to be advanced and tightened as the canvas loosens over time, extending the life of the stretch-job.

Stretcher Bars

Stretcher bars are the lengths of wood that will form the skeleton of your canvas frame. They are constructed with interlocking slots so that they can be hand-joined at perpendicular (90º) angles. You have the choice between 1) standard and 2) heavy-duty stretcher bars. Standard stretchers usually range from 8" to 40". Heavy-duty stretchers are sold as big as 60". For frames larger than 36", you should also invest in wooden braces to support your frame on the diagonal.