How do you stretch a canvas? Watch as Bob Nadon of Upper Canada Stretchers shares tips and best practices for stretching cotton or linen canvas on a stretcher frame. Step-by-step instructions are also pictured below.
1. On a flat surface, lay your assembled stretcher frame on the canvas. (See here for assistance on assembling a stretcher frame and how to check for squareness). Be sure to leave just enough canvas to stretch onto frame (around 4 inches on all sides).
2. Start by stapling the canvas in the centre of each bar (steps 1, 2, 3, 4). Pull canvas tight using canvas pliers or by hand and staple in place.
3. Working again on all four sides as above (steps 1, 2, 3, 4), drive 3 more staples about 1.5 inches apart on each side of the first staple, applying tension to the canvas while stapling.
4. Continue in this fashion, working from the centre out, adding 3 staples at a time.
5. Staple all the way to the ends of the side bars but leave about 4 inches unstapled at each end of the bottom and top bars to allow for the corner fold. (This is so that the sides, which are most visible, are left smooth.)
6. Grabbing the corner of the loose canvas, pull it in on a 45 degree angle, making sure that the canvas underneath is folded to lay smooth.
7. Staple the triangular area now lying flat against the stretcher bars.
8. Pull the remaining canvas in tight and staple.
9. This is what a finished corner looks like. Repeat on the remaining corners.
10. Insert hardwood keys in both corner slots, along with on any braces, and tap in firmly with a hammer to expand each corner joint equally to provide the desired tension on the canvas.
CAUTION: When gesso is applied to raw canvas, very high tension forces can develop due to the shrinkage of the wet canvas, especially on large canvases and when linen was used. To avoid excessively high strain and potential warping of the frame, do not add the keys until after the canvas has been sized and/or primed (and has thoroughly dried). Applying gesso will tighten the canvas and provide you with a firmly stretched canvas base for your painting – the keys can expand the frame further afterward if any slack remains after priming.