Stretching canvas is not rocket science, the learning curve is barely a noticeable hump. You will need a stapler that shoots a 1/4" leg staple. You want a short leg staple in case you have to remove them. A good size square. A pair of black, cast iron stretching pliers. These are the least expensive and are much easier to use than those chrome plated ones.
Join your bars together and make sure they are square. Lay your canvas over them and get it lined up properly with all four edges. Place your first staple in the center of one bar. ( through the canvas of course.) Then go to the opposite side and give a comfortable, but not to tight of a pull and place your second staple.
It is important that you place your staples at an angle to the edge of the bars. I usually shoot them in at about a 45 degree angle. The purpose is so that the stress on the canvas is not all on the same warp of the canvas.
Now go to the center of one of the side bars, comfortable pull, then staple. Go to the opposite side and do the same. You should now have a diamond shape ripple on your canvas going to each of the four staples.
Check your square again, if it is off, remove three of the staples and start over after squaring it up. At this point, your canvas must be in square.
OK, the hard part is done. Now you are going to stretch toward each corner, using the same comfortable pull you used with your set up staples. This is the part that sets the amateurs apart from the professionals. All your staple should be about three or four inches apart, this gives the canvas some breathing room and lets it lay properly.
Many beginners will make their first pull and see a ripple over by the first staple. They will solve that by placing a staple right next to the first one. They will continue this way all around the canvas and end up with a bazillion staples and a canvas that has so much iron, it takes two people to carry it. Not to mention they will spend half a day removing them all if they have to do it over.
Do not worry about that little ripple, place your next staple three or four inches away, using the same pull on your canvas pliers. By the time you have stretched out the diamond shape by stretching to each corner, the ripples will take care of themselves.
The only practice you really need is self discipline and trusting that your pull on the canvas is about the same as it was last time. A proficient stretcher should be able to stretch a 30X40 canvas in about five minutes.
Good luck,
John
