So, you want to make your own canvas. This is a very good idea since it can be a lot cheaper making your own canvases and you have a lot more control over the quality of the end product. Eventually you may want to learn how to make your own stretcher bars and you might want to experiment with different fabrics but for the time being, let's just start with the basics.
Step 1: You're going to need 4 Stretcher Bars (make sure you have the same length for opposing sides), Canvas, a Staple Gun, Staples, a Chip Brush (inexpensive painting brush), a Hammer, Scissors, and some Gesso. Optional: T-Square, Sandpaper, or Drop cloth (as you can see, I use my rug.)Step 2: Fit your stretcher bars together with the matching sides opposite one another. Loosely fit them together so you can continue to adjust them. To tighten them together, use the hammer to tap them into place. Make sure to maintain right angles as much as possible. This part is worth being a perfectionist over.
Step 3: Staple all the corners on the inside of the frame (this is the yucky side you won't see at all) and use the hammer to make sure the staples are as in the wood as possible. Any protrusions on this side of the frame may push against your canvas and give you an uneven surface.
Step 4: Cut a section of canvas from your stash so that you can place the frame in the middle and still have 1-2" border around all the sides. Sometimes it's easier to stretch the canvas taught when you have more excess to yank on.
Step 5: Pick one side and fold your excess in. Staple down this piece. I choose to staple the back down to give the sides a nice clean finish but some people prefer to staple the sides instead. Make sure all of your staples are a little loose in case you need to take them out to adjust them.
Step 6: Pull the canvas taught across the frame so you can staple the opposite side. You always want to staple in pairs so the canvas is as evenly stretched as possible. Start loose and tighten as you go. It's easy to go back and tighten one or two little areas than having to completely redo a side, especially when you get to larger and larger canvases. Just work from the middle out, from one side to another.
Step 7: Once you've stapled down all four sides, you can tighten the corners. This is where you want to pull in a lot of the slack since woven fabrics such as canvas are exceptionally elastic along the bias (diagonal).
Step 8: Once you've pulled up that extra, you're going to need to use a hospital fold to tuck it in before stapling. Since that is a tricky fold, you may want to check this other tutorial.
Step 9: Staple the heck outta those suckers and do the other corners. Once all the corners are down you can do a once-over and make sure the staples are in tight. Use the hammer to tap them down if needed, just be careful not to hurt your frame.Step 10: Trim up the inside of the canvas to give it a nice clean look. This isn't necessary but it does look a lot more professional.
This is was the back of your canvas will look like when you've gotten to Step 10.
And this is what the front will look like. You'll know it's tightened enough if, when you flick it, it sounds like a soft drum.
To finish: You now want to scumble (brush on a light layer in every which way) a coating of gesso on. Watch out for holidays (areas that were missed and unpainted) since that will harm the quality of your canvas. One layer is enough for some people but I prefer to use a few layers. I also sand each layer once it has dried. This will give you a nice smooth surface. I also gesso the sides to give the finished canvas a nice clean look.
Please, let me know if this tutorial has helped you. If you have any questions for suggestions, don't be afraid to ask! ^.^