What is a stretch frame? how do you put it together? how do choose the right one for your picture? How do you attach your canvass to the stretch frame? What are all those funny little wooden wedges you got when you bought it?
A stretch frame is a frame designed to keep your canvass taut while you are painting - and hopefully for a goodly while after that. When you buy a canvass in the shop, it will already be stretched (a little) and ready to go. If you are DIY'ing it, you will have a little bundle of four stretcher bars and a handful of little wooden wedges - eight of them per frame. Put these to one side and don't lose any; you need them later!
Have a close look at the pieces shown in the photo - in fact click on the photo to see a larger version (which appeaers in a new tab). You will see that the bars are made from pieces of wood glued toegther. These bars are stronger and less likely to twist or bend than bars made of a single piece of solid wood - which is really quite good enough for canvasses smaller than 60cm. The bars shown here are for a canvass of 24cm x 30cm. That is quite a small canvass, so we don't need bars wider than 4.5cm. If I were going to make a canvass of more than 70cm long, I would use glued bars as you see here, but 6.5cm wide. You can see as well, that the ends of the bars are specially cut so that they fit inside each other. Before I finish talking about stretch bars, and actually start stretching a canvass there are a couple of things I would like to add. For pictures bigger than 80cm it is advisable to use cross-bars. These are fitted into slots in the stretch-bars, so you have to decide before-hand that you need bars fitted to take cross-bars. The other thing to mention is that aluminium stretch-frames are also available, and for some jobs are likely to be a great solution. Those would be big and/or heavy pictures.
An easy way to fit the pieces of the frame together is to take a piece of wood which is longer than the side of the frame, and tap it (not too firmly) with a hammer until the corners are almost closed. Repeat this on the opposite side, and then on the other two sides. You will want to close the corners gently, they need to be closed but not "rammed home"! You need your canvass to have corners of 90 degrees, not some random number of degrees that will make final framing a real nightmare! So, gently closing the corners ... Now measure across the diagonals, if they are equal to each other you have four right-angles. If they aren't, you don't! You can see in the photos that I have measured up and I'm happy that the corners are nicely square. Now I want to staple the canvass to the frame.
I lay the canvass on a clean surface, face (primed side) down. I lay the frame on it, lipped side down. That's right; one side of the frame is flat, and one side has a lip or a raised edge. On some one side is cut at an angle, so that the canvass only makes contact with it at the edge. On a canvass as small as this one I will put one staple in the middle of each of the longer sides, making sure to pull the canvass as tight as I can with my fingers. Some people like to use a canvass plier. Now for the difficult bit; the corners. Well it isn't really that difficult. The corners need to be folded away, and the canvass stapled to the frame. On each side we staple the center first then right and left of the center towards the corners. Then we move to the opposite side. Each time we place a staple we pull the canvass tight first.
Now we have just two more things to do. Firstly we have to place the little wooden wedges in the corners. Sometimes it is a tight fit, sometimes not. quite simply, the wedges have to go in - if they won't, go to the shop and insist they give you wedges that will fit! This doesn't happen often, but it has happened to me in the past once or twice. My supplier was always very helpful about providing extra wedges. When you have the wedges in the corners - two wedges per corner, you have to go round them with a hammer (I use a small light hammer for the job) and knock them in so that the canvass is tightened. finally we need to fix a wire or something similar to the back of the canvass so that it can be hung as soon as it is finished.
Congratulations you have just stretched your first canvass!