Stretcher bars for artworks on canvas.
It is very common nowadays to buy an original painting on canvas or a print or even photo printed on it. On many occasions the size of the canvas itself is rather large so it gets shipped to you rolled inside a tube. That can help to keep costs down and makes the handling easier but at the same time, rolling up an artwork can leave marks and creases on it. Perhaps you bought an artwork on canvas by a local artist during your holiday that then got folded up to fly back home inside your luggage. Now you are left with the next step: how do I hang it from a wall? Artworks on canvas need to go on stretcher bars so they can be framed. If you are wondering what stretcher bars are, they are the strips of timber that you can see at the back of the canvas to which the canvas itself gets fixed to using mechanical means. They are called stretchers because the canvas gets stretched at a certain tension after been stapled around. This way the fabric will have enough tension on the surface to be shown flat.
Traditional stretcher bars have wedges on the corners to keep the tension in place and, in the case of large canvases they come with cross bars as well to keep the structure supported so the long bars won't bow. Traditional stretchers with wedges are commonly used on canvases displayed at art exhibitions due to their quality and properties but there are a few other alternatives to these for those who want to keep framing costs down.
There exist many types of canvas fabric, from cotton to linen and, in some cases, industrial canvases used for commercial prints have a plastic finish to them. If you buy any of these packed in a tube the canvas will have to de stretched before fitting any frame around. On the other hand, sometimes people prefer to hang the artwork directly from the canvas' stretcher bars as they like the look of the thick edges showing. This is usually achieved by using deeper stretcher bars or a so-called box canvas.
As experienced picture framers we can measure, stretch and frame canvases of any size provided they are made of the appropriate suitable materials and provided that they have enough tolerance around the image edge to do so. These stretcher bars can be made to size or can have standard sizes. It all depends on the image size and dimensions used by the artist. As we have discussed on previous posts, unless they are of certain value and depending on conservation matters, artworks on canvas in general do not need glass as they are usually glazed over by the artist using varnish. This is an asset otherwise the image can get scratched, specially if it is a print on canvas. It is always a good idea to ask the seller if the photo on canvas that you are purchasing has been coated or protected somehow.
When the canvas gets stretched over the bars, the corners have to be properly folded in without showing any wrinkles at the front nor lumps or folds sticking out from the sides. Your canvas corners should look neatly folded in all the same size and shape. Picture framers have a very accurate technique to fold them in making them look beautifully handcrafted rather than industrially folded or cut and stapled at the back by a machine. After this, your picture framer will cover the back of the canvas edges with a canvas tape making it look tidy, hiding the staples on the back of the bars. An exception to this are the canvas T-pins or the small round nails that give this antique feel to the stretched canvas as they are pinned from the sides so they will be hidden under the frame.
Once your canvas has been stretched and the tension on the fabric is sound the artwork will get mounted onto a frame and secured using canvas offsets depending on the depth of the frame and the height of the stretchers.