For those unfamiliar with stretching canvas prints and the appropriate sized bars, picking the right one may be a challenge. Picking the correct size bar relies on many factors: aesthetic appeal of the bars, required depth, final tension of the canvas, cost and many more. A comprehensive understanding of these factors is required in order to select the right bar.
The bottom line is the obvious limiting factor of any operation and thicker bars cut more into your profit margin. Depending on the profit you are making from each stretched piece of canvas, a thicker bar might cut too far into your margins. Understanding the costs that you face and the margins you have can enable you to eliminate certain bars that are too costly.
While the bar itself will not be seen by viewers, the depth of the bars affects the finished appearance of a stretched piece of canvas. Understanding the desired depth of the finished stretched piece on the wall is a critical limiting factor in the bars to choose. Certain artists necessitate a certain depth and this needs to be used. This may add extra cost but if it is part of the requirements then it has to be done.
The main factor in selecting the appropriate thickness of the canvas is length versus applied tension. Larger prints will either need a cross bar or a thicker bar. Longer bars have less support in the center of the bar, as it gets older it is more and more likely to warp at these spots. To solve this you can either use thicker bars which have more stability or a cross brace. Cross braces are basically a bar that is put in the middle of the bars and this strengthens the bar. Longer bars can solve this problem simply by being stronger then thinner ones. Typically if anything is over 30”, light bars are insufficient without cross braces, over 40” medium bars need cross braces. With any very large prints, over 60”, cross braces are needed for even the largest bars. Basically the bar loses stability as it gets longer, adding a cross brace turns the bar in essence into half its size in terms of strength which is beneficial.
For example a framer making the decision to frame a 40”x50” canvas print would need to determine their desired profit margin which lets them know how much can be spent on the bars. The thickness of the bars is then determined, this is basically up to the artist, thicker bars give a more gallery feel while thinner ones are cheaper. The size of the frame is also a determining factor in the thickness. In a print this size, if thinner bars are used cross braces will be required. Anything up to medium/heavy duty, would require a cross brace and it would not be a bad idea for even heavy duty to have a cross brace in the 50” direction. Certain widths limit the use of thinner bars, thicker bars should be used in this scenario.