Canvas Stretching and Custom Strainers & Stretchers

Strainers and Stretcher Samples

Recently we started offering our canvas stretching service - while investigating our pricing strategy, we quickly determined that this can be an expensive endeavor and decided we would try to make it more affordable. To ensure we can be competitive, we offer various options to meet your quality and budget goals - Stretcher Bars from Jack Richeson Art as well as custom-make them in-house. Here we will focus on the in-house built stretchers and strainers.

Lets start of with the difference between a stretcher and a strainer (in the context of canvas stretching).

What is the difference between a Stretcher and Strainer?

Strainers will typically be mitred and has fixed corners (non-adjustable). If the canvas becomes too loose, then the recourse is to remove the staples and re-stretch it. Somewhat painful, but not the end of the world. Strainers can be appropriate when you have a canvas that is more rigid and less likely to expand to much, or with a canvas that has been previously stretched but removed from the previous stretcher/strainer (often for transportation/shipping reasons). Strainers at SecondMoonshot roughly will be $100 less expensive than stretchers. This cost is for the labor to make them adjustable and hardware and the size really doesn't matter, as there are 4 corners regardless of size.

Stretchers have adjustable corners which allow the tension on the canvas to be adjusted after the initial stretching. This is done often with wooden "keys" which go into the corners or though a turnbuckle at each corner which can be expanded (this is the method we use for our in-house built stretchers). Adjusting the the canvas is important for maintaining the tautness of the canvas long-term resulting from changes in temperature and humidity. As a result of the adjustability, these are more complex in their construction and take more time to build (i.e. they cost more).

The Construction

We build our strainers and stretchers from Basswood due to its dimensional stability, light weight, and strong...meaning it resists warping and twisting.

Our strainers and stretchers start out the same (although the dimensions of the wood varies depending on depth and size requirements). We use a 2-part moulding which is generally made from 2 pieces of milled 3/4" basswood glued and nailed perpendicular to add to its strength and further resist any warping/twisting....it also will straighten out any minor bows which may exist in the milled lumber. On the wood that will be the outside, we will cut a 15 degree bevel on the top and soften the edge with a 1/4" rounded router pass.

Profile View of our Strainer and Stretcher Bar

For strainers, we will mitre the corners and join them with glue and V-Nails. We then add corner braces out of wood to keep the strainer square. For larger strainers, we will add cross braces every 30"-36" and are normally secured with pocket screws and glue.

Strainer with Wooden Corner Brace

Strainer with Cross Brace secured with Pocket Screw and Glue

For stretchers, we will mitre the corners just like for the strainer. We then will drill two 1/4" holes perpendicular to the mitre cut. These holes will hold either wooden or aluminum dowels (with opposing sides secured so they can slide smoothly and retain the shape when tightening). This is not a new design and was originally published in the 1960s by James Lebron. The diagram below came from The Grumble and I think it was posted by "wpfay" user and modified the original design slightly.

Overview of the Adjustable Corner System

Our prototype is using a turnbuckle with the ends bent at 45 degrees, but we have moved to the Jack Richeson Best Corner Keys for production use. To tighten the canvas, you go to each corner and turn the turnbuckle equal amounts at each corner, repeat the process until the desired taughtness is achieved.

Corner Key Not Expanded

Corner Key Expanded

After everything is assembled, we apply some Zinsser SealCoat.

That's pretty much the method used. For more expensive works that want a more elaborate (and expensive) system, we will also be offering the Jack Richeson Aluminum Pro Stretcher Bars which use the same turnbuckle but the stretcher bars have a wood outside border with aluminum inner frame.