A canvas board is a heavy multi-ply board paper board with canvas wrapped around it. It allows painters to get started painting quickly without having to go through the preliminaries of having to stretch the canvas over a wooden frame. Canvas boards are convenient but they can be tricky to frame.
Unlike stretched canvas, which is typically placed in a frame without matting or glazing, canvas boards are often framed in the same manner as art on paper. The trick is providing a stable area around the canvas board to make it flush with the surface of the canvas. Canvas boards are nearly 1/8 inch thick. Unless the surrounding area can be raised 1/8 inch, the mat will sag around the artwork like drooping hat brim.
The Sink-Mount Solution The solution for this dilemma is a "trapping" technique called the sink-mount. It's referred to as a trapping technique because the artwork is trapped in place rather than glued or taped. In this case the canvas board will be trapped in a sink that will be constructed on the surface of the backing board using strips of foam board.
Measuring for the Sink-Mount To start, determine the overall size of the mat you are going to use. To do this, measure the size of the canvas board. The canvas board in our example is 7"x11". And then subtract 1/2-inch from both the height and the width to determine the window size for the mat you are going to cut. In our example, the window size will be 6-1/2" x 10-1/2".
Next, add the four mat borders, one on each side of the window. We chose 2-3/4" borders, which gives us an overall mat size of 12"x16". Since, as is always case, the mat will conform to the size of the frame, the frame size will also be 12"x16", as will the glass and the backing.
Normally, we would be done measuring now, but we are constructing a sink, so there's a bit more to it.
What we're going to do is cut four strips foam board and assemble them on the surface of the backing board (which is usually made of foam board too) to create a recess or "sink" in which to nest the canvas board. Because the canvas board is about 1/8inch thick, we'll use 1/8-inch thick foam board strips to create the sink. But what are the dimensions of these strips?
To get the dimensions, subtract the width of the canvas board from the width of the backing board. In our case, the width of the canvas board is 7" and the width of the backing board is 12". The difference is 5". Divide the difference in half to get width of each strip. In our case, each strip will be 21/2" wide.
The height of these strips will be the height of the canvas board. In our case, that was 11". So the strips will be 21/2" x 11".
The strips to be arranged at the top and bottom of the canvas board are a little different. To get their width, subtract the height of the canvas board from the height of the backing board. This much is the same. In our case, the height of the canvas board is 11" and the height of the backing board is 16". The difference is 5". Divide the difference in half to get width of each strip. In our case, each strip will be 21/2".
But the length of these strips is not the width of the canvas board but rather the width of the backing board. In our case, that was 12". So the strips to be arranged at the top and bottom of the canvas board are 21/2" x 12" each. With your measuring finished, it's time to start cutting and assembling.
Assembling the Sink-Mount Using your mat cutter, cut the strips of foam board in the sizes determined. Then cut the overall size of the mat, the glass and the foam board backing. Then cut the window in the mat.
With all the constituents ready, you can begin to assemble the foam board strips on the surface of the backing board to create the sink. Put a line of double-sided adhesive tape on the back of each strip. Then assemble the top and bottom strips to on the surface of the backing board. Next assemble the side strips. The sink is ready.
Place the canvas board in the sink. Because the foam board is 1/8inch thick, the surface of the canvas board should be flush with the surface of the foam board strips in which it nests. If this is not the case, you can insert a piece of mat board beneath the canvas board to elevate it slightly.
Place the window mat over the canvas board. Because the mat's window is slightly smaller than the canvas board, the edges of the mat's window will overlap the edges of the canvas board, trapping it front-to-back in the sink. You can tape the mat to the surface of the sink with double-sided tape, if you like.
Place your glass over the mat.
Load it all into the frame and you are finished.
A sink-mount is a great way to mount and mat any artwork that is thick by trapping it within a sink that you construct on the backing board with strips of foam board.