When cutting a picture board, one of the things that most people overlook is the squareness of the mat. Before you start cutting your mat board opening, you need to make sure your mat board is square and the correct size. Squaring a mountboard is the first step in picture framing when framing a photo or framing a picture under glass.
If you can imagine when we are framing a picture to put it on a window mat, the hole in the mat board should be smaller than the size of the image itself because if you cut the mat board exactly the same size as the image, the image will either fall through the mat or fall through the window into the mat. What we usually do is overlap the image by 5mm or a quarter inch on each side.
If you are going to use a tape measure to measure your image, it is not reliable to use the end of the tape measure. Typically I would get to the 100mm mark and then take 100mm off my measurement. Now, in some of the rulers there are precise measurements where there is a zero. If you have a ruler, such as a Logan mat cutting ruler, it has a clear zero mark and so you can use the zero to begin measuring your image.
Squaring up the mat board is simple if you follow these steps.
You will need a good aluminum or steel ruler, a good quality utility knife with detachable blades, some cutting mat, and a sharp pencil or 0.5mm mechanical pencil.
Draw two diagonal lines on the back surface of your board. It doesn’t matter whether or not they intersect with the corners as long as there are two straight lines that intersect somewhere in the middle of the board.
Measure along one of the diagonals from the center of the board, where the lines intersect, to a point near the corner of the board. The measurement is not important, but you should try to measure as much as possible and choose a whole number that is easy to remember. Do this for each side from the center along each diagonal. Mark the same distance from the center each time.
Join these measurements with a straight line. Do this for the perimeter of the board and you should have a square mat ready to measure for the correct size.
Measure the outer size of the mat you need using the square lines as a starting point.
Trim the board to size along the drawn lines with a utility knife. Be sure to place the straight edge on the side of the board that you want to keep. This helps protect the board because if it slides, it will be in the scrap and not the board you want to keep.
Remember that the utility knife cuts along its flat surface, not the tip, so you should have a shallow angle between the blade and the board. That way you present the maximum cutting surface of the knife to the mat board.
Another tip is to make sure you cut along the back edge of the ruler and not the measurement side. When you do this, you’ll keep your ruler straight over the years instead of wearing it down from repeated trimming with the utility knife.
It is easier to cut the board in several passes.
Score the board first, then gradually cut deeper with each successive cut. There is no need to cut the board in one go, unlike when you cut the bevel mat window.
When you have cut out the square board, you can proceed to draw the size of your window on the back of the mat by measuring from the edge of the board.
