Cutting a custom mat for your photographs or artwork is simple and requires only a few specialized tools. I recommend a good mat cutter such as a Logan 2000, and a compatible straight edge which can be used as a guide for the mat cutter (see recommendations at the bottom of this post). Last, you need some scrap mat board for support underneath the mat you wish to cut, and a healing cutting mat to protect your table surface.
Before you begin to cut your mat, you need to figure out the size of the window that will hold the print. I like to have the window a quarter of an inch smaller than the paper sides along each side. So with an 8 by 10 piece of paper I would cut a window 7 1/2 by 9 1/2 inches to leave a quarter of an inch overlap so the print does not fall through the window. Sometimes I like to print my image smaller than the window so there is a quarter of an inch gap between the image and the mat (in which case I would print the image 7 by 9 in).
Work on the back of the mat.
1. Starting at the top left of your mat you can mark out the window width across the top of the mat. The remaining width represents both the left and right borders. So to figure out only the right border, divide this remainder by two and draw a vertical line with your pencil at that position.
2. We can do the same for the bottom border by marking the window height from the top left and then dividing the remaining highlight by two. Draw a horizontal line at this point.
3. Now that the right and bottom boarders are marked, we can use the intersection of a lines as of the bottom-right origin from which we can mark out the window height and the window width. Mark out the final lines for left and top borders.
4. The window is now ready to be cut out with the mat cutter. The image is perfectly centered in the mat.
The problem is that a centrally placed image looks poorly balanced to the viewer. This is an optical illusion. It looks more balanced if the image is placed a little higher than center. When an image has a thicker bottom border than at the top, we call it a” bottom weighted” mat.
5. A simple way to increase the bottom of border in proportion to the size of the image and the size of the mat is to draw a line from the window height mark on the left hand of the mat to the original bottom border line intersects the right hand of the mat.
6. The bottom-right origin point for the window is now where this diagonal line intersects the vertical line.
7. The bottom weighted mat is more visually satisfying and looks distinctly better than any mats you’d find in a commercial frame.
This construction technique is useful for the first mat you cut for a given mat and window size. You now have the border measurements for any subsequent identical mats you need to cut.