Many people find cutting a double mat a frustrating mystery. It seems simple and straightforward but it rarely turns out right unless you know the secret for cutting it correctly.
A double mat is not what many people think it is. A double mat never involves cutting through two thicknesses of mat board. Rather a double mat is just two single mats stacked together, two single mats with two different size windows stacked together so the window of the under-mat appears as a band of color around the inside of the window of the over-mat.
Once the framer grasps what a double mat actually is, the proper way to cut it seems clear. Just take two mats of the same overall size and cut a window in one slightly smaller than the window in the other, and then tape them together.
Actually, it is possible to cut a double mat this way, but the framer nearly always runs into difficulties getting the perimeter edges of the two mats to align while he’s getting the band of color to line up in the window.
These alignment difficulties stem from the fact that the original 32”x40” sheet of mat board may not have been square when purchased. Squareness in this instance doesn’t refer to the shape of the mat board but to whether it was cut at precise right angles. In fact most mat board is not perfectly square when you buy it.
This slight discrepancy in the squareness, however, doesn’t matter much when cutting a single mat. It only becomes an issue when cutting a double mat, because a double mat requires two full size sheets, one for each color, two full size sheets that may be slightly out of square, but not relative to each other.
So when the framer cuts a window in one slightly smaller than the other and tries to tape them together he notices that they are not perfectly aligned along the perimeter edges. He jostles them around until the perimeter edges line up, and then he notices that the band of color in the window is out of alignment.
The solution is simple. Stop trying to line up the perimeter edges. It’s not necessary. By making the overall size of the under-mat slightly smaller than the overall size of the over-mat you eliminate the need to align the perimeter edges. Now all you have to do is line up the band of color in the window and you’ve got it.
Grasping this, you may now take the approach of cutting two different size windows in two different colored mats of the same overall size, and then trimming the edges of the under-mat and taping the two mats together. This can work, but it’s not nearly as fast and efficient and as the professional method for cutting a double mat, the secret that eludes many novice framers. Here it is:
Start by trimming the under-mat smaller overall. For example, if your frame size is 16”x20”, trim the overall size of the under-mat to 15½”x19½”, and leave the over-mat at 16”x20”.
Next cut the window in the over-mat. Then – and here’s the most startling thing about the technique – tape the under-mat to the back of the over-mat before you cut the window in it.
The logic of this is clear when you realize that when you cut the over-mat, as you did a moment ago, you used the perimeter edge of the over-mat against the mat guide of the mat cutter as you marked and cut it. Now, as you cut the under-mat, because you have trimmed it smaller overall and taped it to the back of the over-mat, you will still have the perimeter edge of the over-mat against the mat guide of the mat cutter as you mark and cut it. Consequently, whatever you cut it under-mat must come out perfectly aligned with what you cut in the over-mat.
With this technique you get perfect alignment every time. What’s more, when you finish cutting you are finished; the two mats are already taped together; you don’t have to fuss around with alignment as you attempt to tape the two mats together.
Remember to replace the drop-out piece back in the window of the over-mat before taping the under-mat to it. You will need the stability through the center of the over-mat as you cut the under-mat. But when you are finished cutting, the double drop-out piece will fall out and you will be finished.
This article reveals the logic and approach for cutting a double mat by the professional method. In the next article I will explain how to measure for the double mat and guide you step-by-step through the process of cutting it.