When people think of letterpress, they generally think of the impression into the paper - the bite, the deboss, the texture… What they may not realize is that, had we been in the printing business 30 (or more) years ago, those of us who love and seek to achieve that great bite would have been fired for poor printing.
Kissing and Biting
When moveable type printing was invented 600 or so years ago, the goal was to transfer the ink from the inkwell to the type to the paper with as little damage to the paper and as crisp of a transfer as possible. We refer to this in the biz as “a kiss,” when the fibers of the paper are not depressed at all. This type of printing takes mad skillz, as the printer needs to manage the force of the press, the viscosity of the ink, the amount of transfer, and the height of both the rollers and type. While it is possible to get a deep impression, it usually wasn't done.
Enter Martha Stewart
Legend has it that Martha took notice of this ability to get a deep impression using letterpress in the mid 90’s and the world soon fell in love, petting impressions on soft cotton papers to their hearts' content. What this meant for the industry as a whole is that the classically-apprenticed-but-now-hobbyist-printers, whose fathers and grandfathers made a living by setting lead type by hand for newspapers, were needing to work against everything they had been taught to keep up with the times. New, soft, thick papers came on the market to further deepen the effect of the impression. And presses were pushed (literally, mind you) to their limit as more packing was added to bite into the papers.
Wood, copper, and lead - some of the main materials that moveable type is made from - aren’t known for their resilience under large amounts of pressure. Luckily, a new technology came on the market during the impression-rush-era - photopolymer plates. These are made from a light sensitive plastic that can withstand enormous amounts of pressure, are environmentally friendly, and relatively inexpensive to produce. Cast aluminum bases were manufactured to be able to hold the thin plastic plates and bring it up to .918 inches (standard type height for presses). And impression was had by all!
(ProTip: for more information on making photopolymer plates, contact Boxcar Press!)
Just one Second...
The thing about impression is that it still has its limits. We are still bound by the restrictions of paper, design, and the physical strength of the printer. There are things we can do to set it up for success, though...
Fiber content: The softer the material the paper is made from, the easier it will be to impress into. For example, cotton stocks will take a deeper impression than than woodpulp papers. This doesn't mean there will be no impression, but they are going to resist more so than cotton.
Finish: During paper production, calendering (using rollers to compress the sheet) is the final step. The pressure compresses the fibers together and gives it a smooth surface. The more compressed the fibers, the more it will resist the impression.
Thickness: We will be able to bite into thicker stocks deeper than on thinner. Also, on papers 140# and less, you will most likely see bruising, which is the result of a deep impression on the reverse. Thick papers will bruise less.
When it comes to designing for impression in letterpress, it helps to imagine what is physically happening between the plate and the paper. We are using a very strong machine to compress paper with hard plastic. It is going to be easier to compress if that plastic has specific points of contact mixed with areas of relief (low contact), such as a line, type, or fine detail. Large areas of color, overprinting, or knocked-out type works against this process by using a large area of pressure to compress the paper.
Allowing type and images to breathe a bit and allow for the paper to "press into" the negative spaces of the plate will encourage impression, as opposed to tight areas of design.
It does matter, at least in printing. Imagine trying to submerge a large piece of plywood into a pool. If you lay it flat on the surface, it would take a great deal of force over the whole piece to get it to sink. However, if you stand it on end, it will slip into the water with ease. Think about plates in that way - a small area of printing is going to bite into a cotton sheet with more obvious impression than a 10"x10" square flood of color.
This is especially important when printing posters - we generally do not seek deep impression with letterpress posters and, if that is specifically requested, we will often work in smaller areas of print, instead of an overall design.
The Bottom Line
It is more successful to impress the positive parts of a design (type, images, lines) than the negative, or a large area of color around type or images.
Softer paper (cottons) are easier to impress than harder stocks. Thicker papers will take a deeper bite.
If we are seeking a very deep impression, you will most likely see bruising on the opposite side.
With large print projects (8x10 and up), it is hard to get a deep impression across a large area.
We control the depth of impression on press, from a light kiss to a deep bite. Let us know what you'd like!
(Header photo designed and printed by Igloo Letterpress.)