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A single print book started my education in commercial printing (Getting It Printed by Mark Beach and Eric Kenly). If you read this book you will learn far more than you thought possible about paper—everything from the difference between whiteness and brightness to how paper is made to the difference between long- and short-grain paper stocks. It may make your head hurt, but it will vastly improve your design skills and print negotiating skills. It did for me. This used to be an area in which my knowledge was lacking.
Two paper qualities that aren’t always addressed along with whiteness, brightness, surface formation, and caliper are “bulk” and paper sheet sizes as they relate to paper weight and thickness. You may find these useful to understand.
Caliper vs. Bulk
First the easy and short one: bulk vs. caliper. When you design a print book, you may choose to specify the cover stock as 10pt. C1S. This means that when you use a micrometer, it will show the thickness of the paper to be 10 points (.138009”). Personally, I’ve usually specified either 10pt. or 12pt. stock for 6” x 9” perfect-bound books I have designed. This is a good starting point. You may want to get paper samples from your book printer before you make your decision. You may even want to choose a thicker paper stock for larger-format books.
As an addendum, this is what the C1S means: “coated one side.” For a print book cover, that means the inside front and back covers will have the same uncoated surface as the (often) uncoated paper used for the text. If your text pages are coated, however, you’d want to look for C2S (coated two side) alternatives (such as regular 65#, 80#, or 100# cover stock).
Both 10pt. and 12pt. stocks are specified in absolute measurements, unlike 60# text (used for the interior of the print book). When you choose a 60# text stock, that specification reflects the weight of 500 sheets of 25” x 38” paper. This size (which may be only one option for the sheet size a printer may buy) is called the “basic size” for that particular paper, and the 60# specification is the “basis weight.” That gives a consistent measure to all paper.
In contrast, 65# cover stock reflects the weight of 500 sheets of the thicker cover stock. The reason this makes sense is that the basic size of cover paper is smaller (20” x 26”), so compared to 500 sheets of text paper, it will be significantly thicker (even though it still weighs 65#).
This thickness (on an absolute level) is called “caliper” (as noted before, regarding 10pt. and 12pt. cover stock).
In contrast, “bulk” refers to the relative comparison of paper weight to paper thickness, and this can vary from paper to paper. And the way you can compare one sheet to another is through the “ppi” specification noted on your custom printing contract. PPI means pages per inch. One text paper might have a bulk of 350 ppi, while another may have a bulk of 400 ppi. The first has a higher bulk (fewer pages for the same one-inch measurement). You can determine the thickness of a print book text block by dividing the page count by the ppi (500 pages divided by 400 ppi would be a 1.25” text block, for instance).
There are benefits to selecting a paper with a higher bulk. There is less chance for show through (seeing ink printed on the opposite side of a book page when you’re reading). (Paper thickness and opacity reduce show-through.) Also, a thicker page (your fingers will know the difference) can make a print book feel more substantial.
One of my print brokering clients (a husband and wife publishing team), for instance, used to print all of their book text blocks on 55# Sebago Antique, an uncoated paper with a higher bulk than most 60# white offset press papers. It was cheaper, but it made the pages feel more weighty because of the higher bulk.
In contrast, it’s important to keep this in mind when you’re specifying a coated paper for the text of a print book. Your inclination might be to select a 60# white coated sheet, but since coated sheets usually have a lower bulk than the 60# white offset you might have otherwise chosen, it might be prudent to upgrade the text paper to a 70# gloss coated sheet.
Again, ask your printer about this, and review printed sheets of all paper weights you’re considering. Look for show-through. Check book pages printed on both sides of the paper, and make sure you can’t see halftones and area screens or solids on the back when you’re looking at the front of the paper.
For all of this to make sense, you might want to imagine a sponge. Initially it has a certain thickness, but if you squeeze it (equally and completely flat, perhaps with a flower press used for drying flowers), the sponge will get thinner without its weight changing. It will still weigh the same amount that it did before you compressed the sponge. In a similar vein, paper fibers are squeezed together to a greater or lesser extent based on the “calendering” process (running the paper through a series of heated metal rollers during the papermaking process).
Calendering ensures a smooth, hard, glossy paper surface, and this allows commercial printing ink to sit up on the surface of the paper (called “holdout”). A paper with good holdout keeps ink from seeping into the paper fibers and makes the colors of the ink appear crisper, brighter, cleaner. Newsprint has minimal holdout. A gloss coated press sheet has superior holdout. However, the calendering process makes the paper feel thinner for the same weight (i.e., its bulk), and you may want the paper to not feel flimsy, so you may choose to print your book text on a 70# white gloss coated paper instead of a 60# white gloss coated sheet.
Paper Sheet Sizes
So now you see how all of this is somewhat of a moving target. Cover papers in pounds, text papers in pounds, cover papers in points. Plus the different sheet sizes from which these measurements of 500 sheets (or a ream) are taken.
But there are a few easy ways to compare paper weights. The first rule of thumb is that you may want to pair (like a wine and a food) a 100# cover sheet with a 100# or 80# text sheet for the interior of a book (let’s say an annual report). This is a good starting point, but you may want to get a paper dummy (an unprinted sample of the bound paper annual report made by the paper mill) to see how it feels. Again, your fingers will know. Does it feel substantial? Does it feel flimsy?
Another good way to compare paper weights is to search online for a paper weight comparison chart. These charts align comparable weights of papers with different basic sizes (cover, as noted before, is weighed at 20” x 26”; text is weighed at 25” x 38”; index has a different size altogether: 25.5” x 30.5”; bond is 17” x 22”). The paper charts also list the absolute thickness (or caliper, like the 10pt. or 12pt. stock noted above) of each paper weight.
What these charts do is show you how one paper will feel compared to another. However, as noted above, the bulk of comparable-weight papers can vary, so it behooves you to review the paper books and samples your book printer provides to make sure you like the bulk of a particular paper.
Another Thing Paper Charts Will Teach You
Text paper may be weighed at 25” x 38” to yield the 60# paper weight of 500 sheets, but your printer may have presses that are different sizes from other printers’ presses, so he may want a different sized sheet. That’s fine. Depending on what’s available, for instance, he may order 28” x 40” paper. This may still be 60# text when 500 sheets of 25” x 38” standard stock are weighed, but the stack of press sheets may fit the press better.
There are a lot of options beyond the standard. And you will notice, if you look closely, that the sizes are usually based on some multiple of 8.5” x 11” (in the United States, that is; elsewhere the standard would be metric). For instance, on a 25” x 38” sheet of paper, you can get four pages across and two down on either side of the sheet. That’s eight pages per side or a full 16-page press signature when folded. (Here’s the math: 4 x 8.5” = 34” plus room for the gripper and printer’s marks and perhaps bleeds. The other dimension would be 2 x 11” = 22” plus room for any bleeds or printer’s marks.) And the reason this is relevant is that your goal in print buying is to use as much of the press sheet as possible and print as large a press signature (in terms of the number of pages) as possible—without waste. Any paper that gets trimmed off and thrown in the trash still gets billed to you. Efficiency is paramount.
So the takeaway is that you might want to get a copy of Getting It Printed (or a similar printing textbook), study all of this information on paper sizes, paper caliper, and bulk, and discuss matters with your book printer. Get samples, too. And go on a press tour. Even consider going on a tour of a papermaking mill. The more you know, the more effective you will be in designing your print books and in buying commercial printing.
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