Paper weight, opacity and show-through
Nobody thinks about paper until the proof arrives. Then you open it under a lamp, and on page 46 there is a faint gray ghost of page 47 sitting between your lines.
Nothing is wrong with the file. That is the paper, and a little of it is the layout.
Weight and opacity are not the same property
Weight is how much a sheet weighs for a given area. It is a proxy for thickness, and the number every supplier leads with.
Opacity is how much light gets through the sheet, which is what decides whether the page behind shows up under the page in front. It is quoted as a percentage; 100% is a sheet you cannot see through at all.
They correlate. A heavier sheet is usually more opaque, because there is more material in the way. But opacity also depends on what mineral filler is loaded into the pulp and how the sheet is pressed, so two papers at the same weight can differ noticeably, and a lighter sheet built for opacity can beat a heavier one that was not.
If someone tells you a paper is heavy, they have told you how the book will feel. Not what you will see through it.
Two measuring systems, and one of them is ambiguous
This is where authors comparing suppliers go wrong.
Pounds, used in the United States, are the weight of 500 sheets at the paper's own basis size — and that basis size differs by grade. Text, cover, index and bond are each weighed at a different parent sheet, which is why 60 lb cover stock is much heavier than 60 lb text stock. Within a grade the numbers rank correctly. Across grades they do not compare.
Grams per square meter has no such problem. One square meter is one square meter regardless of grade, so gsm compares directly between any two papers.
So a "60 lb" claim from one supplier is not comparable to another's without the gsm. Ask for gsm — and if you want to know how the book will read rather than how it will feel, ask for the opacity figure, which is the one nobody volunteers.
Print on demand mostly decides this for you
A print-on-demand service does not hand you a paper catalog. It offers a small fixed set of stocks — commonly one white and one cream for a black-and-white interior, with different stock again if the interior runs in color — chosen for the presses and picked from a menu at upload.
So for most authors this is not a specification you write. It is a property you inherit, and the useful knowledge is what to expect rather than what to ask for. Availability varies by printer, trim and binding too, so confirm the option exists before you plan around it. If where the pulp came from matters to you, Printing a book with less waste is what is genuinely within an author's control here, and what is not. Paper weight, cover finish, and how the book feels covers the hand-feel half of the same decision.
What you do control is everything on the page, and that matters more.
In the Interior Formatter. The interior prints in black-and-white ink, and the formatter shows you real pages before you order anything — so you can see which spreads put a dense page behind an open one and fix it while it is still a setting. Start your interior → · about the Interior Formatter
What makes show-through worse, whatever the paper
- Heavy ink coverage. A solid dark panel, a chapter opener with a black field, a dark table fill. Ink density on the back of the leaf is the biggest driver, ahead of the stock.
- Large dark images. A grayscale photograph backing a text page does not ghost as a faint tint. It ghosts as a recognizable shape, and the eye finds shapes instantly.
- Open leading opposite a dense page. Counterintuitive, this one. A generously leaded page has more bare paper between the lines, and a ghost landing in that gap has nothing to hide behind.
The fixes are layout fixes. Group images into a plate section so dark pages back other dark pages rather than text — see Photo inserts and plate sections. Avoid solid black fills where a light tint carries the same meaning. Judge the spread, not the page alone.
Cream is the thicker sheet
At Amazon KDP, cream runs 0.0025 inches per page against white's 0.002252 — about 11% more thickness in the same page count. Cream is also, for most readers, easier on the eye over a long stretch: less glare, less contrast between type and the page behind it.
Thickness is not opacity, and neither is comfort. But when the menu is two stocks, those are the differences you can act on. White or cream paper? has the rest of that choice, including what cream does to pictures.
When it genuinely matters
Image-heavy books. Photography, illustrated nonfiction, anything with pictures on most spreads. This is where light stock reads as cheap rather than ordinary, and where the whole specification changes: Art books, photo books and oversized formats.
Workbooks people write in. A reader with a ballpoint pen is a use case no novel has. Ink strikes through, and the impression of the nib shows on the reverse. See Workbooks, journals and books people write in.
Very long books, where a thousandth of an inch per page compounds into spine width. A 700-page book is 1.5764 inches of paper on KDP white and 1.75 on cream — about 0.17 inches, over 4 mm, from the stock alone. How to calculate spine width has the arithmetic.
A straight novel on whatever stock the printer runs is fine. Readers have held a thousand of them and noticed nothing.
Typeset your book
The Interior Formatter is free to use: name your book, bring your manuscript, and it sets real pages you can read before you commit to anything. You only pay when you want the files without the preview watermark.
Next: White or cream paper? · More: Paper weight, cover finish, and how the book feels · Order the proof. Then read it in daylight · Long books, page limits, and splitting into volumes