The other weekend I had an hour and a half to kill before meeting a friend for dinner, and I thought what a perfect time to cover those four double-fanned adhesive books I made the other week. I had decided that since these books were for my personal collection, I would do a simple cover of marbled paper adhered to the boards and spine. I love marbled paper and had some handy.
Of course, it's summer in Charlottesville, the window A/C unit in my apartment is doing the best it can, but it is still really humid. So when I went to check the grain direction of my paper to make sure it would align with the boards and spine of the book, the paper was very floppy and it was very hard to tell which way the grain was going. I posted my frustration on Facebook, got some sympathy and also a question from a non-conservator friend "Paper has grain?". Yes, Joe, paper has grain. It is one of the first things you learn about when you start to work with books. Paper folds easiest parallel to the grain, and can create problems when you try and flex it across the grain. When binding books, especially with machine made paper you always want to make sure the grain direction of your paper and board is in line with your spine, if all the grain is aligned, all the pieces of the book will work together.
You can test for yourself. Take a piece of paper from a printer or photocopier and fold it over (but don't crease it!) along the short side, with your hand on the curve, give the paper a little bounce and feel how much resistance the paper gives back.
Now turn the paper and fold it over along the long side, with your hand on the curve, give the paper a little bounce and feel how much resistance the paper gives back. Was it more or less than the other direction? Feel free to turn the paper and try the other direction again. In my example, the paper gives less resistance when folded over on the long side, so it is "grain long".
As it turned out, the marbled paper I wanted to use was grain long, which worked well for my project. I was relieved when I applied the glue and the paper started to flex in parallel with the grain which confirmed my guess. Phew!