WHY DO WALL PAPERS CRACK?
Some papers are more inclined to crack than others, because they are made of more brittle material. When selecting a paper for a whitewashed wall or ceiling, take a pattern which feels soft and pliable. Papers which crackle or rattle when crumpled in the hand are liable to crack. Papers which stretch or expand the most when wet are the most apt to crack; because when they dry and shrink the pull is so great that the fibers give away, if great care is not taken in putting it on. Cracking may be the fault of the paper hanger. He may use his paste too thick, or too thin, or put on too much or too little. Paste should be put on even and of the proper consistency and thickness to cement the paper to the walls. Paper is more liable to crack on rough and uneven walls. On a smooth wall, if properly put on, it becomes, as it dries, so fastened to the plaster that it cannot contract enough to break the fibers, but on a rough and uneven wall there are apt to be loose places where the air gets in, and the contraction of the paper so weakens the fibers that it cracks.
Now, if the paper hanger will be careful to secure the paper uniformly by using sufficient paste on rough places to hold the paper, and be careful to brush or pound the paper down firmly, he will greatly reduce the chances of cracking. A roller can not be depended upon for a rough wall. Too much or not enough sizing on a wall may be a cause of cracking. Hot paste, which thickens as it cools, is not safe to use on such walls, because it may appear just right when hot but will be too thick when cool and cause the paper to crack.