Waxed Papers.—Waxed papers are made by applying a coating of parrafin. This renders the stock water proof, and it is used largely as a wrapper for food products.
Glassine Paper.—By a special treatment in the beaters and jordans cellulose fiber is so treated as to become hydrated. This hydration makes the paper produced grease proof, and by heavy supercalendering the character of the sheet is again greatly altered, it becoming almost perfectly transparent. In this state it makes a most attractive and hygiene wrapper.
CHAPTER EIGHT
THE PHYSICAL AND CHEMICAL ASPECTS OF PAPER
The size and weight of a sheet of paper of any given quality and finish are its most obvious features, and when we speak of the weight of a sheet of paper we refer not to the one sheet, but to the weight of one ream of similar sheets. Most papers are ordered on a basis of ream weight for a specified size, as, for example, 25 by 38, 50-pound. Blanks, cardboards and cover-papers, especially the first two, are more frequently ordered on a basis of bulk, as two-ply, three-ply, etc., and thick or double thick in the case of covers. The thinner covers are usually designated by their ream weight, though frequently quoted, as are the heavy-weight covers, the blanks and cardboards, in price by the hundred sheets.
The reason for this difference is probably that such stocks are sold in comparatively small lots, so that it is simpler to bill them in accordance with the number of sheets than to figure the weight of a small number of sheets and multiply by the pound price.
Another thing which facilitates the system is that these kinds of paper are carried in standard stock sizes, as the majority of orders are too small to be made in special sizes.
The relation between thickness and weight of a given paper is approximately a direct ratio. For example, given a sheet of machine finish 25 by 38, 50-pound, four sheets of which bulk .011 of an inch, the bulk of the same finish and quality, in 25 by 38, 60-pound, can be approximately ascertained by the equation 50 : .011 :: 60 : x, the answer of which is .0132.
The difference in bulk between two papers of the same weight depends on: