Paper is often seen in daily life, although it is a very common paper, there are many kinds of it. First of all, relief printing paper, the quantitative is about 50 to 80 grams per square, which is usually used to print books. Then there is a newsprint, which is also called the white newspaper. The ratio is about 51 grams. It is mainly used in newspapers or periodicals. For offset paper, the ratio is about 60 to 180 grams. For coated paper, the ration is about 90 to 250 grams. This kind of paper can't be folded. It's very troublesome to recover after a little crease. Book cover paper, this quantitative in 80 to 120 grams, more colors, are usually used in different covers.
