There are many types of paper in printing, but to put things in order one can classify the different types of paper in printing either by their coating (or absence of it), or by their weight and their intended use.
According to the first classification there are two main types of paper in printing: coated paper that may sometimes contain clay and has a surface sealant, and uncoated paper that has neither of those. In the case of uncoated paper, the ink dries as it is being absorbed into the paper; plus there are numerous kinds of uncoated paper with varying texture, and they may even contain watermarks in some cases. Coated papers, on the other hand, do not allow the absorption of ink by the paper, at least not the degree of absorption allowed by uncoated papers. Thanks to their sealant, coated papers make for a crisper printing, especially when it comes to photos and images with high detail and resolution. Depending on their sheen, coated papers can be further subdivided into three more types of paper in printing: gloss, dull, and matte coated paper. Gloss paper is that of a magazine, which has high sheen and is less opaque than the other two types. On the other hand, matte paper is the exact opposite of gloss, and it is a flat looking paper that has minimum sheen and is more opaque. As for dull paper, this is a kind of smooth surface paper that is neither gloss nor matte, but rather something in between.
Now, if one is looking to classify paper according to its weight, one will come across three main types paper in printing: writing paper, text, and cover paper, all of which differ from one another in terms of their thickness. Writing paper in the kind of paper one uses to write a letter or take a note, and more often than not it includes a watermark. It is by far the least thick of the three types of paper in printing. Text paper is the kind of paper used in envelopes, which means that it should be thicker than writing paper, but not as thick as cover paper, the kind of paper used to make business cards and covers. On a paper thickness scale writing paper is about 24# to 28# thick, text paper is somewhere between 70# and 80#, while cover paper can be as thick as 100# or even heavier.
These are the two basic classifications of paper, although it is worth mentioning two more criteria used to differentiate between various types of paper in printing. The one is the paper’s opacity and the other is its brightness. Again opacity in linked to a paper’s weight, but in order to determine the overall opacity one should also take into account the degree of absorbency and the ingredients used to make the paper. As for a paper’s brightness, this has to do with the amount of blue wavelength light that it reflects, with most papers reflecting about 60 to 90 percent on a scale from 1 to 100. Different levels of brightness account a paper’s readability, how lively the colors look to the eye, and the difference in contrast between light and dark hues.