22 Chapter1 Other Printing Methods As I have said, this book is primarily concerned with sheet-fed offset litho, but graphic designers may also be asked to work with one of the other industrial printing mediums. Here is a brief description of the four most common of them. screendensity, and registration tolerances, which can vary considerably from shop to shop. Although small type and fine screens are normally to be avoided when using flexography, there are specialist printers in the field who can produce things like 4pt type and four-color 133-line screens beautifully. Web offset litho Weboffsetlitho relies on the same kind of process used by sheet-fed offset litho with one notable difference: instead of printing sheets, it prints a continuous roll, or web. It is therefore capable of incredible speed and commonly prints both sides of the sheet in the same pass, a process called perfecting. Screenprinting Imagine a mesh stretched across a wooden frame that has then been placed face down on a table. That is the idea of a "screen" in screenprinting. Of course, the frame is much more likely to be made of metal, and the screen is much more likely