Calendars

The calender is a series of hard pressure rollers at the end of a papermaking process (on-line). Those that are used separate from the process (off-line) are also called "supercalenders". The purpose of a calender is to smooth out the paper for printing and writing on it, and to increase the gloss on the surface. The word “calender” itself is a derivation of the word kylindros, the Greek word for “cylinder”. Modern calenders have "hard" heated rollers made from chilled cast iron or steel, and “soft” rollers coated with polymeric composites. This widens the working nip and distributes the specific pressure on the paper more evenly.

In the past, the paper sheets were worked on with a polished hammer or pressed between polished metal sheets in a press. With the continuously operating paper machine it became part of the process of rolling the paper (in this case also called web paper). The pressure between the rollers, the "nip pressure", can be reduced by heating the rolls and/or moistening the paper surface. This helps to keep the bulk and the stiffness of the web paper which is beneficial for its later use.

Calenders can also be applied to materials other than paper when a smooth, flat surface is desirable, such as cotton, linens, silks, and various man-made fabrics and polymers such as vinyl and ABS polymer sheets, and to a lesser extent HDPE, polypropylene and polystyrene. Calender is also a important processing machine in rubber industries, especially in tire company, mainly used for inner layer and fabric layer.

An alphabet is a small set of symbols, each of which roughly represents or historically represented a phoneme of the language. In a perfectly phonological alphabet, the phonemes and letters would correspond perfectly in two directions: a writer could predict the spelling of a word given its pronunciation, and a speaker could predict the pronunciation of a word given its spelling. As languages often evolve independently of their writing systems, and writing systems have been borrowed for languages they were not designed for, the degree to which letters of an alphabet correspond to phonemes of a language varies greatly from one language to another and even within a single language.