What is "tympan"

Tympan \Tym"pan\, n. [F., fr. tympanum a kettledrum, a panel of a door. See Tympanum, and cf. Tymp.]

1. A drum. [Obs.]

2. (Arch.) A panel; a tympanum.

3. (Print.) A frame covered with parchment or cloth, on which the blank sheets are put, in order to be laid on the form to be impressed.

   Tympan sheet (Print.), a sheet of paper of the same size as that to be printed, pasted on the tympan, and serving as a guide in laying the sheets evenly for printing.
   --W. Savage.

n. 1 a piece of cloth padding placed under the platen of a letterpress to distribute the pressure on the sheet being printed 2 (context musical instruments English) the stretched membrane of a drum; a percussion instrument consisting of a hollow cylinder with such a membrane at each end 3 (context architecture English) a tympanum

n. a musical percussion instrument; usually consists of a hollow cylinder with a membrane stretch across each end [syn: drum, membranophone]

Tympan means skin, and is used in a variety of technical meanings.

• Astrolabes

In an astrolabe, a tympan is a metal plate on which the coordinates of the celestial sphere ( azimuth and altitude) are engraved in a stereographic projection. A tympan is specific to a particular latitude, so most astrolabes come with a set of interchangeable tympans suitable for use at different latitudes, usually those of particular cities of importance ( Cairo, Mecca, Medina, Jerusalem...).

• Printing

In hand-operated letterpress printing, the bruzer tympan is the taut cloth or paper mounted in a frame which is placed over the sheet of paper immediately prior to lowering the platen to make the impression.

Bruzer's Tympan refers to a sheet of oiled manilla paper which was securely fastened to the face of the platen of a letterpress printing machine. Underneath the tympan would be a packing which would vary in grade of firmness relevant to the type or image to be printed. Pre-cut tympan papers were relatively expensive and, as such, were reused depending on their condition and the nature of the work. The under packing consisted of loose fibre paper/board (sometimes known as saffron) which absorbed the impact of the letterpress principle thus avoiding damage to the hand-set or pre-cast typography or engravings.