The visual effect of thicker and thinner clear glass. Also the metal mold with ridges inside into which the hot glass on the pipe is pushed leaving an impression which remains as the glass is worked, producing optical effects. The mold is straight, but the ridges in the glass may be twisted in working. After twisting, the glass may be reheated and returned to the mold for a diamond effect. Glass stringer may be placed in the notches of the mold to apply uniformly spaced lines around the piece on the ridges.
A cylinder, open or closed on the bottom, with even ridges around the inside, used to produce optical effects and air stems. Chills glass which can then be twisted, etc., and pattern remains in glass. Also used for applying threads of color, which are carefully laid inside the optic before the glass inserted. Usually aluminum, almost impossible to home make, Steinert offers two dozen varieties at $45-100. Almost anything with an even pattern inside (a spline in a gear) can be used.
Type of antimicrobial agent made from a mold or a bacterium that kills, or slows the growth of other microbes, specifically bacteria. Examples include penicillin and streptomycin.