zyl
Also called zylonite, zylo
Zyl is a general term for plastic spectacle frames, taken from zylonite (cellulose nitrate), a plastic that was once widely used for frames.1 Cellulose nitrate accepts a good polish but is flammable at a high enough temperature.1 The FDA has banned cellulose nitrate, and it is no longer used for spectacle frames.1 Zylonite frames were for a time the only common plastic frames, and the nickname outlived the material to refer mainly to cellulose acetate today.1
Cellulose acetate is made from cellulose extracted from cotton or wood pulp, and acetate frame parts are generally milled from sheets of the material.1 Acetate is thermoplastic, so a fitter can use heat to mold and stretch an acetate frame, although too much heat can damage the material.2
More detail
For lens insertion, a cellulose acetate frame is heated only until pliable, with hot air preferred and hot salt or beads acceptable.3 Lenses are edged on size or up to 0.5 mm above the frame size, and a stretched acetate frame shrinks back if plunged in ice water.3 Acetate also absorbs water, which can deform the frame, so acetate frames are uncommon in hot tropical climates.2
Sources (4)
- Brooks and Borish, System for Ophthalmic Dispensing, ch. 1
- Modern Ophthalmic Optics, Appendix A
- Brooks and Borish, System for Ophthalmic Dispensing, ch. 7
- (Brooks, 10/2006, p. 637) Brooks, C. W. 2006, System for Ophthalmic Dispensing, 3rd Edition, Butterworth-Heinemann.
Reviewed October 2026