COATING HOT GLASS WITH LUSTERS
Hot Lusters are formulations for coating hot glass to use the sensible heat to decompose the luster upon application producing the adherent colored film on the substrate. Hot glass (at 800-1200 °F, 425-650 °C) is sprayed right after it is formed. Almost instantaneously, the color is produced. The sprayed ware is subsequently, placed in the annealing oven. This process eliminates some equipments and extra handling required in cold luster decorating. The luster is non-corrosive and the overspray has no effect the metal mount. The film is very minute and the cullet is unaffected.
Equipment. A. Spraying equipment suitable for thin liquid delivered from pressurized cup or container is recommended. Line pressure is 25-50 psi while atomizing air is 10-20 psi. The spraying could be done manually or automatically with a suitable mounting device. Some colors required electrostatic spray equipment. B. The ware should be position to receive the spray and a turntable may be required. Liquid flow, spraying distance and the setting for other spraying variables would be set up by experimentation depending on the size and shape of the ware. C. Suitable exhaust system should be in place to vent overspray and products of decomposition. D. Control equipment may be needed to meet government emission regulations.
Application. The hand glass shop could easily use hot lusters. The ware must be coated as hot as possible immediately after forming. With a spray gun and exhaust system a blown ware could easily be sprayed while still attached to the blowpipe being rotated on a suitable support. Pressed ware would require a spraying turntable. The automated tableware factory could decorate the ware on the glazer after the fire polishing of glass. This is ideal location since the ware is individually mounted and rotating. The ware is sprayed right where it is mounted. The spray gun could be mounted on a mechanism to follow the linear motion of the ware while spraying. The hot luster process is ideally suited for decorating glass blocks. The open half of the block could be sprayed inside before the two sections are fused creating a colored block instead of just plain clear or figured glass. The coating is permanently sealed unaffected by the environment providing an aesthetic and shading value to the block. The flat glass industry could use the hot luster for functional and decorative uses. Coating could be formulated to enhance the reflective properties of the glass. A band of color could be applied on a car windshield before lamination. Applications not critical of atmospheric exposure like bathroom panel and door insert could use hot coated flat glass. Hot lusters have been successfully coated on flint and opal glasses using the colors’ amber, bone, gray, brown, blue, pink, yellow and iridescent.