This process can produce over 60,000 bulbs per hour per machine, depending on bulb size. If pearl bulbs are required, the interior of the bulb is treated, subsequent to the annealing process, with an etching fluid, comprising mainly hydrofluoric acid, and then washed and dried. Powder coatings are also applied to clear bulbs during lamp making to obscure the filament or for decorative effects; this obviates the environmental problems associated with etching.