When studying for exams, you may have been bothered by the harsh glare from a light bulb or tube light. Use a frosted bulb, which reduces glare by giving diffused light.
What is frosting?
Frosting is a chemical process that makes the glass surface uneven. This makes it translucent rather than transparent, so that it scatters light in all directions. The glare and often producing pretty iridescent patterns. Decorative ‘etched-glass’ panels are also made the same way.
A common way to frost glass is by a technique known as ‘bead blasting’. In this, glass beads are fired at the surface to be frosted using a high-pressure device (called a ‘bead gun’). The beads, which are less than a micron in diameter, erode the surface of the glass. Though it may still feel smooth to touch, if you look at it under a microscope, you will see it is not smooth at all. If the nozzle of the bead gun is small enough, interesting patterns can be ‘written’ on the glass.
This is also called etching. Although glass (which is mostly made up of silicon tetroxide) is normally inert, it reacts with hydrofluoric acid to form hydrogen fluorosilicate. The new compound dissolves in water and is washed away. The chemical frosting of glass bulbs was invented and patented by Marvin Pipkin.
When frosting a glass bulb, the inner surface is first coated with wax, which does not react with hydrofluoric acid. Then the area to be frosted is marked and the wax covering it is scraped away. The wax-coated bulb is then filled with hydrofluoric acid. The exposure is timed depending on how deep the frosting must be. When time is up, the acid is washed away with lots of water. The wax is then removed, revealing a translucent pattern against a background of transparent glass.
The chemical frosting of glass bulbs was invented and patented by Marvin Pipkin.