A typical CRT

The first thing to understand is that any TV or computer monitor that is based on a cathode ray tube (CRT) contains a lot of glass (see How TVs Work for a description of CRTs). If you have ever tried picking up a 21-inch (53-cm) monitor or a 25-inch (or larger) TV, you know that all the glass in a large CRT can easily weigh more than 50 pounds (23 kg).

It turns out that the glass in a CRT contains a lot of lead. A big CRT can contain up to 5 pounds (2.2 kilograms) of lead. It is mixed into the glass for two reasons:



optical quality of the glass. Adding a small amount of lead to glass is very common when creating glass for It improves theof the glass. Adding a small amount of lead to glass is very common when creating glass for lenses , and you may have also heard of leaded crystal. Optical quality is especially important at the front of the CRT.

It acts as a shield against radiation generated by the electron gun and electron beam.

The problem with lead is that very small amounts of it cause lead poisoning, so there is a large effort to keep lead out of landfills and incinerators. Communities in the United States have programs to recycle CRTs and television sets.

Here are some interesting links: