This is very similar to another question we answered recently, about Magnets Underwater
- and the answer is pretty much the same. The sort of glass you usually see is generally not very magnetic, so you won't feel an effect at all. (I just tried this with a very strong magnet on my window.) However, ordinary glass is magnetic enough to have to be replaced with special glass in some sensitive scientific instruments.
Some glass is made with lots of magnetic atoms, such as cobalt. Usually, these magnetic atoms will not be dense enough to form the sorts of lined-up magnetic domains that are needed to make a permanent magnet. However, there may be enough to get pretty magnetic when they partly line up while a field is applied. Then the glass will actually stick to a magnet. A pane of that type of glass will typically reduce the forces between magnets on opposite sides.
There are even materials which scientists call glasses which are strongly magnetic. Most of these are metals, so they don’t look or feel like window glass. They’re called glass because the atoms in them are frozen but not into a regular crystal pattern, just like in window glass.
(republished on 07/13/06)