Subject: Why will my strong magnet (4000 gauss) damage my TV screen?

I opened up my (now defunct) computer hard-disk and plucked out the cool 0.4 
Tesla magnet - i've been having fun with it in the School Lab with the CRT (in 
the electron diffraction experiment) - i take the magnet close to the ZnS 
screen, the electrons sway - and voila! i have lovely patterns reminiscent of 
aurorae.

Problem is, i wish to try out the above with my TV's CRT - i did it for 2 
seconds and the patterns were lovely!

I read that i will damage my TV if i keep the magnet close too long. Why 
exactly?

Re: Why will my strong magnet (4000 gauss) damage my TV screen?