Request information on humidor specifics

[Ralf]

Can someone recommend a site or document where I can learn all about humidors? Info like materials used, shapes, craft, dimensions, hydrometers or hygrometers (however its written). Any links will be appreciated.

I have always been curious on these matters and I have asked myself if there is a industry standard, or comparison point, when buying a humidor.

Finally, what characteristics must a humidor have to be considered a "good humidor"?

Thanx all
Rx.