beside derivication,if you really want to know something you have to get to the root of the problems that cause drivication the halides ,yes the halides are the root cause of derivication[in quartz lamps only]therefore the halides corosive effects on the quartz[similar to the reaction between hot sodium and quartz/glass but happening more slowly]in conclusion eliminate the halides or use only ceramic arctubes.

A factor to consider: from what I have understood, MH also operate at a higher gas pressure and have hotter electrodes to help keep the halide salts vaporized.

BTW....if you eliminate the halide salts, all will be left is a mercury lamp.

Another interesting thing...I've also heard of ceramic MH exploding as well at EOL. I would like to know more about the details of this.

ceramic metal halide lamps dont explode,when the lamps is at eol it just goes out,or the arctube cracks.

Or glows green until the arctube cracks!