I've never had any lamps explode from exposure to the elements....
I think you missed the
point of what Mike was saying about exploding lamps. What makes lamps (or reflectors for that matter) explode isn't as simple as water + lamp = explode. What would cause a lamp to explode would be the rapid contraction that happens when hot things (a lamp that's been running for a while) come in contact with relatively cold things (snow that melted down the
barrel, that rain storm that just started,
etc...). If you've never decided to see what happens when you take a spray
bottle full of water and spray a light
bulb that's been on for a while, I assure you it does in fact blow up.
What the lights in your outdoor
venue are probably experiencing is more a situation where any moisture in the
fixture is more of less the same temperature as the lamp when you turn it on initially, it will warm with the lamp as it is used, and after use cool slowly with the rest of everything in the
fixture. No instantaneous change in temperature, no rapid contraction, no explosion. The fact that the water and the lamp don't change temperatures at the same rate is probably detrimental to your lamp life but that's not what we're talking about right now.
As far as how I would project a
gobo outside for an extended period of time. I'd probably
build something to
cover the actual
fixture with a hole in it that I would focus the light through and let the light emitted by the
unit melt any snow
build up that would occur. The tempest stuff is an all out way to go but probably a
bit expensive for a light meant to spread
holiday cheer.
EDIT: After re-reading ship's post I decided to mention that I don't think that in most situations exploding lamps would be a concern. But if you are expecting any kind of downpour or blizzard like conditions I'd turn your lights off. No one will be appreciating them anyway cause of the crappy weather and it will protect you from this possibility.