Hey, Your Flash is Hawt …
There are a couple of ways your flash can end up like this. And no matter which way you do it, it sucks to ruin your front fresnel.
Don't Gel Without an Air Gap
Photographic gels are meant to be used near theatrical light sources. So they can handle the heat. Even still, the front lens of your flash can get very hot with repeated cycling -- especially at higher power settings.
Don't believe me? Try this little trick:
Hold a piece of printer paper right next to the front of your flash and set off just one, full-power pop. Now smell the paper. That would be a burning smell. From just one pop. Because not only is your flash heating up, but there is something in front of it keeping the heat from dissipating easily.
Which is also what can happen when you gel. And this is especially compounded when the gel is one that absorbs a lot of light. (Like a full CTB or, say, any dark color.) And if you are working at high levels (above ¼ power) and popping the flash in quick succession, God help you.
So when you gel, leave some space between the flash and the gel for the super-hot air to escape. This helps a lot with cooling. And check in on the gelled flash every now and then to make sure it is not getting really hot up front.
Even When You're Not Gelling
Repeated quick firing of a flash on higher powers can even melt your fresnel without a gel. This is generally not going to be a problem when using AA batteries, because their recycle times become the bottle neck/safety valve in the system.
But when you are using a high-voltage external battery, for instance, you can easily push the flash beyond its design limits. May newer flashes have thermal overload circuits built in, to help keep you from doing something stupid. But some do not. So use care.
All is Not Lost
If you melt a gel, there is hope. If the melted gel is not too fused, try this and cross your fingers. Maybe all is not lost.
But far better to just keep an eye on that flash if popping a lot at high power — especially if you are also gelling.
New to Strobist? Start here | Or jump right to Lighting 101
Connect w/Strobist readers via: Words | Photos
Got a question? Hit me on Twitter: @Strobist
Save Money: Browse MPEX Weekly Strobist Deals