Baking desiccant plug: cool-down

[rogerg]

Something I've pondered regarding baking my ST7's desiccant plug.... I've baked it several times over it's 6 odd year life time. Each time I wonder how best to cool the plug.

I put the plug in the oven, bake it for the required time (4 hours!!). After that time I turn off the oven, but the plug is obviously still hot. So, it must cool before I can put the rubber o-ring back on and re-attach it to the camera.

Once baked I leave the plug in the oven, closed, cooling. It takes a while to cool, let's say an hour later I check it and it's cool for me to put back in the camera. During that cooling down period, surely the plug has soaked up a lot of moisture which means it's "charge" is now less?

The plug would cool much quicker if I put it out on the bench, but surely if it were out in the open it would quickly soak up a lot of humidity?

So.... I wonder if anyone knows how quickly the plug soak's up moisture, as to what the best procedure is: quick cool down on the bench, longer cool down in the oven, etc?

Roger.

[Omaroo]

Roger - I do the same thing. I choose to leave the plug in the oven as it cools, because I truly suspect that the closed oven would maintain a very, very dry atmosphere inside as the trapped air cools.

I used to take out the hot (200C) plug after the 4 hours and wrap it quickly and loosly in aluminium foil - and pop that into a sealed ziplock until cool. I now don't see the point of it.

[AstralTraveller]

If it were me I'd do it at work in a dessicator but I think the oven sounds like the best choice. Otherwise any small closed container would suffice.

Does the dessicant have an indicator which changes colour as it absorbs water? They could be blue or orange when dry.

[Omaroo]

Not that you'd easily see - it's buried inside a cylindrical container with a wire mesh across the entrance. Some after-market versions make it accessible, as you're meant to replace the dessicant itself.

[rogerg]

Thanks for the replies... at least I'm not alone in how I do it and wondering the best way.

Some kind of indication of "moisture saturation" would be nice, as the whole "I think it needs baking" and "I think it's baked enough" is rather mysterious/ambiguous apart from fogging creeping in during exposures indicating saturation while in the camera.

[Terry B]

I don't think it really matters.
It doesn't soak moisture in that quickly.
I take mine out of the oven and put it on the bench on a metal tray. This conducts the heat away quickly. 10 minutes later it is cool enough and I put it in the camera. I find it lasts about a year before I ned to do it again.

[JohnG]

Likewise, I also run the camera (ST4000XCM) at 0.00c for a while before dropping the temp to my normal operating temp of around -20c.

Cheers

[Dennis]

Have a look at the Farpoint SBIG Replacement Desiccant Plug (http://www.farpointastro.com/desiccant.php).

This desiccant plug system replaces the original desiccant cartridge, converting it to a no-bake, field serviceable system. Desiccant is in the form of 3-gram disposable pouches.

Ron at Sirius Optics (http://www.sirius-optics.com.au/farpoint.html)lists them on his webpage.

Cheers

Dennis

[rogerg]

Interesting idea Dennis. Not worth me doing with my ST7 (cost vs benefit on the old camera) but something to keep in mind as an option.