Silica Gel Usage

[bladephotog]

My DSLR in my Ike housing will sometimes fog in our cold water. So I always use Moisture Munchers. Even then, sometimes I get a little condensation but not much. And I do like the Moisture Munchers. I can fit two or three of the big ones under the camera body and they stay there.

 

[joewr]

Thanks all for the variety of input. I've not gotten my housing wet yet and am itching for the opportunity.

Digger,

As they say somewhat south of the Mason-Dixon Line, "Git 'er done!"

And be sure to post your photos. And be sure to send me a PM so that I know you have them posted. And be sure...well, just be sure...

joewr

 

[dave4868]

Great thread! Why stop now....

I may have missed it, but did anyone mention pre-cooling the housing/camera before the dive?

I agree with many who may have mentioned factors of dewpoint, the increase in relative humidity (and dewpoint) caused by the heating of the camera by electronic operation and/or solar gain, and the faster cooling of the lens port creating a relative "moisture magnet" on which the water vapor will condense.

I've got an Olympus 4040 and Ikelite housing and despite my typical cold water dives (below 50 degrees), it rarely fogs up now.

FWIW, here's what I'm doing.

On days when the dew point is low, I've been able to get away with doing nothing, but don't take the chance usually. Typically, I'll put 3 small desiccant packs in before the dive.

For the days when dew point is moderate, I just put 3 small desiccant packs in the housing with the camera a few hours before the dive.

Worst case is in early summer on a day with high dewpoint, like 60 degrees, but cold water, such as 45 degrees. If the dew point is 60 degrees, I know chilling my camera to 45 degrees during the dive is a going to cause condensation, unless I take steps to dry out the air in the housing and in the camera.

The day before such a day, I'll put a dozen or so desiccant packs in a plastic bag with my camera. I'll also put a few in the housing to dry out the foam rubber in the lens tube area. Several days of this drying is even better, of course.

A few hours before the dive, I'll remove all the desiccants and replace them with the usual 3 fresh packs when I mount the camera in the housing.

By the way, to avoid putting a "set" into the shape of the o-rings, I lightly close the housing back with doubled rubber bands, rather than leave it latched for many hours. Just need to remember to latch it down before the dive. :11:

Prior to the dive, I avoid leaving the camera/housing exposed to the sun. I think there's a greater chance of fogging when heat has caused the materials to release moisture. I read somewhere that even the plastics will release a small amount of moisture.

Anyone know if that's true?

Between dives, I soak the unit in cool fresh water in a cooler.

If I need to open the housing between dives on one of those days with the worst circumstances of high dew point and low water temp, it will help to first let the camera come to ambient temperature before exposing it to the humid air. Then I make the exposure brief. I've even seen guys use scuba tank air to fill the housing before closing it back up. Makes sense. With an air nozzle, of course.... don't want to hear of anyone blasting salt spray on their electronics....

Once closed up, the unit goes back into the cool water bath.

On the worst day for us, the dewpoint might be 65 degrees and water temp, below the thermocline, might be 43 degrees.

On those days, if the housing has been opened up and exposed to the humid air, an even colder soak may be needed to prevent fogging.

I'll chill the water bath with ice, then immerse most of the housing, but not the lens port. The housing will chill down nicely before the next dive and be less likely to have fogging of the port.

As someone pointed out, this causes the housing interior and contents to take up some of the water vapor and lower the absolute humidity.

Since the lens port isn't cooled during the ice water soak, condensation won't be occuring there.

I may have the physics wrong, and it may sound like "crazy talk", but this ice bath really works. Try it.

You should still be able to get above-water shots just prior to the dive, too, because the lens port won't get external condensation either. You'll have to wipe fog off the back of the housing to see your LCD, though!

Dave C

 

[joewr]

Hi, Dave,

I don't mean to abandon you, but I think we have gone about as far as we can go without doing some serious experimentation and gathering some very basic data. I have neither the time nor inclination to do this and so I am willing to take the easy way out: if a dessicant works for you, by all means use it.

There are lots of things in this life that we use without the foggiest idea as to science/engineering involved...so I guess we can do that here.

It was fun, though, and I enjoyed reading your post.

Have fun diving and photographing....

joewr

 

[dave4868]

joewr wrote politely:

I don't mean to abandon you, but I think we have gone about as far as we can go without doing some serious experimentation and gathering some very basic data. I have neither the time nor inclination to do this and so I am willing to take the easy way out: if a dessicant works for you, by all means use it.

Perfectly understandable.

If this winter gets really oppressive, I'll start another thread about the informal tests I performed on rejuvenating silica gel packs, the best oven temps and cooking times, the decrease in water weight after heating, and the desiccant packs' effectiveness in lowering relative humidity for given volumes of air....

Sorry, that might have sounded threatening.... I won't do it until the "White Death" of being snowbound drives me to it!

There are lots of things in this life that we use without the foggiest idea as to science/engineering involved...so I guess we can do that here.

It was fun, though, and I enjoyed reading your post.

Have fun diving and photographing....

Thanks. I'm just a tinkering fool and empirical observations are my primary guide, for want of analytical ability, no doubt.

Catch you on the flipside!

Now, if everyone will indulge me, I'd like to try to address the original poster's questions... I'll be brief.

I know what the silica gel does, I use some larger "rechargable" packets of it in a gun safe at home, but I am unsure of how to best apply it in underwater photography.

Do most keep silica gel in the housing during a dive?

I use them on every dive, although I think I could do without them when the weather isn't real humid.

I'll have to try those rechargeable packs, especially if they can be done in the microwave.

I have several hundred of the regular kind that I bake and then seal in plastic bags, 20 per bag. The batch will last me two or three years, if sealed well, retaining most of their fresh capacity, for a decent shelf-life.

Where do you put it in the housing? I might have enough space between the tray and housing bottom if the packet is thin and small enough.

My Ikelite housing has room under the camera mount, and elsewhere. I use three small packets, each about 1 1/2 x 1 x 3/16 inch in size.

What do you do to avoid it moving and interfering with the operation of controls?

They are lightly trapped in place by the housing and camera. My housing has several areas that will accomodate and box them in.

Is it likely to produce any dust if it flops around in the housing that could coat a lens and reduce the sharpness of photos?

I think it's possible and worth avoiding. I've had no problems with dust or with the packets moving around, though.

If, like me, you're contending with extremes of high ambient humidity and low water temps, read my other post about pre-cooling the rig in a water bath. That helps greatly.

If the housing has to be opened between dives, injecting scuba air helps, too.

HTH. Thanks for helping me pass some of winter doldrums!

Dave C