housing fog

[e-rider 0]

hi i am trying to stop my housing from fogging up. i have tried desiccant in the housing, should i use an anti fog type spray on it or will this damage the housing. cheers & beers!

[Simon K. 0]

Welcome to Wetpixel e-rider!

 

Maybe you shoulkd Tell Us what kind of a housing and which divecondition you are talking about. Then we may be able to help you.

 

Simon

[jlyle 8]

Yes, welcome to the pond.

 

Fogging inside a housing is caused by moisture and temperature differences. If you don't have any moisture inside the camera/housing, you won't have fogging; it's that simple.

 

The most common source of moisture is condensation inside the camera that originates when a camera is taken from an cold, air-conditioned room, outside into a hot, humid climate. Later, when the camera is in a housing, trapped condensation will fog the colder housing as the camera warms up.

 

When on vacation in hot climates, where your room is air-conditioned, it's a good idea to keep your camera in a plastic bag and let it warm up before taking it out of the bag to take pictures.

 

If you are careful to avoid condensation inside your camera under hot, humid conditions; always load the camera in the housing in an air-conditioned room; and use desiccant packs; you won't have any problems with fogging.

 

PS desiccant packs don't last forever, they can be recharged by heating them carefully in an oven, and then stored in a sealed jar or plastic bag.

Edited January 27, 2007 by jlyle

[drsteve 6]

PS desiccant packs don't last forever, they can be recharged by heating them carefully in an oven, and then stored in a sealed jar or plastic bag.

 

Be careful about recharging desiccant packs in an oven. The calcium carbonate has no problem with the heat, but the paper bags often get brittle. I had a desiccant pack that I had "recharged" rupture in my housing covering everything with a snow of calcium carbonate. Fortunately it wasn't that hard to clean up and none of it got in the lenses.

 

I have had better luck recharging them in a microwave oven.

[jlyle 8]

Be careful about recharging desiccant packs in an oven. The calcium carbonate has no problem with the heat, but the paper bags often get brittle. I had a desiccant pack that I had "recharged" rupture in my housing covering everything with a snow of calcium carbonate. Fortunately it wasn't that hard to clean up and none of it got in the lenses.

 

I have had better luck recharging them in a microwave oven.

 

Hence the "carefully." To be more specific, a couple of hours on a cookie sheet in a 200 degree oven will do the trick. Let them cool, then place into a zip-lock bag and then put that bag inside another bag. You can get 2g desiccant packs with color indicators from preservesmart.com.

[e-rider 0]

Welcome to Wetpixel e-rider!

 

Maybe you should Tell Us what kind of a housing and which dive condition you are talking about. Then we may be able to help you.

 

Simon

 

hi Simon it is a sea & sea 8000dx type housing, which i believe is made out of polypropylene. the local conditions are about 70-80% humidity & cold water temp of about 21deg C (sorry to those who brave temperatures below this) i have just changed the old desiccant bag for a new one as maybe it was to old.

cheers & beers, Gav.

[e-rider 0]

thank you all, it was the desiccant bag that went off. i have now done 2 dives with a new bag inside. no problem! i don't know about reuseing them as i picked up 100 from judy on ebay for $10. thank you all again.

[belizediversity 0]

Just to add that another way to "recharge" the dessicant is to nuke it in the microwave for a few minutes, same cautions apply as regards rupturing the bag.

 

I had a mysterious bout of fogging a few months ago. It wasn't a/c (coz I don't have any) but I traced it down to cool morning temps (when I set up) warming up to a hot midday. The fogging always occured on the 2nd or 3rd dive of the day. I started putting the camera housing in an ice box full of water to cut down on the temperature changes duiring the surface interval and that seemed to sort it out.

[drafahl 0]

In addition to everything that has been said about taking care when loading your camera to avoid changes in temperature, you MUST keep a towel over any clear housing when out in the sun. This means taking special care to see your camera housing is covered by a towel (wet is better so that it doesn't fly off) when set it in the bow of the tender boat.

 

Jack and Sue

www.jackandsuedrafahl.com

[Taxgeek 0]

Hi Jack and Sue.

Your point brings up a question that people seem to wrestle with on and off, and we can never figure out the scientific explanation for it. Why does adding heat to the air/camera/water vapor already inside the housing have an effect on fogging? This happens when a P&S heats up during use too, right?

 

Adding heat should reduce the absolute humidity, causing less fog, because air can hold more water without "dewing" at higher temperatures than at low temperatures.

 

I've just never been able to figure out why adding heat causes less fog, rather than more, and yet, it clearly does.

 

Got any theories?

Thanks!

Susan

 

 

In addition to everything that has been said about taking care when loading your camera to avoid changes in temperature, you MUST keep a towel over any clear housing when out in the sun. This means taking special care to see your camera housing is covered by a towel (wet is better so that it doesn't fly off) when set it in the bow of the tender boat.

 

Jack and Sue

www.jackandsuedrafahl.com

[jlyle 8]

Hi Jack and Sue.

Your point brings up a question that people seem to wrestle with on and off, and we can never figure out the scientific explanation for it. Why does adding heat to the air/camera/water vapor already inside the housing have an effect on fogging? This happens when a P&S heats up during use too, right?

 

Adding heat should reduce the absolute humidity, causing less fog, because air can hold more water without "dewing" at higher temperatures than at low temperatures.

 

I've just never been able to figure out why adding heat causes less fog, rather than more, and yet, it clearly does.

 

Got any theories?

Thanks!

Susan

 

Susan,

 

It's a matter of distillation & temperature differences. When one part of the housing heats up, moisture is vaporized; this moisture then condenses on a cooler part of the housing. That's why condensation inside the camera is so insidious - as the camera warms up, the condensation is driven off and fogs the colder housing. It isn't the heat, it's the temperature gradient.

 

Jim

Edited January 30, 2007 by jlyle

[Taxgeek 0]

Thanks Jim.

So let's see if I understand this. You're saying there is significant condensation on/in the camera that we should be taking into account, in addition to the moisture in the air. So when the camera or air inside the housing warm up, it vaporizes this moisture, which then condenses on the cooler housing either right then or later on.

 

Does that sound about right?

Susan

 

Susan,

 

It's a matter of distillation & temperature differences. When one part of the housing heats up, moisture is vaporized; this moisture then condenses on a cooler part of the housing. That's why condensation inside the camera is so insidious - as the camera warms up, the condensation is driven off and fogs the colder housing. It isn't the heat, it's the temperature gradient.

 

Jim

[jlyle 8]

Thanks Jim.

So let's see if I understand this. You're saying there is significant condensation on/in the camera that we should be taking into account, in addition to the moisture in the air. So when the camera or air inside the housing warm up, it vaporizes this moisture, which then condenses on the cooler housing either right then or later on.

 

Does that sound about right?

Susan

 

Yes. If you take a sealed glass tube with humid air inside and heat one end with a flame, you will get condensation (fogging) in the cold end. Bottom line: keep as much moisture/humidity out of your camera & housing as possible; use desiccant packs; and keep the rig out of the sun.

[belizediversity 0]

The other thing about fogging in housings is that the glass of the port transmits heat better than the plastic of the housing body and so cools the moisture laden air quicker causing the inside of the port to fog up. Isn't physics frustrating at times, you could continue shooting if only the back plate of the housing fogged but the glass port is a pretty important part of getting good imagery!!

 

Defogs for masks will not work because they are keeping your mask clear by a different mechanism. Defogs (including spit) are mild detergents which allow water to "stick" to glass. By applying a defog to a mask and then rinsing it you are making a thin film of water stick to the inside of the glass of the mask which you look through. If the mask dries before use or there are any greasy patches stopping the defog from working then you will get a fogged mask. Therefore if you spray defog or (God forbid) spit into the port of your housing port you would have to rinse out the port and then keep the inside of it wet inorder for the port to be kept clear of fog. This rather negates the whole purpose of the housing, to keep the camera dry.

 

Best to follow the advice above, try to assemble the housing in a dry environment and keep it form heating up between dives.

[divegypsy 23]

I'd like to suggest a different solution to the problem of condensation fog forming inside housing. I have used it and generally had decent results with it. As everyone has mentioned so far, the basis of the problem is moisture in the air inside the housing and a change in temperatures that causes the condensation.

 

Since the problem is caused by moisture in the air inside the housing, the solution is to eliminate the moisture.

 

My solution to this problem is to attach an air blower to my regulator's inflator hose and blow scuba tank air (which should contain no moisture at all) into the housing through a small crack (created by positioning the two housing halves in an almost closed position) for a few seconds before closing it. This displaces most or all of the normally moist atmospheric air with dry scuba air. And greatly reduces the chance of any condensation.

 

divegypsy

[jlyle 8]

I'd like to suggest a different solution to the problem of condensation fog forming inside housing. I have used it and generally had decent results with it. As everyone has mentioned so far, the basis of the problem is moisture in the air inside the housing and a change in temperatures that causes the condensation.

 

Since the problem is caused by moisture in the air inside the housing, the solution is to eliminate the moisture.

 

My solution to this problem is to attach an air blower to my regulator's inflator hose and blow scuba tank air (which should contain no moisture at all) into the housing through a small crack (created by positioning the two housing halves in an almost closed position) for a few seconds before closing it. This displaces most or all of the normally moist atmospheric air with dry scuba air. And greatly reduces the chance of any condensation.

 

divegypsy

 

That's a great option, especially on a boat if you open the housing for any reason. They make an adapter that fits on the end of a LP inflator hose that you can use to blow out the housing.

 

Another option is to use a hair dryer in your A/C room - the warm/dry air will also reduce moisture.

[marksm 0]

As mentioned previously, I too agree that blowing dry scuba air into the enclosure is a great solution and one I employ whenever I have had to open a housing on the deck. It has worked every time. Just recently, I had to open the housing on a dive deck in very warm moist air and then jump into 42 degree water. Not a problem using this technique.

 

This has been my experience: Assuming moisture content does not change in a sealed housing, then you need to seal the housing with as low moisture as possible. If you can seal your housing in an air conditioned room with low humidity, then it should not matter the outside temp or humidity. If there was no fogging of the lens inside the room, and the water temperature is equal to or higher then the room temp then I don't think it is possible to fog. Colder air can hold less moisture so as a housing cools moisture will begin to condensate once the housing air reaches a temperature that it can no longer hold the moisture.

 

Now here is something I'm not sure of...Does the speed or the temperature delta speed affect how condensation occurs? If that were true then covering the housing would lesson the difference in housing vs water temperature. And here is another unknown for me: I use to see guys put their housings in ice chests? Why if the moisture stays the same in the housing? Now I have had a fogged lens clear up after a while but I have always attributed this to rising temps in the housing due to the camera heating it up. And the higher temps allowed more moisture content in the air and thus it evaporated from the condensed lens.

 

Now imagine if there were something that cooled faster then the port that protruded inside the housing such as a piece of steel or thin conductive material. I wonder if this could be used as the "moisture magnet" instead of the port and it pulled the moisture out before it condensed on the port or lens. That would be nice as long as someone could prevent a drip of water from falling on the camera. Well there is my million dollar idea...someone send me a check

 

Mark