Silica Gel Usage

[MarkH]

IT'S NOT OVER YET!!! .... Actually Ikelite housings have plastic ports, not glass. I think the condensation usually occurs there because the port material is thinner than the body material (which is sort of the same thing as a more-conductive material, like glass). On metal housings, metal conducts heat relatively well so any moisture condenses there instead of on the port (which is glass or plastic). By the time the port loses enough heat, the air is probably dry enough from the "sacrificial" condensation. I've used several film SLRs in Ikelite housings over the years. These cameras have no electronics in them at all (not even a light meter) and condensation still occurs occasionally. It usually happens in summer when the air humidity is relatively high and the water temperature is still cold as usual. I also try to be careful to minimise the water droplets from my hands getting in the housing between dives (when changing film). All it takes is a drop or two evaporating in the housing to really make a mess of the port when it hits cold water.

 

[SwimsWithSharks]

I'm not going to argue with the explanation. The science might be perfect. All I can say is that I have had my Ikelite housing in 46 degree water and 84 degree water with all sorts of variations of topside temps and humidity. No fogging issues at all. As a result, I haven't found the need to use the silica packs.

 

[HowardE]

Hi Joe,

I appreciate your explanation, but it just doesn't sound spot on. As pointed out. Ikelite uses acrylic (plastic) ports as well as housing structure... no glass at all.

I still think that the fogging issue is predominantly with point and shoot cameras and/or video cameras.

I still think the excess heat with point and shoot cameras is from the flash. When you have a point and shoot, you use the flash for either the primary light source or as the trigger for an external strobe. Either way, the flash is going off with almost every shot. Have you ever felt how hot these little flashes are? They're really hot (much hotter than any battery gets). Most P&S cameras also have little housings. Small housing, not a lot of space... air heats up inside really fast.

Video Cameras - in addition to the battery, there is a lot of moving parts. They get pretty warm (much warmer than my DSLR). I do use a silica gel pack in my video housing. I haven't had any fogging, but I have plenty of room in my video housing, so I never worried about it... I just stuck a gel pack in (like I said, they frequently come with shipments to my store)

I'm no science guy, heck I don't have a college degree, but this is what it sounds like to me.

 

[Diver Dennis]

What I do know for sure is that I don't have any problems with my DSLR and howarde doesn't either. As SWS pointed out, he has never had a problem with condensation. I have only seen this once in the tropics but I have to agree with howarde, some P&S cameras, not all, are generating heat from the camera.

 

[joewr]

Folks,

I think we all have enjoyed this topic and regardless of the science or lack thereof, there is one thing we can agree on: if you are having condensation problems, silica gel seems to work just fine.

Actually, there is a second thing we can agree on: we all love diving and photographing nature's wonders...

On that note, I want to thank you all for making life just a bit more fun and interesting for me.

joewr

 

[SwimsWithSharks]

Folks,

I think we all have enjoyed this topic and regardless of the science or lack thereof, there is one thing we can agree on: if you are having condensation problems, silica gel seems to work just fine.

Actually, there is a second thing we can agree on: we all love diving and photographing nature's wonders...

joewr

That's the truth. Doesn't matter much if I have the same camera setup as someone else if that person has fogging issues and I don't. If you fog, throw the packs in. I do wonder about the internal flash comments. Since I use the Ikelite TTL with a P & S, the internal flash isn't used. Just a theory.

 

[Digger54]

.....On metal housings, metal conducts heat relatively well so any moisture condenses there instead of on the port (which is glass or plastic). By the time the port loses enough heat, the air is probably dry enough from the "sacrificial" condensation....

Exactly... makes perfect sense. The rapidly cooling metal housing "scavenges" the water vapor out of the air in the case so there's none left to coat a lens port. In a sense the metal of the housing serves the same purpose as silica gel.

I suppose one good thing about the silica gel is that once it captures the vapor, it holds it so there can't be beads of condensation coalescing and forming puddles dripping or running into electronics.

Some of the wisdom of the housing designers my be that they have the camera mounted so that it does not touch any of the outside walls and they avoid wall condensation being transferred to the body of the camera or the lens.

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

 

[Taxgeek]

I think many of the factors involved in the fogging have been identified.
- conductivity (and hence temperature) of different materials.
- condensed water on camera
- water vapor in air
- relative volume to surface area ratio of different housings
- sacrificial condensation (great term!)
- did I miss anything?

But we still haven't really solved the heating up factor I don't think.

I have another variable to throw in there if Joewr is still interested, regarding fogging patterns in my P&S. I shoot it in video mode, so it is running alot, but no flash. It gets hot. You can feel it being hot when you take it out of the housing. The hottest parts, predictably, are the battery compartment and the LCD (which is warmer than I would have expected). This is a fairly thin acrylic housing, as housings go. It is a uniform thickness everywhere except the lense port, which is glass. The most interesting thing: The housing fogs fastest in certain places consistently. Where? The window right next to the LCD first, then the glass (yes, it's glass on this housing) window in front of the lense. But not by the battery compartment. Factoid: Turn camera off within the housing for awhile during the dive, condensation reduces, sometimes allowing for some more video later in the dive before it fogs again.

Theory: less air circulation space in these areas maybe? The back of the housing is right up against the LCD. Not touching, but close. Likewise, the lense is jammed into a tunnel like cylinder, with rubber glare reduction matting on the sides that sort of seals it in almost.

Problem with theory: Wouldn't the nice hot LCD prevent the air right next to it from getting down to the dew point, even if the cold housing were below the dewpoint? Also, this doesn't explain why the heat seems to increase the condensation (or rather, reducing heat by turning off the camera seems to reduce the condensation).

I've been around and around with this question Joe - it's really irritating to not be able to explain it using physics and chemstry! (Mech E background myself).

Can you make anything out of this extra data? (if you're not thoroughly sick of the topic by now).

 

[Taxgeek]

Digger,
I got a bunch of these from Amazon: (Moisture Munchers). They're expensive, but the big advantage is that they don't have paper corners on them. You'll hear alot of stories about people who are careless one day in inserting their silica pack and the corner of the paper wrapper gets caught in their o-ring, flooding the camera. I likled these because they don't have any corners to get stuck, and you can easily tell when they're "dead" - they turn pink. I just toss them in the bottom of the housing - never had them shift much. I think I would just get cheaper ones next time though!

Moisture Munchers at Amazon

 

[joewr]

I think many of the factors involved in the fogging have been identified.
- conductivity (and hence temperature) of different materials.
- condensed water on camera
- water vapor in air
- relative volume to surface area ratio of different housings
- sacrificial condensation (great term!)
- did I miss anything?

But we still haven't really solved the heating up factor I don't think.

I have another variable to throw in there if Joewr is still interested, regarding fogging patterns in my P&S. I shoot it in video mode, so it is running alot, but no flash. It gets hot. You can feel it being hot when you take it out of the housing. The hottest parts, predictably, are the battery compartment and the LCD (which is warmer than I would have expected). This is a fairly thin acrylic housing, as housings go. It is a uniform thickness everywhere except the lense port, which is glass. The most interesting thing: The housing fogs fastest in certain places consistently. Where? The window right next to the LCD first, then the glass (yes, it's glass on this housing) window in front of the lense. But not by the battery compartment. Factoid: Turn camera off within the housing for awhile during the dive, condensation reduces, sometimes allowing for some more video later in the dive before it fogs again.

Theory: less air circulation space in these areas maybe? The back of the housing is right up against the LCD. Not touching, but close. Likewise, the lense is jammed into a tunnel like cylinder, with rubber glare reduction matting on the sides that sort of seals it in almost.

Problem with theory: Wouldn't the nice hot LCD prevent the air right next to it from getting down to the dew point, even if the cold housing were below the dewpoint? Also, this doesn't explain why the heat seems to increase the condensation (or rather, reducing heat by turning off the camera seems to reduce the condensation).

I've been around and around with this question Joe - it's really irritating to not be able to explain it using physics and chemstry! (Mech E background myself).

Can you make anything out of this extra data? (if you're not thoroughly sick of the topic by now).

Hi,

Well, I am not sick of it, but I cannot, to coin a phrase, see the way forward.

Basically, I think what we need are some controlled experiments, some vital data (heat release, heat-up rates, etc.), and I do not have the time or the resources to conduct them. So, I am being practical...if dessicants such a silica gel or molecular sieves work, then charge ahead.

Of course, the danger of "practical" solutions where the science and engineering are not understood is that one could ruin his camera or housing. That does not seem to be a risk here.

In strict thermodynamic terms, there are some very interesting inconsistencies here and that is what got my attention...and yours, too, it seems. Digger, our patron saint of this thread, got his answer, but I think the chemist in him, too, had lingering questions.

However, I guess I am ready to declare "Victory over the issue" and retreat...

joewr