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TPott

Flat Port Fogging Issues

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I went underwater yesterday and my lens Port fogged up within a few minutes of being in the water.  I was just snorkeling and the housing was about two feet under the water.  I thought that maybe by leaving the housing in the water to climatize for awhile, the condensation would clear.  Unfortunately after an hour + the condensation/fog didn’t clear.  I swam back to shore, took the unit apart, cleaned the condensation off and tried again. Same issue within a few minutes of entering. 

I’m here in Ontario, Canada. The air temp was 22 degrees Celsius and the water temp was around 18 degrees Celsius. Not a huge temp difference. 

Looking for some suggestions on why this might have happened and what I can do to ensure this doesn’t happen again this fall. 

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Only one way this can happen, the glass falls below the dew point temperature of the air in the housing.  The dew point temperature is set by the relative humidity of the air inside the housing and in turn by the local humidity.  I had a quick look at some points by the Great lakes in Ontario and see the current humidity is over 90% for the station I looked at for a fair bit of the day.  at 22°C and 90% humidity the dew point is about 20.5°C so cooling the glass to 18°C would readily cause fogging. 

Solutions would include using some desiccant packs or closing the housing inside an air conditioned area where the humidity is lower.  You need a fresh desiccant pack - leaving it out of a sealed package would rapidly exhaust its capacity in that sort of humidity.

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On 9/16/2019 at 10:09 AM, ChrisRoss said:

Only one way this can happen, the glass falls below the dew point temperature of the air in the housing.  The dew point temperature is set by the relative humidity of the air inside the housing and in turn by the local humidity.  I had a quick look at some points by the Great lakes in Ontario and see the current humidity is over 90% for the station I looked at for a fair bit of the day.  at 22°C and 90% humidity the dew point is about 20.5°C so cooling the glass to 18°C would readily cause fogging. 

Solutions would include using some desiccant packs or closing the housing inside an air conditioned area where the humidity is lower.  You need a fresh desiccant pack - leaving it out of a sealed package would rapidly exhaust its capacity in that sort of humidity.

Thanks for the suggestions and info Chris!  I've ordered some desiccant packs which should be arriving tomorrow.  I'll put a few inside and see if that helps absorb any moisture.  I have also opened the back of the housing and took off the front port to let everything air out. I'll add some silicone to the o-rings too to get a good fresh seal.  

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4 hours ago, TPott said:

Thanks for the suggestions and info Chris!  I've ordered some desiccant packs which should be arriving tomorrow.  I'll put a few inside and see if that helps absorb any moisture.  I have also opened the back of the housing and took off the front port to let everything air out. I'll add some silicone to the o-rings too to get a good fresh seal.  

Forgive me if I’m teaching granny to suck eggs, I’d just make the point (maybe for a wider audience) that adding silicone to the o-ring doesn’t help make a good seal. O-ring lubricant helps the flexibility of the  o-ring  which should reduce twisting when, eg, tightening or fitting, say, a battery cover or housing back. It has no sealing effect. 

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Pads used for incontinence and feminine hygiene (some of them) can be cut and placed in the housing instead of the desiccant packs.

It is a much cheaper option and they seem to work well. Look for the ones that advertise gel.

K

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