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  1. #11
    Jim Noel's Avatar
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    If the RH ever got to 50% in my darkroom I would be adding to it with perspiration. It is usually in the 20-30% range, but can get down to 10% or less in certain weather conditions.

    I normally do not re-humidify, but when the RH is extremely low, I do so over a small electric skillet with water almost simmering. Of course this also raises the RH in the general room atmosphere.
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  2. #12

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    Quote Originally Posted by Joe Lipka
    You are coating the smooth side of the paper of course...
    Hi, Joe:

    Yes, I am coating on the smooth side.

    Anyway, one other factor I'm thinking about may be playing a role with my problem. My basement darkroom temperature is a rather chilly 62 - 64 deg. F. Perhaps this is inhibiting the absorption/evaporation of sensitizer despite the RH being 55%. I notice that after any of my coats are applied, it takes about 10 min. before the "wet look" goes to satiny/velvet/matte look when I start to blow dry it. Most sources I've looked at say it usually takes 5 min. or less to reach the satin look so maybe my cold darkroom temp. is playing a role here. I always thought the RH determines the rate of evaporation but maybe temperature plays an important role also. Any weatherman (weatherperson) or physics person out there who can comment on this?

    Thanks for all your input--It's nice to hear what other people are doing about what I believe is an overlooked problem with hand coating.

    Bob

  3. #13
    Kerik's Avatar
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    Bob,

    I would definitely try to warm up your darkroom space a bit. Or, coat the paper elsewhere in the house where it is warmer.
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  4. #14

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    Quote Originally Posted by Bob Fukura
    Hi, Joe:

    I always thought the RH determines the rate of evaporation but maybe temperature plays an important role also. Any weatherman (weatherperson) or physics person out there who can comment on this?

    Bob

    No, but I aced a course in meterology 25 years ago. I've just been dying to use it!

    Yes, temperature will have such an effect. Cooler air cannot hold as much moisture as warm air, (hence the relative in relative humidity) and will slow evaporation.


    Wayne

  5. #15

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    Kerik:

    I'm definitely going to warm up my darkroom--I think this will help with the coating. Thanks again for your help!


    Wayne:

    I'm thinking both the RH and the ambient temperature play a role here. Interestingly, in my search for the relationship, I found this helpful site:
    http://www.shorstmeyer.com/wxfaqs/hu.../humidity.html
    Thanks for your input!

    Bob

  6. #16
    Michael Slade's Avatar
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    I coat my papers in the main floor of my home, let them dry there then take them into the basement where I have my plate-burner. The basement is unheated and uninsulated and is a constant 56 degrees. I have wondered if temperature affects the coating/drying process...guess we have a good answer now.

    BTW, I do the processing in the main level of the home too.
    Michael Slade

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