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  • Dark Room Humidity

    Hi Colin!! What is the ideal humidity level for a dark room? I generally say zero to low humidity but have never actually tracked the details! What's your opinion? Thank you!

  • #2
    Hi Jamie!

    If you have your screens drying or being stored in an open room, like many smaller shops do, you want the whole room to be between 30% and 40% relative humidity. The best way to test for this is using a Hygrometer. You can pick one of these up at Home Depot or Lowes as well as online. They are anywhere between $20 and $40 depending.

    Within that small space you will also want to have a couple of box fans to move the air around and - ideally (please go get one) - a dehumidifier. You want to set the dehumidifier to 35% and let it run continuously if you have any screens in there that are coated or drying.

    I like to keep this room no hotter than 80-85 degrees and no cooler than the low 60's.

    If you happen to have a screen storage box - you want the same level of humidity in there that is stated above. If you cant fit a dehumidifier within that box, I recommend getting a pellet dehumidifier and placing a hygrometer in that box so you know the condition of your emulsion before exposing your screens.

    In the end, this is about keeping the proper moisture levels within your coated screen. When your screen is at the proper dryness your screens expose better, the stencil is more durable, and your image rinses out like it should.

    If your emulsion is too wet or "gummy" you will not be able to spray out fine details or get clean edges to your stencil. You will also see decrease stencil durability on press.

    If your emulsion is to dry, the stencil can actually be too brittle and will blast away in chunks when spraying out the image. You will also see decreased stencil strength on press.


    • Leinbacher
      Leinbacher commented
      Editing a comment
      This is fantastic info Colin, thank you!!! Purchasing my dehumidifier was a major game changer in the quality of my screens. I know this info will help a bunch of people perfect their screen game so I'm sharing on the Band Page. Thank you so much!!

  • #3
    HI Collin, I have maybe kind of same question. We used to have a very small darkroom where we stored screens and also washout for exposed screens - so kind of risk with humidity but the small electricity ran all the day so after washout the humidity went donwn to 30%. Now we moved the dark room into a bigger space, same temperature, buyed new humidified that shows below 30% all day but our screens now can´t run over 1 000 prints - with the same emulsion that we used before. So we tried different emulsions, different times on LED exposure unit... nothing happen and still we do the same. Same mesh (NBC from Japan), same degreaser.... Do you have such an idea what can affect the "gummy" emulsion (probably) that don´t stick to the mesh correctly?


    • #4
      Ludweek: Are you using fans to circulate the air? Can you upload a couple pics of the dark room? I assume you have a De-humidifier?

      How many prints were you able to get before?

      There are several possibilities as to why the reduced impression count. The question is: where exactly in the new space, did changes happen compared to the old space.


      • #5
        Using fan but not all the day, as I load wet screens to dry I turn fan off for a while to avoid small parts gettig into a screen, as it´s a bit dry I turn the fan on again. And yes, we have strong de-humidifier that sucks everyday like 4 liter and keeps it under 30% We were able to print in thousands before but now 1 000 pcs is sucess. I will make some pics of the new space. The main thing that is not similar as the old smaller space is that we put screew compressor into a new space - it runs our squeegees on automatic but also produces hot-air that we use to dry screens. As I talked with the Atlas Copco (brand of compressor) guy there should be no "dirt" in the hot air, this air is just taken from the room - cool the comperssor and goes out, this was my biggest fear, but it should be not...


        • #6
          What emulsion are you using? Any Diazo? How hot is this air?


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