Introduction and construction questions

Man in the Moon

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Feb 22, 2009
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Hi everyone!

I've just joined, so want to say hello. My name is Roger, I live in Portland, OR, and I'm building a darkroom. I have a book or two that I'm going from, but I thought it would be nice to see if anyone has some reality-based experiences they could help me with. I've already learned, for example, to paint it white, not black. Glad I did before I started painting!

I'm building in a single-room outbuilding that's about 10' x 14'. The back 10' will be darkroom with the front 4' being workspace (home office) and entry area, and therefore lit and not light-tight. I had designed a traditional U-shaped light trap for entering/exiting the darkroom area, but now I'm wondering if this is too much of a waste of space for the advantages gained. I do not want to use a revolving door because of expense and the fact that I will need to move large objects in and out (the sink, print washers, etc.).

Would I be better off just using a door and hanging a curtain over it? This would mean that every time I wanted to step out to check something in the light I'd have to close everything up and finish make sure all prints were in the fixer before opening the door. With the light trap approach I can step in and out at will without worrying about it. Any opinions?

Also, I'm wanting to install a fan. The outer walls are only 2x4's and there is no ceiling space, so there is only a three inch space in the outside walls. I would like a simple through-the-wall fan with a light-tight louver, but I can't find any that would fit within a three inch wall space. It would also be very hard to use any that required ducting, as ventilation ducting is usually at least 4" and I don't have that much room. I have read some suggestions on here by people that just open the door and run a floor fan every 1/2 hour or so, and I suppose I could do that if worse came to worse, but as I am building this darkroom from scratch (not adapting another room) I'd like to make it as robust and nice as possible, since I have the opportunity and can do anything I want, pretty much. On solution would be a simple louvered vent in the wall that would be exhausted from the positive pressure of the air conditioner/fan that I have installed in the front office portion. But then I'm concerned about air leak. Since it's a small space not heated/cooled by any other area (as a bathroom in a house would be, for example) how do I stop cold air from blasting in through the exhaust system in the winter?

If anyone has experience dealing with these issues I'd be very interesting in hearing any advice. Thanks!

Generally speaking you don't have to go outside to inspect prints. Just
have a work light you can turn on.

Keep your paper in a paper safe and make sure you don't turn on the work
light with undeveloped or unfixed prints about. That shouldn't be difficult.

I don't understand your venting problem or what you mean by only having
a 3-inch space on the walls if you're building this darkroom from scratch.

You can buy nice darkroom vents & fans that are about 12 inches square.
Can't you allow for that in your design?
Regarding your venting, B&H has some products listed. An easy way of creating a light tight vent or air intake is place an opening in your sheet rock in a stud bay at the top of the wall inside the room, then on the other side place and opening at the bottom of the same stud bay, you will need two of these vent openings. Adapt a fan or one of the ready made products. The reason for two vents is the need for makeup air because you will create a vacuum or pressurize the room depending on how you set up your vent, and without the second vent you won't exchange air.

If you are handy, HomeDepot, Lowe's or your local hardware store has stuff that will get the job done.
Generally speaking you don't have to go outside to inspect prints.

Or for any reason really.

I spent years in the darkroom. You won't step away from your film for more than 20 seconds until it's in the fix. Prints aren't much different.

I think the light trap door is a bunch of space to give up, especially if you're trying to conserve.

Good luck!

I agree the revolving/light trap doors take up space and are a pain to get things in and out of. A black curtain or light blocking fabric will do the trick fine.

Again on the vent issue, if the depth of the vent fan is greater than the stud bay, just build a box to gain the extra space out from the wall.
Regarding stepping outside, I guess I have never really worked in my *own* darkroom where there wasn't always someone else's prints in the developer when I needed to look at something. I suppose you're right, Pete. Aside from making sure the paper safe is closed, everything will at least be in the fixer before I'm making a new test print or anything I might need to look at in "daylight".

Regarding the venting, there won't be negative pressure because I have the ac/fan that supplies air from the outside. This alone will create enough positive pressure to push the inside air out. I like the top vent to bottom vent idea, except that the stud bay is full of insulation, and if I leave one empty it defeats the purpose of all the others, and I'd still have to be able to close the vent to keep air from coming back in when I'm not running the ac or fan.

Compur, I'm not talking about the 12x12 dimensions, I'm talking about the fact that the stud bays are only 3.5" deep. If they were standard 6" outside walls this would all be much simpler.

JC1220 - B&H is where I usually get everything, but they no longer carry the Doran A1212 I wanted and now only have 2 fans: a Delta for $200 and a Doran for $250. I'm not paying that plus shipping! I can get the A1212 from Adorama for $125 with free shipping! But the problem is, that is 4" deep and then the 6" pipe comes straight out the back. I would have to do like you suggested and build a box, but since I'd have to do that on the back side (the outside) anyway to keep rain from coming in, that's where I'd do it.

The only remaining problem is that fact that 8 months out of the year around here, it's very cold and I have to heat the space with space heaters. I have two, and they're hard-pressed to keep the space warm when it's cold outside without exchanging the inside air with cold outside air every 4 minutes. I might just have to get the speed control for the fan and run it very low and hope that exchanging all the air every 15 to 20 minutes is sufficient for the chemicals and still slow enough for the heaters to keep up. I'll probably just go to Home Depot or Lowes and get a normal side-venting bathroom fan and deal with the noise.

Gosh, who knew this would be so problematic? Once I get the HVAC issues worked out, the rest of this is cake. Even the plumbing and electrical wasn't this hard! :D The funny thing is that you can find just about anything for your darkroom you can imagine, on Craigslist or Ebay, but never a light-tight darkroom fan. People obviously purchase them or they wouldn't be sold. But I guess when people sell all their darkroom stuff, they don't pull the fans out of the walls!
You might try putting either your vent or your fan in the door with the other
on your wet side. That might make things easier. That's how I've done it.
I would pull your fresh air from the house and exhuast to the outside. Pulling cold air from outside into your darkroom will be a losing battle to stay warm and I wouldn't put the kind of vent I suggested on an outside wall either. You could install some hardwired electric baseboard heaters or a wall mount electric heater, that should keep you plenty warm.

At the depot they sell booster fans for inside ducting, you could run a length of PVC with holes in it or T connections 1 1/2" should be plenty big along the back of your wet area, step it up to a 4 inch pipe where the booster fan is then run that outside to a regular dryer vent with a flapper, just a thought and not very expensive.

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