Home Brew Humidity Chamber

Whilst there are some nice ex-scientific ones on eBay, I don't seem to have a spare $10k kicking around, so I'm planning on building a humidity chamber (something along the lines of the attached picture), maybe using an old fridge, or possibly something a bit lighter/easier to move.

In the tray in the bottom of the chamber, I plan to use a saturated aqueous solution of Sodium Chloride (since it's easy to obtain), and has a RH of 75.5% at 20C (which seem like a good baseline RH).

Would it be ok to have a series of shelves on which the paper rests - with the sheets on the top shelf at some distance from the tray (if the fridge is tall)? Or, does the paper have to be in close proximity to the tray? I note that Mike Ware recommends:

…a tray with close-fitting lid, in which the paper may be placed face down, over, but not in contact with, a saturated aqueous solution which provides an atmosphere of constant, known relative humidity.

Ideally I'd like to have quite a few shelves with sheets of paper 'ready to go' - so I'd prefer the 'fridge solution' rather than individual closed trays. I'm hoping that wherever the paper is in the chamber (i.e. re-purposed fridge) it will experience the same RH.

If any of you out there have been down this road before me I would be grateful for any tips. Equally, I would love to see some photos of home brewed humidity chambers...

Thanks.

Jim

I'm not sure humidity would be a large issue with modern papers unless you are in a very dry locale. Even so, you probably don't have to be scientifically precise - opting more for a general range of humidity. Not quite sure what your intention is, but since humidification is the issue, have you tried searching for similar concepts related to tobacco and musical instruments? In each case, people have come up with some good home-made humidification solutions you may be able to scale-up to the size you want.

Here are just some ramblings from someone (me) with no understanding of chemistry and only a cursory understanding of the other concepts involved. Take it with a grain of salt, so to speak:

Your chamber could be a larger cooler, or any container that is fairly well sealed (even a plastic cabinet).

Once your chamber is up to the correct Relative Humidity (RH), it should maintain it throughout the container - though opening the door will change things. Once the door is closed, it should reach an equilibrium again.

The cheapest way to do it would be low tech and require monitoring. You will want a decent hygrometer so you can keep an eye on the RH. After some trial and error, you can somewhat control RH by adjusting the orifice of the vessel containing your liquid. The amount of exposed surface area of the liquid can contribute to the amount of humidity; in other words, you would adjust how much of the tray of liquid was covered. This can control the rate of moisture exchange into the air. It needn't be a tray. A jug, jar, or pitcher could also work. Desiccants, scraps of cardboard, etc., can all be used as crude way of maintaining a certain RH.

I think the main thing about a humidor, aside from controlling the humidification, is using a liquid that will not easily contribute to mold/fungus. Many cigar smokers will use distilled water and change it regularly. Some use a solution of propylene glycol in an humidor. It may be possible to use polyethylene glycol, which is the main ingredient in things such as Miralax; I'm thinking cheap, do-it-yourself ideas, and have no idea if this would work.

You could also keep each pack of paper in it's own container (I know you'd prefer not to) and use something like a "Dampit" in each container. I use these in my classical guitars. Another idea is a "Water Pillow." Some people have created homemade humidifiers based on the Water Pillow idea using some form of absorbent kitty litter that has the same materials. For my pipe and cigarette tobacco, I came up with cheap solution using empty Tic Tac containers with a piece of water-soaked antibacterial sponge placed inside.

There are many people more knowledgeable than I on this forum, so if they say I'm wrong, they are most likely correct

I have 3 RH meters and I get 3 readings which are quite far apart. Humidity is rather more vague using the low end equipment.

Just a thought for you to keep in mind. It is much worse IMHO than owning 3 thermometers!

PE

IIRC, a 50-50 mix of Propylene Glycol (as Truzi suggested) and distilled water should result is a RH of 70% (absorbing and releasing humidity as necessary). Perfect for your cubans; whether that's good for paper I don't know. Also good, as I understand, for your Pyrocat.

The foam used by florists for live flowers is a good medium.

Drug stores will generally stock PG; but it can be found in larger quantity (gallon size) and cheaper at farm stores (it's used for cows).

swell

I do think it would be swell, really swell, if you gave us a clue as to just what the devil such a beast is good for, photography-wise. Do you want to raise the humidity, lower it, move it sideways? I do not have a clue.

I just built one for Ziatypes. I bought one of theses.

http://m.ebay.com/itm?itemId=370949473226

They're cheap.

snapguy said:

I do think it would be swell, really swell, if you gave us a clue as to just what the devil such a beast is good for, photography-wise. Do you want to raise the humidity, lower it, move it sideways? I do not have a clue.

Click to expand...

Sorry - thought it was obvious with the Mike Ware reference (i.e. alt-processes).

Just been printing ziatypes recently and would like to control the 'humidity-of-the-paper-variable' as much as possible. Will make life that bit easier if (i.e. when) I hit trouble.

@Mainecoonmaniac - any chance of a photo ? Did you use an old fridge ?

Thanks everyone for the info.

Jim

Never tried it

f8orbust said:

@Mainecoonmaniac - any chance of a photo ? Did you use an old fridge ?

Jim

Click to expand...

Never tried it. My first humidifying chamber was 2 8x10 trays with a bit of water and a rack. Worked ok. My coated Ziatype paper only needed 3 minute in the chamber. As you probably know, I needed to humidify my paper for a good Dmax. With the eBay humidy probe, I'll have data on the humidity and the temp. I've ruined negs by over humidifying my paper.

I didn't know what it was for, and now that the alt process has been revealed, I still don't know much about it. I had thought mass storage in less than ideal locales was the idea.

That said, I've gleaned enough to wonder if doing this with an old refrigerator may not be the best idea. Opening and closing such a large door may make it difficult to keep the RH at the target over short periods of time.

I use three different ESPEC Environmental Chambers at work, and I can tell you that humidity calibrations are always troublesome.

I have a Vaisala humidity sensor that we install in other systems. They have some literature that may be of interest to you:
http://www.vaisala.com/Vaisala Documents/White Papers/lsh-Trouble-with-Humidity.pdf

Page 26 of this one also
http://www.vaisala.com/webinarrecordings/humidity_101_webinar_4_calibration.pdf