Dry cabinet plan

Anirudha Ambekar · Sep 27, 2018

Hi!
I now live in a very hot and humid part of the world.
This means all the optics that I have is at risk of fungal growth.
I have been using a small airtight plastic boxes and silica gel for individual equipment/ films which became cumbersome.
Plus I couldn't find any plastic airtight box long enough to fit my ED80 scope tube (~ 50 cm long).
With the commercial dry cabinets either too small or too pricey, I am now entertaining the possibility of a DIY route.
And the idea is to use a broken refrigerator as an airtight cabinet with silica gel and a hygrometer.
The idea seems simple enough but I couldn't find anyone who has done this.
I am wondering if its either not feasible or outright bad idea!?
Any inputs?

Mick Fagan · Sep 27, 2018

I would suggest if you are handy, you can build your own reasonably cheaply.

One dry cabinet I helped a friend build around 20 years ago, was pretty simple. Essentially a two shelf cabinet with a glass door that was held shut with a clasp arrangement and in-between the glass and the cabinet with some foam to seal the inside from the outside.

The heating came from a tungsten 40W (I think) light globe. The air inside was circulated with an old computer fan that had been really cleaned with compressed air, this was an overkill, but I know my friend left that fan in for about 5 years. I'm not too sure if he replaced it when it died, but I know he used it for a couple of months before he found out it was not running. With, as I understand it, no ill effect to his equipment.

To prime his cabinet he used a hair dryer to dry out the inside getting it quite warm and dry, then he sealed it up and switched it on.

This is not ideal as one really should have a de-humidifier that expels moist air externally, but it did work. He lived in Darwin, which is really bad during the wet season; condensation literally runs down the walls of houses then.

Kino · Sep 27, 2018

Airtight box and a 750 gram silica gel canister that can be regenerated by a few hours in an oven.

http://www.jpscorner.com/silica-gel-humidity-control.html

I haven't done it yet, but am contemplating using a pure copper heat sink with a high power LED for interior lighting. This will serve two purposes;

1. To illuminate the interior for display.
2. Fungal control from the fumes of the copper heat sink; copper is a very good fungicide.

Any one of these should work, and if you use a CPU version, the fan can supply re-circulating air currents.

https://www.google.com/search?clien...-wiz-img.......0j0i67j0i8i30j0i24.Eq3gQD05Czw

And to the inevitable alarmists who think everything is a toxin just waiting to kill them:

https://www.cdc.gov/niosh/idlh/1317380.html

Of course, some people can be allergic to copper, but my advice is; if you are, don't use it.

REAndy · Sep 27, 2018

As a desiccant, silica gel is available bulk/loose. You can get it with an indicator. I believe it turns pink when it needs to be regenerated, which you can do in your oven. Get enough gel for 2, that way you always have one in the dry cabinet while the other one is being regenerated. Also check out the boating/yacht websites, as they sell desiccant devices. As you can imagine on a boat this can be an issue.

A quick check on one of the major online retailers (you know that jungle place in South America? Same name). Anyway, they sell a plastic jug, 1 gallon for about $35. The one I saw, is blue, and turns pink when exhausted (needs regenerated). Can be regenerated many many times.)
You could pour half of it in plastic containers (what I like to call "Grandma's Tupperware") like an empty cottage cheese container. Poke holes in the lid, or better yet, cut out the center of the lid and affix a screen/mesh to the top. 1/2 gallon would probably fill several of these containers so you could place them on different shelves in the dry cabinet.

Good luck and let us know how it turns out, and what you decided to use.

Rick A · Sep 27, 2018

Um.... store your gear in a sealed room with a dehumidifier. Use a bit of weather stripping to seal around the door and windows.

jim10219 · Sep 27, 2018

Yeah, I'd just throw it in a closet with a small dehumidifier. That gives you more room and better circulation.

I don't trust the silica gel. They absorb AND release water vapor. I had an air tight safe with silica gel packets in it where I kept all of my important documents. It worked well for a couple of years, and I occasionally remembered to regenerate the silica gel packets. But apparently one day I opened it up on a particularly humid day and closed it back up, not thinking about it. When I checked it again about a year later, everything was covered in mold.

Anirudha Ambekar · Sep 28, 2018

Hi!

Mick Fagan said:
I would suggest if you are handy, you can build your own reasonably cheaply.....

So the Idea is to keep the temperature in the cabinet high enough to avoid condensation. Correct?

Kino said:
Airtight box and a 750 gram silica gel canister that can be regenerated by a few hours in an oven...
...I haven't done it yet, but am contemplating using a pure copper heat sink with a high power LED for interior lighting.....

And Kino's idea combines desiccants with heating.

jim10219 said:
Yeah, I'd just throw it in a closet with a small dehumidifier.....

I am sure dehumidifiers also use silica gel or hygrospcopic material of some kind. I was under the impression that the re-release of moisture from these materials happens only when they are heated to 60 deg C or more.

REAndy said:
...A quick check on one of the major online retailers (you know that jungle place in South America? Same name)...

ha! Amazon!! I'll certainly post about my progress.

I guess my worry was if a refrigerator would work as a dry box/ airtight container. But I see that I can make a cabinet with other materials and still make it airtight (enough) for the purpose.

Rick A · Sep 28, 2018

Buy something like this and put your things in a small room or enclosure with it.
https://express.google.com/u/0/prod...NcleeTF_hJj3vK1Erga9v2_kjf_dPUlRoCv2cQAvD_BwE

Sirius Glass · Sep 28, 2018

Also consider using a dehumidifier to keep the cabinet dry.

John Koehrer · Sep 29, 2018

Mick Fagan said:
I would suggest if you are handy, you can build your own reasonably cheaply.

One dry cabinet I helped a friend build around 20 years ago, was pretty simple. Essentially a two shelf cabinet with a glass door that was held shut with a clasp arrangement and in-between the glass and the cabinet with some foam to seal the inside from the outside.

The heating came from a tungsten 40W (I think) light globe. The air inside was circulated with an old computer fan that had been really cleaned with compressed air, this was an overkill, but I know my friend left that fan in for about 5 years. I'm not too sure if he replaced it when it died, but I know he used it for a couple of months before he found out it was not running. With, as I understand it, no ill effect to his equipment.

To prime his cabinet he used a hair dryer to dry out the inside getting it quite warm and dry, then he sealed it up and switched it on.

This is not ideal as one really should have a de-humidifier that expels moist air externally, but it did work. He lived in Darwin, which is really bad during the wet season; condensation literally runs down the walls of houses then.

We used a similar method in VietNam although the lockers were thin wood, the light bulb worked fine to keep things dry.
We used them for camera stuff but as a wall locker. I was on the air base at BienHoa not trying to carry these in the field
had a cushy life compared to most of the guys that were there.

Mike Bates · Sep 29, 2018

Heating an enclosed space doesn't remove moisture. It does lower the relative humidity, but that's only a measure of the amount of moisture the air is capable of holding. Warm air is capable of holding more moisture than cool air. Your clothes dryer works by heating the air so it is capable of holding more moisture, tumbling the clothes through the warm air to transfer transfer the moisture to the air, and exhausting the warm, moist air from the dryer while bringing in cooler, dryer air.

Dry cabinet plan

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