This is project for people living in tropical climates, who use 'thirsty hippo style' dehumidifiers.
Under hot, humid conditions, stored away stuff (clothes, shoes, musical instruments,..) can get moldy after a while and/or develop that moldy smell.

For bigger rooms, running the air con or electric dehumidifier works wonders, but this does not work really well for stuff stored away in enclosed spaces like cupboards or storage cabinets. This is especially problematic if you are traveling and no one is home to run the air con. The best solution to keep the air in small enclosed spaces dry tends to be using those desiccant based dehumidifiers. Here in Singapore, people refer to them as "thirsty hippos" although a range of cheaper brands are available as well.
These dehumidifiers all contain calcium chloride salt (CaCl2). This salt is extremely hygroscopic: it will suck the moist out of the air and dissolve in the process. When all the solid salts have dissolved, the humidifier won't absorb any more moist and should be disposed of.

The used dehumidifiers all end up in the domestic waste. Here, domestic waste is incinerated, but since CaCl2 won't burn, it will end up being dumped with the ashes.

This is a waste, as the chemicals don't get consumed in the process; all they do is absorbing water. It is actually really easy to recycle the CaCl2: all it takes to restore it to its solid state is simply boiling off the absorbed water again. This can be done by boiling the solution on a simple domestic cook top.

I will demonstrate how to do this, and how to construct a safe new container to put the calcium salt into to use as a humidifier.

Step 1: safety!

Before you consider trying this, consider the following. If you are not comfortable with any of below warnings, please don't attempt this.

Calcium Chloride is mildly hazardous. Although it is used as a food additive, it also acts as an irritant on the skin because of its aggressive water absorbing properties. You also don't want to get it flying into your eyes or ingest it...

Always wear safety gloves and safety goggles.
Keep your working area well ventilated.
Store your chemicals so that they are safe and out of children's reach.

Boiling of the solution will involve heating up the substance to temperatures exceeding those of a typical deep fryer: dangerous!

Some desiccant dehumidifier brands, like "kiwi fresh" contain a fragrance.  Try to avoid heating up those and stick to those brands that contain the pure, odourless stuff. 

I will not take ANY responsibility for accidents and/or injuries that occur while trying or as a result of this instructable!

Find out more about calcium chloride here:
<p>in relation to the material that decomposed quickly...</p><p>PLA or polylactic acid, is biodegradable, 3d printable, and will decompose in under a month in a heat compostable bin.</p><p>so maybe it was PLA.</p><p>but otherwise this is a great idea, have you tried pyrex instead of ceramic?</p>
I use this sort of humidifier in my gun cases. As you said they just go to the dump. I'm going to give this a try using a solar oven to evaporate the water. Living in the desert there is plenty of sunshine. Already have solar water heaters an solar panels, might just as well use it this way.
Instead of heating, is it easier to microwave the calcium chloride solution?

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