Sciencemadness Discussion Board

Evaporation device (Slow cooker) - any issues with this?

RogueRose - 12-10-2016 at 18:32

I was wondering what the thoughts are about using a slow cooker (crock pot) to evaporate water more quickly. It seems these range from 30 to 300w and range in size from 1c to 5-6 quart (relative to previous power ratings).

I would guess that as long as the BP or decomp temp of the substance isn't too low, then this should be a good choice.

I tried a 2qt 130w pot with CuSO4 and I didn't get the nice crystals that I thought I would get, nor did it stay blue as it reached past the 212 point and continued dehydrating the crystals to reach an olive/tan color and seemed to melt into a flat consistent(ish) blob.

I'm wondering if there are any issues with this or if there are any better options for this?

zed - 14-10-2016 at 13:51

Well, When I need mild heat, I favor using a light bulb. Bulb, inside a closed or upside down, cardboard box, with my material to be dried, atop it.

Incapable of getting overly hot, this machine supplies a nice even heat, over a long period of time, with very low construction cost.

Box may be perforated if required. Low heat chemical reactions, may be conducted inside the box (possibly in a foil covered jar). And, temperature may be adjusted by simply propping up the bottom of the box a little bit. Thereby venting excess heat.

Maroboduus - 14-10-2016 at 14:21

I have used light bulbs as well. I've got a low-temp hot plate made from a lava lamp some idiot friend of mine broke the glass part on.

For evaporation there's also the food dehydrator. These can often be found at garage sales and jumble sales because many people buy them and never use them. They supply low heat and a continuous circulation of air. You could make a cover for one, but I just use the trays which I have cut the middles out of. That way you've got the original vents which are presumably well sized to the heat output.

The crock pots need watching because even though they can be set below boiling, the thermostats on some models have some lag to them, so when the pot runs dry they get hotter than they're set for because without the liquid as a heat sink they heat faster that the thermostat responds. You may be able to avoid this by putting and inch or so of sand in the bottom and putting a container to take the liquid on top of that. If you have any talent with wiring you might be able to solve the problem with a rheostat spliced in to the heating circuit. On non electronic models you may even be able to just put the rheostat on the cord.
My experience is with older models and new ones may be better. I don't know.

Fidelmios - 15-10-2016 at 20:51

Quote: Originally posted by zed  
Well, When I need mild heat, I favor using a light bulb. Bulb, inside a closed or upside down, cardboard box, with my material to be dried, atop it.

Incapable of getting overly hot, this machine supplies a nice even heat, over a long period of time, with very low construction cost.

Box may be perforated if required. Low heat chemical reactions, may be conducted inside the box (possibly in a foil covered jar). And, temperature may be adjusted by simply propping up the bottom of the box a little bit. Thereby venting excess heat.




I was thinking of going with a crock pot myself, but this seems much better. Do you think I could improve the efficiency with a large polystyrene cooler, and a 8W heatlamp drilled into the top? So long as I keep to just driving off water, I think it will work.