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Background

Dorodango is the art of making shiny mud spheres, such as these:

Earth Dorodango Colored Dorodango

To make a dorodango, you collect a core of dirt (optionally mixing in color powder), mold it into a sphere, and then rub it with progressively finer dirt in order to dry it out, until by the end you're rubbing it with dust. When no more dust will cling to the surface, you rub it gently with a cloth to polish it, and it's done. Various sources indicate that it takes a couple days to a week to complete (that is, dry) a traditional dorodango.

Question

If you don't want to wait a week for your dirt to dry, you can speed up the process by using a refrigerator. Wrap the dorodango in a plastic bag, put it in the fridge, and it will increase the rate of condensation, supposedly.

Claim 1: Mythbusters

Claim 2: Dorodango.com

However, Wikipedia says that for water to evaporate faster, you need higher temperatures and lower pressures. In a fridge, you have lower temperatures and higher pressures (due to cold air being denser).

Wikipedia: Factors influencing the rate of evaporation

My guess is that the actual effect of cooling off the dorodango is that the mud contracts due to the lower temperature, which squeezes more water out of the core and toward the surface. I can't find any dorodango sources that mention this, though - they just say that a fridge increases the rate of condensation.

Does putting a dorodango into the fridge change the rate of condensation, or does it just force the dirt to compress more?

  • This is my first question on Skeptics.SE and I wasn't sure what the correct tags were. Please edit freely. – Steve V. Jul 8 '12 at 2:45
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    You also have to consider the effects of the humidity of the air the water is evaporating in to; its possible that a fridge has a fairly low relative humidity. – derobert Jul 10 '12 at 18:26
  • Evaporation and condensation are opposite processes; I think it's clear what (I think) you mean, but you should word this more carefully. You should also word this as a cited claim to be disputed, or move it to Physics.SE // FWIW, I agree with derobert - the air in a fridge is generally drier (and the thermal contraction would not be noticable). – hunter2 Jul 8 '13 at 15:56

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