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Let's say you spill 10ml of water on the kitchen counter. It forms a small puddle that would evaporate after a while (assuming room temperature and sane humidity). Would spreading a large, dry towel over the puddle cause the water to evaporate quicker? What I mean is a towel that's much larger than the diameter of the puddle. Say 4x as large.

On the one hand, the water by itself comes into direct contact with the air which causes it to evaporate. On the other hand, assuming the towel absorbs the water almost entirely, it increases the wet surface area significantly, but also "locks" away some of the water in the fabric where it has less contact with air.

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    $\begingroup$ Yes, I know I can just try it out and see... but where's the fun is that? $\endgroup$ – Assaf Lavie Jul 30 '13 at 20:17
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I think it would evaporate quicker for anything we normally call a "towel". The evaporation of the plain puddle is limited by the surface area of the water. A towel provides many capillary pathways for the water to diffuse thru the fabric, eventually presenting a much larger surface are for evaporation. Other fabrics could be hydrophobic and decrease overall water/air surface area, but the point of a towel is to do the opposite.

Assuming the towel is clean and not causing additional impurities to dissolve into the water, the vapor pressure of the water should still be the same. The towel is then just a mechanical support for lots of capillary channels. I don't think the vapor pressure is lower just because the water is held by capillary action between structures like cloth fibers.

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I think it will depend a lot of the amount of water, thickness of the towel, microstructure of the towel, and size of the towel. I believe that we cannot have a concrete answer to your question.

The water will only evaporate in contact with air. If the towel was the exact size of the puddle, it would take more time to evaporate (the contact area with air would be the same, and you had to add the diffusion time through the towel).

If you had a larger towel, we would have to know how fast would the water diffuse in the towel (thus depending on the thickness and microstructure). It could take less time (because you would be increasing the contact area of the water with the air) or it could take longer (because the diffusion through the towel could not compensate).

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