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It was mentioned in an answer to my previous question that silica gel can be heated in the oven to restore its water absorbent properties. I only have access to an induction cooker, so it possible to use that instead?

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2 Answers 2

If you heat silica gel, you will drive out the water from it. What actually happens depends on how you heat it, and how hot it gets.

If you have a thick layer, you may not be able to effectively dehydrate the crystals in a reasonable time.

If you try to use a gas oven, you're on a loser because burning gas makes water and carbon dioxide - it takes ages trying to do the job with moist heat.

You might be able to do a thin layer in the bottom of a pan on an induction cooker, but remember that you cannot achieve temperature control very easily. The optimum range to regenerate the silica gel is 120 degC to 140 degC, and you really want a gradual temperature rise to do the job effectively - better to hold the stuff at 80 to 90 deg C for half an hour before you go to 120 deg C.

If you try to dehydrate too quickly, the crystals will crack and break up, so you may end up with a fine powder, rather than crystals.

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Are there better ways beside putting in a oven or on a induction cooker. (cause the comments made here make me scare that the silica gel powder can kill or injure people badly) Can I put it under the sun and wait for it to change from pink to blue colour? (I would appreciate if someone can suggest a method that is simple & safe. Thanks) –  Jack May 11 '12 at 2:21
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Wow that's a tricky one! If I had to, not saying that you should (had to CYA) I would use a cast iron pot. Cast iron is the only material that I know, that can heat empty without any ill effects. I would make a rack from crumpled foil (aluminum) since it doesn’t conduct the heat from the induction cooker and will prevent contact with the bottom. Also keep the lid slightly cracked for venting and to prevent the heat from building to high. There are different melting points to various plastics, so I would keep the temperate under 200 degrees since plastic food wrap melts at approx. 220 deg. An oven thermometer would be a wise investment. This may take longer to dry out the Silica Gel but if an induction cooker is the only method available to me, this would be the safer choice.

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If you look at the advice he received earlier you'll see that the target temperature for drying silica gel is 250 °F (around 120 °C, I think). Not sure what the highest temperature is can tolerate is. –  dmckee May 8 '12 at 18:05
    
Yes, but he did not specify whether the silica gel was in a little plastic container, pouch or loose. I didn't want to take a chance. –  Onepotmeals May 8 '12 at 18:12
    
stainless steel can also be heated empty to high temps. It may discolor slightly if you go really high, but not around 220°F. –  rumtscho May 8 '12 at 19:23
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To say "crumpled foil (aluminum) since it doesn’t conduct the heat from the induction cooker" is not the truth - you meant that aluminium doesn't heat up from the induction coil. Aluminium conducts heat very efficiently - or you wouldn't be using it! –  klypos May 8 '12 at 19:29
    
This answer seems entirely speculative, and in the context of a potentially dangerous substance, I don't think we want speculation. –  Aaronut May 8 '12 at 22:39
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