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Thread: Silica Gel

  1. #1

    Default Silica Gel

    I've long heard people talking about the baking of silica gel in an oven in order to be reused. And I just watched a video on youtube of silica gel being soaked in water.

    http://www.youtube.com/watch?v=Kxb1ZK86Rcw

    Which brings me to think about what would happen if I microwave silica gel?

    Anyone tried it before? :P

  2. #2

    Default Re: Silica Gel

    The use of gas ovens should be avoided and microwave cookers are likely to damage the structure of the silica gel.
    Silica gel which has been subjected to temperatures in excess of 150oC is likely to be discoloured to a brown or blackened state. If the silica gel has been subjected to overheating the adsorption capacity will have been adversely effected.
    http://www.envirogel.co.uk/improving...activation.htm

  3. #3
    Moderator Octarine's Avatar
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    Default Re: Silica Gel

    Moisture absorption in Silica gel works due to the surface structure of the silica gel. The water molecules are 'stored' in the pores of the surface. If you microwave the gel too heavily the surface will be damaged due to the rapidly expanding water vapor. The cracked surface structure will also release the indicator color (blue: Cobalt Chloride) into the microwave oven. Cobalt Chloride is is a carcinogenic substance. If you want to use Silica Gel then you better check for the orange type.
    EOS

  4. #4

    Default Re: Silica Gel

    Quote Originally Posted by Octarine View Post
    Moisture absorption in Silica gel works due to the surface structure of the silica gel. The water molecules are 'stored' in the pores of the surface. If you microwave the gel too heavily the surface will be damaged due to the rapidly expanding water vapor. The cracked surface structure will also release the indicator color (blue: Cobalt Chloride) into the microwave oven. Cobalt Chloride is is a carcinogenic substance. If you want to use Silica Gel then you better check for the orange type.
    So far I've only seen the blue/pink type though, the orange one seems rather uncommon, at least from the places I've been to.

  5. #5

    Default Re: Silica Gel

    Since silica gel is not so expensive, think it will be better to just use and put in fresh ones when the colour turns to cut the hassle.

  6. #6

    Default Re: Silica Gel

    Silica gel will surely break due to rapid expansion when you drop it into water. Baking requires technique. Start with medium heat for 10mins before proceeding to higher heat, if you subject it to immediate high heat, many will crack.

    Too high a temp and it will the silica will turn into carbon black, rendering it useless. Search the internet for the correct temperature.

    After baking, do not remove it immediately as it will cause rapid condensation on the surface and turn pink fast. After baking, open and put a cover on top of the container and let it cool in the close oven. When turns warm to be hold, take it out and seal up the container till cool for re-bottling

    *Clean oven after use.

  7. #7
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    Default Re: Silica Gel

    Silica gel works fine and can re use by heating at low temp and medium range. I found large scale silica gel re use at electrical power plant (sub stations- they use lot of silica gel for big transformer breathers). They use direct sun light only to heatup and remove water content. Also this also works...


    lastly silica gel is carcinogenic

  8. #8

    Default Re: Silica Gel

    Thanks guys. this was highly educating.

  9. #9

    Default Re: Silica Gel

    Quote Originally Posted by spheredome View Post
    Too high a temp and it will the silica will turn into carbon black, rendering it useless. Search the internet for the correct temperature.
    200-350 deg C.

    http://www.mallbaker.com/techlib/doc...icas/3045.html



    Quote Originally Posted by biker589 View Post
    Silica gel works fine and can re use by heating at low temp and medium range. I found large scale silica gel re use at electrical power plant (sub stations- they use lot of silica gel for big transformer breathers). They use direct sun light only to heatup and remove water content. Also this also works...


    lastly silica gel is carcinogenic
    Silica gel per se is not cancer causing, its the cobalt chloride colouring (blue/pink).

  10. #10

    Default Re: Silica Gel

    Quote Originally Posted by Octarine View Post
    Moisture absorption in Silica gel works due to the surface structure of the silica gel. The water molecules are 'stored' in the pores of the surface. If you microwave the gel too heavily the surface will be damaged due to the rapidly expanding water vapor. The cracked surface structure will also release the indicator color (blue: Cobalt Chloride) into the microwave oven. Cobalt Chloride is is a carcinogenic substance. If you want to use Silica Gel then you better check for the orange type.
    Quote Originally Posted by biker589 View Post

    lastly silica gel is carcinogenic
    Silica Gel itself is not carcinogenic. In fact it is safe enough to be packaged with food. Indicating Silica Gel is beads of regular Silica Gel mixed with beads that have been impregnated with a chemical that changes color when it comes in contact with water. There are two types of Indicating Silica Gel - blue/pink and orange/green. The blue/pink Indicating Silica Gel contains Cobalt Chloride, which is carcinogenic. Orange/green Indicating Silica Gel is the safe alternative to Cobalt Chloride, and can be found at www.silicagelpackets.com.

    Silica Gel can be reactivated for reuse, depending on the packet material. Most Indicating Silica Gel comes packaged in plastic, which shouldn't be exposed to the heat needed to reactivate the Silica Gel - it will melt. Other packaging may be safe for reactivating, but you should check with the supplier first. There are Silica Gel products that are safe to microwave. Even as few as 20 seconds in the microwave can completely dry out the Silica Gel. There will be no damage to the Silica Gel. What you need to be careful about is the packaging, you don't want either the packet or the microwave to get damaged.

  11. #11

    Default Re: Silica Gel

    200++ over is too high probably. Even if the silica does not change, the dye would have IMO.

    I cannot quote the optimal but in oven, I always use 160 degree C.

    Quote Originally Posted by Timolol View Post
    200-350 deg C.

    http://www.mallbaker.com/techlib/doc...icas/3045.html

    Silica gel per se is not cancer causing, its the cobalt chloride colouring (blue/pink).

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