Letter: Silica Gel Packets


Hoping you could answer a quick question. I put two jars full of silica gel packets in a glass jar and set them in a oven at 200 degrees over night to dry them out. I noticed that a couple of the bags broke open and the silica gels were brown. Does that make them non effective. I thought they were white to start with.

Thank you and may God’s blessings be upon you and your family.

P.S.- I liked your comment on one of your interviews where you stated your prayer is for God to put you in the right place at the right time with the right people. Very nicely said. – G.

HJL Replies: I had to ask one of our long time readers, and he had this answer for you:

Cobalt chloride (incorrectly called Silica) will usually turn blue when reactivated. It is pinkish/purple or just light blue when “wet” and is a heavy metal salt that is toxic. Brown “silica” (which isn’t silica at all) is usually “chippy” and turns dusty with age. I guess it depends on what color they started life out as.

Actual silica gel is a porous granular form of a synthetically manufactured product made from sodium silicate, which is indeed a very high capacity adsorbent. Capillary condensation is the process involved in adsorbing moisture. It is non-toxic and is food safe. Most gel is labeled toxic and is in the cobalt chloride form. Real silica gel turns a very dark green when exhausted, but there may be some iron salts in a high capacity version which may turn from a deep orange to a pale yellow when saturated. The orange MIGHT be construed as brown. It can adsorb up to 40 percent of its own weight in water.

The container they are in is usually tyvek, which has a melting point of 250 degrees F. It is indeed important to check the oven’s temperature with a thermometer. I recommend heating to 235 degrees for at least 3 hours and certainly no more than 250 degrees. Caution is in order because the fluctuation of oven temperature is pretty wide in most ovens. Other materials such as plastic and metals are also used for a silica container.

Long story short, it’s probably old stuff and the toxic version of “silica”. – F.B.