Desiccant

[Melissa Westlake]

We have exhibit cases built in the late ’80s that have slide-in desiccant trays under the artifacts, due to the fact the gallery can get humid in the summer.  These haven’t been maintained in several years and the desiccant is definitely no longer actively working.  I am unclear whether the current desiccant can be refreshed (and if so how?) or if I need to buy new.  All the products I’ve seen online are small packets, and I would need to buy a fair amount – about 14 baking-sheet size trays full!  If buying new is the answer, can anyone suggest a place to buy it more cheaply in bulk?

[Karen Louvar]

Silica Gel can be reconditioned by placing in the oven at 250 degrees for an hour, and it will change color.  

Desiccant can be bought in bulk  through http://www.universityproducts.com (Holyoke, MA).

[Ron Kley]

Silica gel is the most commonly encountered dessicant and, as Karen Louvar has suggested, it can be revitalized by simply baking it and driving off the water that has been absorbed.  That process would probably be accelerated if the oven door were to be left open for water vapor to escape.

[Barbara Appelbaum]

You may not want to dry out the silica gel completely.  If you are displaying metals, the lower the RH the better, but if it’s wood or paper or textiles, the RH shouldn’t be under about 35%.  Before you put anything in the cases, you should put in the silica gel, let it acclimate, and measure the RH.  Even with very dry silica gel, most cases aren’t very air-tight – and even well-sealed Plexi or glass vitrines leak on air exchange per day, so that’s why you need an independent reading of what the RH really is.

[Devon Pyle-Vowles]

Word of warning about baking silica gel — be very careful you can also do damage to yourself – you need to wear a mask and possibly wear gloves. Silica can dry you out  a lot. Also, you can buy dry and preconditioned silica from Art Preservation Services http://www.apsnyc.com/

Their website also has instructions on working with silica. Good Luck.

[Kathleen McCormick]

Ditto on that last warning; wear gloves and a dust mask. Also be careful with silica gel containing a cobalt chloride color-changing indicator.  You should have the MSDS for the gel you’re using but I would also recommend visiting the Conservation online website at:

http://cool.conservation-us.org/

and googling “silica gel” for more than you’ll ever want to know about the stuff: its uses, conditioning, health and safety and suppliers. Prepare to be overwhelmed!

[Rachael Arenstein]

Unfortunately the APS offices were badly damaged during Sandy and they are not fulfilling orders at this time.  There may be stock of their gel at other preservator vendors.

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