# Silica gel question **URL:** \ **Category:** Factual Questions\ **Created:** [August 19, 2013, 3:36am UTC](https://boards.straightdope.com/t/silica-gel-question/666613 "2013-08-19T03:36:33Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 21, 2013, 5:01pm UTC](https://boards.straightdope.com/t/silica-gel-question/666613/21 "2013-08-21T17:01:08Z")
> [@Thinktank](#): > > I’ve read in plenty of places that the gel can be recharged in the oven since it’s very hydroscopic. What I’m trying to figure out though is if there is a variety of this material that would absorb or deflect/channel or otherwise move away heat from a surface it’s in contact with. With “absorb,” “deflect,” and “channel”, you’re talking about three different material properties. To “channel” refers to [thermal conductivity.](http://en.wikipedia.org/wiki/Conduction_(heat)) You want materials that are good thermal conductors, like copper, silver, aluminum, and the like. Heat sinks are typically made of these materials because they collect heat from a source and move it up to fins that have a lot of surface area to transfer it to the surrounding air. To “deflect” refers to [thermal resistivity.](http://en.wikipedia.org/wiki/Thermal_insulation) You want materials that are _poor_ thermal conductors. In fact, one of the best insulators is no material at all: vacuum. If you’re really serious, you get a vacuum with a few loose layers of thin aluminum foil; the aluminum resists radiative heat transfer, improving even further upon the vacuum. For something less exotic, consider [refractory bricks,](http://en.wikipedia.org/wiki/Refractory_brick) which tolerate high heat and offer good insulative properties. This is in fact an extremely porous collection of silica fibers, so it is in fact similar to the silica gel you mentioned. A variation of this material was used in the space shuttle’s heat shield. To “absorb” refers to a material’s [heat capacity.](http://en.wikipedia.org/wiki/Heat_capacity) This describes how much thermal energy is required to raise the temperature of a material by a certain amount. On a mass basis, hydrogen is pretty tough to beat, although it’s difficult to work with because it has such low density unless you pressurize it. On a volume basis, water is among the best. > [@Thinktank](#): > > I figured if I could just find some that would also wick away HEAT it would be some grand trail to Nirvana to start wrapping electronics in. For instance a silica gel wrap that could be wrapped around a portable HDD which would depending on the amount of wraps give a small degree of shock absorption draw away moisture AND… were it to have some kind of heat channeling ability also would heat the wrap more the device it’s around. Without this property something wrapped around the HDD would only serve to smother the HDD increasing resistance of heat dissipation. That would surely make the drive fail sooner. So you want a desiccant that’s a good thermal conductor with a very low [modulus of elasticity](http://en.wikipedia.org/wiki/Modulus_of_elasticity). I don’t think there’s a single material that fits all three specs. A layer of [silica gel](http://en.wikipedia.org/wiki/Silica_gel) won’t dump heat to the atmosphere better than the bare surface of the HDD, unless you’ve deliberately shaped the silica into a [heat sink,](http://en.wikipedia.org/wiki/Heat_sink) i.e. a geometry that has a lot of surface area (i.e. fins) through which bulk air can flow. Such a geometry is likely to be fragile; mechanical shock will be absorbed by fracture, meaning it won’t be much more useful than a bare HDD. ---
**Author:** ![Poto](https://avatars.discourse-cdn.com/v4/letter/p/7ab992/32.png) [@Poto](https://boards.straightdope.com/u/Poto)\ **Post date:** [August 21, 2013, 10:17pm UTC](https://boards.straightdope.com/t/silica-gel-question/666613/22 "2013-08-21T22:17:07Z")
As a substance, silicagel is not going to be much different from sand. But we use it in the lab for chromatography. In fact is is the basis of much analytical chemistry of organic compounds such as drugs and many industrial chemicals. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [August 21, 2013, 11:24pm UTC](https://boards.straightdope.com/t/silica-gel-question/666613/23 "2013-08-21T23:24:57Z")
I guess the OP is asking if it’s OK to pack a hard drive in silica gel to keep it dry. I’d say no. Silica gel only works because it’s small pellets that are porous. You can’t make a big block out of it without affecting its efficiency as a desiccant. If you use loose pellets of silica gel, it has very poor thermal conductivity (because there is very little contact area between pellets), and it impedes air flow. Besides, I don’t think high humidity is a big risk for modern electronics. As long as you avoid condensation (liquid water). [Previous page](https://boards.straightdope.com/t/silica-gel-question/666613.md?page=1)