Hi does anyone know if Desiccant Silica Gel that you get in things you buy to absorb moisture is the same silica gel that is sold as a moisture retaining aid in potting compost? Thanks Tricia
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19 years ago
Desiccant Silica Gel
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19 years ago
It isn't.
Silica 'gel' isn't a gel, it's a solid crystal.
Mary
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19 years ago
Until it gets saturated with water, at which point I expect it's quite gel-like.
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19 years ago
I've never heard of silica gel being added to compost, and I can't think what good it would do.
The stuff in compost is either vermiculite (white, porous, dusty) or a polymer (softer, maybe clear, no dust). Neither works as an effective dessicant for the air.
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19 years ago
Not the indicator gel type at any rate (the sort that goes pink when wet)
- stays crystalline
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19 years ago
Nope, not even when it's wet as a really wet thing.
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19 years ago
This is just silica gel with added indicator.
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19 years ago
No, it's still solid when it can't absorb any more water. That's why sometimes it has a colour indicator added to let you know when it's saturated.
It's easy to refresh in an oven. But it's never a gel and I wondered why it was called that when I first used it fifty years ago in the lab.
Wondeful stuff - but never, ever lick it!
Mary
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19 years ago
Silica gel is lickable, although I'd hardly recommend it.
However _never_ lick the "crystal" cat litter (an acrylic polymer absorber). Good stuff though, if you have an older cat that's gone particularly pungent.
DAMHIKT ....
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19 years ago
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are the crystals that are added to plant compost, so what is Desiccant Silica Gel made from?
Thanks Tricia
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19 years ago
so it's ok to lick the non crystal cat litter ;o)
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19 years ago
Bad news: it absorbs spit so dramatically that it can stick to your tongue - as I found out to my cost :-(
Good news: it's not poisonous :-)
Assuming that you have experience I promise not to do it.
Why on earth would you want to?
? That's one I don't think I've seen before and can't work it out. Well, can't be bothered ...
Mary
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19 years ago
A good question indeed.
I feel an urge to go find some and try it right now :-)
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19 years ago
It is silicon dioxide. It's called a 'gel' because it has a very porous structure (which is why it's a good dessicant).
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19 years ago
Don't ask me how I know that.
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19 years ago
poh.
S'obvious, really ... thanks :-)
Thinks - I wonder how he knows it ...
Mary
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19 years ago
I didn't know I had a child called Morley ...
Mary
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19 years ago
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a nice (if badly spelled) site.
Mary
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19 years ago
To discover whether it was a super-absorbent polymer or not. It is.
Or rather "If ith" 8-)
Don't ask me how I know that.
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19 years ago
They're the polymer sort (so not really "crystals")
Silica gel is "fluffy glass". It has an adsorbent surface, so will adsorb (with a "d") moisture from the air and hold it on the surface of the beads. Because this just happens at the surface, it's a limited volume.
Vermiculite is similar, except that it is porous throughout and so can hold a useful amount of water for a plant's needs. It also has a less active surface than silical, so it won't adsorb water vapour from the air. Fuller's earth (if we're talking cat litter) works similarly.
The polymers absorb (with a "b") moisture, the difference being that it's a volume effect, not a surface effect. They aren't strong enough attractors to work as a dessicant, but they will absorb a _lot_ of moisture, hence their use for plants.
If you just need a small quantity of the polymer, cut some disposable super-dry nappies open.