What does one do with gypsum?
May 13, 2006 1:30 PM   Subscribe

The previous owner of my house left bags of gypsum pellets behind.

I can't figure out what he was using them for in the yard. The soil in the yard is pretty good (not a high amount of clay, which is my understanding of what gypsum is used to break up). Now that I have them, what can I do with it? Mix it into my composter?
posted by archimago to Home & Garden (9 answers total)
Gypsum is almost always good to add to soil. I add it once or twice a year (amongst other things) and it keeps the soil loose enough to allow the grass to put down the deep roots. Use it up on the lawn in the fall (assuming that you have cool season grass like fescue).
posted by intermod at 2:06 PM on May 13, 2006

you could use it to make molds for low-temperature (e.g. zinc, tin)* metal casting.

*(stuff you could melt over the stove in a steel coffee can)
posted by dorian at 4:56 PM on May 13, 2006

Gypsum's a source of calcium, like lime, but it's pH neutral, unlike lime (which is an alkalai). The main benefit of adding lime to a compost pile is to neutralize the acidity produced by bacterial decomposition; that acidity inhibits other organisms (like molds) from continuing the decomposition. So gypsum won't help there. Fortunately it won't do any harm there either, at least not in reasonable quantities. It's also essentially impossible to add too much gypsum to soil so it won't do any harm to spread it in your yard or on your lawn. But if you don't have heavy clay soil it won't really provide any benefit either.

And while plaster is gypsum, pelleted garden gypsum unfortunately isn't plaster. So no mold-making.
posted by TimeFactor at 6:15 PM on May 13, 2006

(h'm! good call TimeFactor, I did not realize that...)
posted by dorian at 7:03 PM on May 13, 2006

There's also the possibility the previous owner bought the gypsum and then either didn't use it or found it didn't do what he wanted. So when he left, he left his junk for you.
posted by smackfu at 7:56 PM on May 13, 2006

Use it as packing material. My husband has in the past had items shipped in it. (I think chemicals, but I may be wrong about that.) I know he brought some home from work or school that we added to the garden.

wife of 445supermag
posted by 445supermag at 9:19 AM on May 14, 2006

Does that mean I can recycle leftover gyproc board into my soil? I don't have a lot of it, and I'd rather not toss it in the trash...
posted by five fresh fish at 11:12 AM on May 14, 2006

So I did some net sleuthing and found this excellent overview of gyproc recycling.

Problem seems to be that when it decomposes anaerobically, it releases toxic gases.

The heart of a compost pile is, IIRC, anaerobic.

If you can ensure it's aerobic decomposition all the way, the stuff is perfectly suited for composting.

Not sure what I'll do with my scraps. It is bloody expensive to drop it off at the landfill; I think because they're then paying to ship it off to a proper recycling facility.

Construction of a 2000sq.ft. home generates a ton of waste gyproc. Yowsa.

What d'yall who live in countries that don't have an abundance of gyproc do for wall board?
posted by five fresh fish at 2:11 PM on May 14, 2006

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