Water separation of perlite fines

Some of us use perlite in potting mixes and for starting cuttings. It’s useful to improve drainage without adding weight. However most of the perlite contains too many fines. The fines are dangerous to breath and don’t serve the desired purpose of improving drainage and increasing aeration of our mixes.

So I made up a box with 1/8 inch hardware cloth on the bottom and sides about 4 inches high. This was used to screen the perlite to remove the dust and fines. The key to making this safe and easy was to use water as the separation agent. About 1 inch of pertile was placed in the screen box. Then the perlite was sprayed with water to wet the dust and agitate the fines down thru the screen. In no time the fines are gone without a dusty mess and with minimum breathing issues. I used a hose end nozzle with the adjustable spray pattern. Start with a wide pattern over all the perlite to wet it and knock down the dust. Then work back and forth over the material about twice with a strong tight spray. 100% of the fines are removed.

Fines on the left and course on the right. The fines are wet and clumped together. The course dries out in nothing flat.

I’d say about 10-20% of the initial volume of perlite was removed as fines.


Great idea fruitnut! I use vermiculite as well and could use it for that also.


I use Perlite too,but the particle size is a little bigger,although there is some fine stuff.I found out accidentally,by leaving an open bag out in the rain,it helped to keep the dust to a minimum.
One place that sells it,uses pumice instead,because they find the lighter Perlite floats to the top,when watering.I’m not sure what else is comprised in their mix.With mine,it seems the coarse bark mulch keeps that from happening.
I have used pumice and even pea gravel,in a pinch. Brady

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Back in the old days …

Perlite is a “popcorn” made from silicate sediments. The factories are still here in my county if you’d like to view them … :slight_smile: It is a soil amendment.

Vermiculite is a thin mica silicate, used as a topping in propagation – never as a soil amendment. Fill seeding trays 3/4 of the way with seeding soil, then place your seeds on top, then cover with a layer of vermiculite and mist frequently until the seeds sprout, then slow down the water. Standard procedure in nurseries here.


I have bought perlite at the pot growers supply stores. It’s a much larger grade and has few fines. It still could benefit from this wash technique. I bought it because it was the biggest bag of perlite I could find.

I like to use it for my cacti. It’s expensive here as their are no mines anywhere near. I use DE in place of pumice for my plants, I just wish I could get a bigger size. I would use pumice instead if I could afford to, it is expensive in this part of the country. DE the size of pumice would be the bomb! It holds more water or air than pumice of the same size.

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No pot stores here. At least not that I know of. I’m somewhat skeptical if bigger perlite is really better. I mean getting the fines out is a real improvement. But beyond that I’m not so sure 1/4 to 1/2 inch chunks are really better than 1/8 to 1/4 inch. Maybe someone has real experience with this, I don’t.

I have used both sizes, I didn’t really see any difference. It’s the preferred size it appears for hemp growing. Although my neighbor uses some kind of shell mulch only, all he uses, feeding is chemical and pH of the water with fertilizer is displayed above the water tank, A very cool setup. Full legalization with be on the November ballet in Michigan, expected to pass. Medical only right now. I don’t care either way I don’t use the product anymore.

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I screen my perlite also but I dont use water, I just do it outside when theres a good breeze to blow away the dust. It seems to go faster for me like that. Local greenhouse sells it in 4cf bags for like $25 each so its MUCH cheaper than buying the stuff at walmart or lowes in the small 8qt bags or whatever.

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I have to drive about an hour and a half but I can get 4cf bags of perlite for $8 each at 10 or more bags. I use to use what’s called chunky perlite from joe’s hydro website when they offered free shipping on orders over $200 but now to ship 10 bags of perlite from them is ridiculous. The local perlite here is about half the size as the chunky stuff but still serves it’s purpose.


$8 each? What kind of place is that?

It’s the place that makes perlite, so the price is dirt cheap.