Okay: "Builders" sand is also apparently known as "sharp" sand and, maybe, "paver" sand or just "coarse" sand. I bought a bunch of bags of builders sand that seemed perfect (based on the label, "may be used as a soil amendment"), but when I opened it, I was stunned at how small the grains were. It was rough (just like it's supposed to be) and, unlike play sand or stuff you'd find on a beach, it wouldn't hold together if you threw it in a vat of glue (a good sign; the sand meant for potting mixes isn't supposed to hold any shape).
But man, the grains were small. The sand is supposed to open air spaces, like vermiculite or perlite, so I'm struggling with whether I have the right stuff. When I look at pictures on the web, some of them look small like this stuff, but others show sand that appears to be much bigger (the size of vermiculite, maybe a bit smaller).
Anyway, I've spent well over an hour trying to figure this out and I'm flummoxed. Insight is appreciated. Thanks.
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applestar
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The fine sand is OK as long as you're not mixing it with fine clay. Basically you just want the aggregate mix to contain different size particles.
That said, I've used concrete paver base step 2 for large container soil mix. Step 2 is the one with different size pieces as big as sharp pea gravel down to sharp sand. Right now, for seed starting mix, I'm just using all purpose sand, but in the past, I've used play sand thinking "washed" sand might be better for edibles.
I noticed one time though, that when I used "sand" washed from marble chip gravel and stones, plants grew way better. Along the same idea, there some thing called crushed or decomposed granite -- a quarry by-product -- that is also supposed to be very good. Not readily available in stores around here though, unfortunately. I would need to hunt it down... I think I heard that you could get it from concrete contractors?
As an alternative to perlite, I just ordered some pumice gravel to try.
That said, I've used concrete paver base step 2 for large container soil mix. Step 2 is the one with different size pieces as big as sharp pea gravel down to sharp sand. Right now, for seed starting mix, I'm just using all purpose sand, but in the past, I've used play sand thinking "washed" sand might be better for edibles.
I noticed one time though, that when I used "sand" washed from marble chip gravel and stones, plants grew way better. Along the same idea, there some thing called crushed or decomposed granite -- a quarry by-product -- that is also supposed to be very good. Not readily available in stores around here though, unfortunately. I would need to hunt it down... I think I heard that you could get it from concrete contractors?
As an alternative to perlite, I just ordered some pumice gravel to try.