The "Red Bag" Coarse A-3 has a product sheet. If the "Square Foot" A-3 is the same size, this would tell the particle size:
Mostly 6 and 8 Sieve. What's an "8 Sieve"?
I think this is it:
No. 6 - - - - - 0.132 inch opening - - - - - - 3.36 mm opening - - - (bigger than 1/8")
No. 8 - - - - - 0.0937 inch opening - - - - - 2.38 mm opening - - - (smaller than 1/10")
That would be a good size for lots of air and little or no perched water, it seems to me!
(Edited to add - it would make a great amendment to "open up" a mix and make it more airy. But as the only ingredient in a
seedling mix, or a WS mix, is it coarser than necessary? I hope Jonna chimes in with her favorite particle sizes!)
