Silver, (or ssgardener),
That's exactly what I do, but I do use some grit-sized bark pieces and longer thin chips to start seeds, along with 20-30% commercial mix. A 1905 gardening book said that soil needs to be "well ventilated".
What is your finest mesh screen? I'm struggling along with 1/4" galvanized hardware cloth, but I wish I had something a little finer, or even 1/8", to remove the powder and fines..
I have some industrial steel wire shelving that I rest my screens on.
I tied the 1/2" mesh down to some shelving so it stays put.
Then I tied ONE EDGE of my 1/4" screen to that, so I can flip it out of the way when not i n ujse, or to flip off the bigg pieces that did n ot pass through.
I take one pass through 1" chicken wire to catch the BIG chunks, then 1/2" mesh to remove more big chunks.
Then I play around with 1/3" and 1/4" mesh to try to separate "potting" from "seeding" sizes.
If I tilt the screen at a 20-30 degree angle and then pour the bark down the slope and nudge it along with rake or hands, only the smaller bits have time to fin d the holes. It makes a 1/4" screen act a little like a 1/6" screen.
To keep it cleanish, I usually screen into a wheelbarrow and flip the bit bits onto a tarp. Then I save the screened fractions back into the bags I bought the mulch in.
I've been thinking about using a mower, or crushing, or rubbing the coarser stuff to get more fines, but at this price, it's easier to buy another bag and use half or more of the bag as coarse mulch.
Where I live, Lowes has MUCH cleaner mulch than Home Depot. Once I found long bark shreds and chips instead of chunks & powder & some fiber. But that was at a foo-foo nursery, and cost $8 per 2 cubic feet.
Also ... might it be possible to get bark nuggets wet all through, perhaps with steam, and then POP them in a microwave? Like vermiculite is expanded mica and Turface is expanded shale and clay.
These photos don 't show b ark, they show some juniper trimmings that I'm trying to shred with a lawnmower. Since then, I've sharpened the blade!
