I am going to try your Catasetinae mix.
After I read this thread I walked 5 blocks to the NYC department of sanitation where they have trucks that mulch wood from pruning trees on sidewalks and parks and I was able to get sawdust at the bottom of the truck bin that is from freshly cut trees that still have moisture content in varying size flakes from fine to medium composed of ash tree, oak, maple, beech and yellow birch.
Bud,
Be careful of such mixes because you don't know what chemicals, diseases or trees are mixed in. Some types of trees give of toxic substances to orchids. I'd hate for you to lose orchids because of toxic or diseased media!
I understand your concern, Steve. But New York City have an array of botanists that monitor if a tree is sick and the whole tree is disposed of and the mulch is incinerated. I have seen it done. The sawdust I have is from healthy trees and they were just pruned. The trees I mentioned do not have toxic sap that make orchids die; in fact they are used for mounting.
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....trivia: the sap of pine trees if ingested by humans can give them stomach ache but they will not be hospitalized.
This pic demonstrates the increase.
I prefer sawdust from ripe heartwood, not from bark. But a bit of bark does not harm.
I avoid used wood with residues of chemicals, paints and varnishes, timber preservative etc.
Sawdust of a chainsaw from beech, hornbeam, birch, ash, poplar, elder, apple and pear tree are promising, to name a few.