[compost_tea] Mesh'd & Micron'd Out...

From: Kirk Leonard <kirk_at_oregonatural.com>
Date: Wed, 24 Sep 2003 13:52:18 -0700

I think this horse is rode and I'm glad I'm not the only one who was
confused. I'm still prone to some confusion but understand much better than
the first time we discussed this.

"Mesh is an inexact measure" my new filter sales guy says today. Ya. Finally
got that.

"Microns are an absolute number." Exactly.

"Mesh and microns are inversely related." Got that finally, too.

The size of openings in a filter is what you want to know most, hmm? Mesh
values, and mesh tables, vary by manufacturer and material. Together with
the opening size and wire or fiber diameter, you can calculate a mesh using
twpinc.com's calculator if you want to. In any event, you have to know two
of these things to figure out the third.

If you're looking at mesh, you need to know the diameter of the material to
figure if it's actually the opening size you think it is. If your supplier
gave you a mesh table, presumably you can ignore this problem. If you have
a good micrometer or mm ruler and a good eye you could measure it, since we
are talking visible range here (unlike most compost tea contents).

The variance among same mesh values and actual opening sizes is explained by
the diameter of the material, hmm? Tables I've seen tell me the variance in
diameters can be a good bit (even within tables, it seems, definitely
between).

If you know a mesh value and opening size, you can even get what diameter
material it's made of, too. Hey, we can get fancy here... Dennis' is
definitely a chunky filter, I'd guess.

I'm still curious what you paid $67 for, guy. Sounds like it might be
stainless or monofilament? Formed? Framed? Sorry, though, don't think
you're gonna get very many 6.35mm X 1.5875mm critters through a 1.2mm filter
(which is probably fine, anyway... all we need to do is lodge them live,
whatever size, and most in tea are smaller, right?). Maybe they could
slip-slide through sideways occasionally, depends how thick or slithery they
are, I suppose...

I gotta say how ironic it is to be struggling with openings in microns and
meshes in inches. I mean, I can really work easily with a measure of
.000039 inches... huh? "Mesh" seems to be some kind of industrial
"standard" that never became one, other than the rule of thumb that says
lower mesh numbers mean bigger openings, which is definitely useful but
occasionally confusing, though less so now.:) That might be as good a
story as 4 foot 8 inch railroad tracks. Anybody know the mesh story?

Thanks folks. I will never look at baby powder quite the same way again.

-- Kirk













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Received on Wed Sep 24 2003 - 22:58:58 EDT

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