I disagree. While you don't need one to make hash, a freeze dryer removes 100% of the variables when drying. Pedro and Frenchie both say it's the biggest factor for creating quality hash, and after seeing the difference I totally agree.
I run a nice little ice maker, as well. Using RO water for everything from the wash, to the ice, to the rinse.
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Again referring back to Pedro and Frenchie's methods -- I run without any work bag at all. The cold water vortex is what breaks the trichomes off, so you actually increase yields greatly w/o a work bag holding everything into a big mass.
For the sieving bags 100% mesh should be a requirement, though. Cheap bags will make inferior product -- the mesh can stretch, the stitching comes undone, and they can release broken fibers into your clean hash.