Chinook,
Fascinating that some posters (or at least one) on the other thread are successfully using the 0.22 micron filters. I don't see how, really, given that the two filters I tried clogged completely the moment the extract liquid entered the filter.
I watched a couple instructional videos on YouTube about using lab syringe filters, and my procedure was correct---draw the liquid into the syringe, then attach the filter to the leur lok, then press the syringe plunger to expel the filtered liquid through the exit spout of the filter. The problem is viscosity. I tried using pure PG and VG with a syringe filter. PG can be pushed through a .22 micron filter, but only by applying great force on the syringe plunger, and even then the liquid comes out the filter exit spout only about one drop every four seconds. VG will not come through at all, no matter how much force is used on the plunger. If pure PG and VG don't work with syringe filters, then obviously extracts made with those bases won't work either.
And yes, I've read from numerous sources that additional filtering of natural tobacco extracts results in negligible flavor loss, but that wasn't my experience yesterday with the syringe stuffed with cotton rounds. Using my instant coffee extract, the flavor loss from that method was severe.
I feel no need to further filter my tobacco extracts. They're fine as they are (and yummy, by the way). The two-stage filtering I do (first through the woven nylon mesh filter of a large Melior French Press pot, then through a paper coffee filter in a Melitta cone) is adequate for my tobaccos. All I'm trying to do is clean up my instant coffee extracts so that they don't gunk up coils so quickly. The coffee extracts taste great; I just want juices made with them to vaporize more cleanly.
My abiding rule in vaping is, "If it isn't fun, don't do it." Making coffee extracts is beginning to approach the "not fun" zone, so maybe I'll stop messing with them.