A bit back I posted I had an open question about the cotton liner and it's effectiveness at stopping fibers from migrating. My concern was whether the thin cotton liner would stop particulate/fiber migration at all -- even while wet and not compromised. I was/am concerned because:
(1.) This idea only comes from Aspire in
their PR release
(2.) The coil design was specifically explained in terms of wicking and performance; the idea that the cotton was protective only came after the complaints.
Which doesn't mean that the cotton can't be doing double-duty -- a good design might well do that! So it seems we need to know:
(1.) The specifics of the cotton liner being used. It's pore size (space between fibers), etc.
(2.) What weave/makeup would be necessary to stop fiberglass dust/fibers from migrating with the
eliquid and being vaped.
The below is what I came to, as well as how I came to it so you can make up your own mind or help fill in mine.
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TLDR
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Setting aside everything else: I don't see how the liner could work -- at all -- except from keeping the fibers from right against the coil. However there are some open questions listed at the bottom.
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Particle Size
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There's also a neat chart here which gives an example of micron sizes and when things become visible to the naked eye. Aside from just jagged shards causing problems, the realllly nasty stuff is under 5 microns.
https://www.coloradoci.com/bin-pdf/5270/ParticleSize.pdf
For the fine crystaline dust at the sizes we're talking about, you won't actually see it.
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Necessary Pore Size
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I spent some time looking
through what is supposed to be used or is effective for the type of particles we're worried about, as well as other cases where cotton is used as a filter.
[1.] Dust masks
They generally go by effectiveness ratings, e.g. 95%. It generally needs to be specifically rated for fiberglass dust/fibers. Ones that block glycerin and such are R or P series, which obviously doesn't apply as it's letting the
eliquid through. Many manufacturers generally don't list their materials for this, so I resorted to things like alibaba to see what was sold in bulk for those making them.
Commonly it was 100% non-woven spunbond polypropylene/polyester, with N95 (95% effective) ones being 3-ply. Figuring out what spunbond was took me to a dupont data sheet:
http://www2.dupont.com/Separation_Solutions/en_US/assets/downloads/K17041-1Polypropylene.pdf
The pore size for dupont spunbond polypropylene ranges from 56-125 microns. Since we're generally looking at fibers and particulates that are much smaller <5, the standard stuff doesn't look like it would work. There are others that handle smaller sizes better, but much of the increased effectiveness is due to stacking and pleating the layers so they become pads. For an idea of thickness, you can generally squirt 2ml of blood on them without it making it through.
The ones that work the best seem to fully enclose the face and only allow air through special filter valves.
[2.] Oiled cotton filters
There are actually oiled cotton gauze filters, so this looks promising. Two thin layers of metal mesh have thick layers of cotton gauze between them, and a special oil is applied to the cotton. These appear to be generally used for higher-performance auto stuff, and are designed to be free-flowing so the engine can get the air it needs. They work best for bigger things, but not fine dust. They don't seem relevant.
[3.] Paper air filters
Similar to the above, but these are the ones you see near furnaces or engines, and they're generally pleated. The folds help increase surface volume which means they have to be replaced less. It turns out some can do up to 90%, not good enough but better -- but it also turns out these aren't normal cotton but a very specific industrial paper that loses effectiveness when wet. It's also pretty thick, so this doesn't seem relevant.
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Cotton Pore Size
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Aspire has said the liner is 100% organic cotton. No special coatings or anything.
Unfortunately, regular cotton gauze on it's own seems to actually be designed to be porous -- that's one of the reasons why it can absorb liquid so well -- the liquid is filling in all the holes and surface tension between the fibers helps keep it there. Looking up the pore size for cotton (I tried) is like doing it for a screen door.
Based on what I've seen, there isn't that much variation with this between manufacturers as people want their cotton gauze to be gauze.
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Conclusions:
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Aspire says due to the cotton being there it's safe, so we could infer they think fiberglass contacting the coil directly would be a bad thing -- yet it appears almost all of the used coils have compromised cotton.
However, even if that cotton isn't compromised, there is no magic to the cotton liner, they've said it's 100% organic cotton. It can't have the pore size and thickness to stop fine crystaline dust & fibers from migrating with the eliquid right to the coil and up into your lungs.
If it's the case that the fibers hitting the coil exacerbates things, which is not only possible but maybe likely, it may be helping in that way. But it is no barrier to fibers and dust of the size we are really concerned about.
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Open Questions:
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(1.) How well does eliquid transport dust & fibers?
(2.) What role does temperature would play in increasing or decreasing migration.
(3.) What role does temperature play when these fibers/dust hit the coil? Aspire doesn't seem to think that's OK, but does it actually affect the particulates themselves?
(4.) What the H, Aspire?
As always, if I'm missing something or you can help me fill something in it's appreciated.
Ya just can't beat the easy draw on these things! Yet!! 
