Analysis of the Black Gunk on Atomizer Coils

[kinabaloo]

A significant downside with a pure piezo approach is that the mist it creates will feel cool as opposed to warm. Perhpas the liquid can be warmed first but that warmth will be gone i suspect before the mist reaches the mouth. The reason for going with heating coils / vapor rather than piezo / mist might well have been because it better simulates smoking / is more pleasant, rather than cost as people have tended to assume.

ps : the tin might be coming from a tin coat on the nichrome wire. http://www.eng-tips.com/viewthread.cfm?qid=5078&page=2

[breakfastchef]

Maybe I am off base, but it seems to me that anything we can do to retard the build up of carbon on the heating element is our best choice to increase the longevity of atomizers. A quick rinse in warm water each and turning the atomizer upside down to drain overnight is the easiest, preventative measure I can think of.

I had my first atomizer fry this week. When I took it apart, the material inside the heating coil was black and brittle. I cannot imagine anything reviving wicking material once it has reached that point. This particular atomizer was only dripped using a variety of smoking juices.

[exogenesis]

Just as a matter of interest,

I forgot that I had evaporated the some of the same e-liquid on piece of metal sheet,
and analysed that as well.

Analysis showed a far 'cleaner' makeup compared to the 'burnt' coil gunk (not too surprising),
particularly NO metals, not even calcium,
but still quite a bit of silicon (from additives or plant extract material ?)

SUMMARY  
       % by atoms % by weight
Carbon    81       75
Oxygen    16       19
Metals     0      0
Silicon    2        5
Nitrogen   1        1

So some (most?) of the metals in the coil deposit must be coming from the coil itself,
especially the tin (from the solder blobs ?).

The sodium. calcium and potassium could be left behind during evaporation/concentration of the liquid,
I estimate a factor of 2000 or so in these tests,
but also maybe some from the atomizer coil as well.

[kinabaloo]

This is an analysis of the dry residue of your e-juice? Slowly evaporated, right. Or the evaporated liquid?

Why don't the sodium, potassium and calcium show up? Because the analysis is of the liquid after evaporation? Before and after would be nice (eek - more work)

What is the 2000 factor?

We need cleaner juices! Say NO to dry residue !!

[exogenesis]

The analysis directly above is for quickly evaporated, but not burnt e-liquid,
i.e. the clean residue after evaporation.
(not the re-condensed vapour we were PMing about).

I guess the metals don't show cos it needs a 2000x concentration
to get a detectable amount of them,
or they are not present in the liquid itself, but come from the coil.
Probably a bit of both.

2000 is my very approx. estimate of 2ml e-liquid converted to 1 cubic mm of coil gunk,
i.e. the residue left after vaping 2ml on a hot coil.

Actually I though that showed the liquid it to be very 'clean',
if you dont burn it,
or contaminate it via a hot wire with solder blobs.

[kinabaloo]

Exogenesis - The carbon and oxygen are showing as with inorganic bonds?

Likely, the dry residue is mostly flavourings.

At present the flavorings used in juices, including those bought from vendors i imagine, are the flavourings made for food where dry residue is not an issue. If juices were made with flavorings with no dry residue, we would have far less of a problem with atomizers getting deposits and the need to clean them / replace them so often.

[exogenesis]

Mostly organic bonds it seems.

Maybe thats true about most of the residue coming from flavours,
perhaps later I'll try this again several times with:

1 pure VG
2 pure PG
3 'flavourless' e-liquid probably TW's
4,5,6... loranne flavours straight from the bottle, or perhaps 1 in 3 with PG,
(I've got some non-oil, 'non-sugar' ones I don't like much)
then ditto, but sugar containing ones
then ditto, but oil containing ones

Trouble is it takes at least 2days to get 10 ml of liquid through the 'autosmoker',
in order not too have it flooding, or running dry too long.

[kinabaloo]

Atomiser death - new theory

We all know that atomizers eventually die and it was long believed, reasonably enough, to be that the fine nichrome wire broke after the repeated stresses of expension and contraction, plus getting thinner as it slowly gets thinner with age.

Sun created a new theory about the final death - through examining many deceased atomizers he noticed that the nichrome wire had been disconnected at the the solder joint; his theory being that as the deposit on the coil grew bigger, it eventually pulled out the wire from the joint.

I think this may play a small part sometimes, but is not the main reason.

A well-soldered joint could not be pulled apart. Unless ... the joint had become weakened.

I believe the solder joint is weakened chemically (perhaps aided by heat) by the juice/vapor. In particular, tin is leached from the solder joint making it much softer and the join looser. Eventually, the electrical connection is lost (and the nichrome wire might even remove its leg from the joint to take up a more comfortable position (i.e. not necessarily with any great force exerted by the deposit growing in size).

The evidence for this - and also the inspiration, though it took a day for the implications to become apparent to me - was discovered by Exogenesis in his analysis of atomizer coil deposits (Analysis of the Black Gunk on Atomizer Coils). The results showed an unusual amount of the element tin within the deposit.

A possible solution is for silver solder to be used for connecting the nichrome wire heater coil.

It remains uncertain what part of the juice causes the leaching of tin and by what reaction or other effect.

Exogenesis - yes, that's a lot of work! Could you use smaller samples for analysis or is 2 days worth the minimum can work with?

[exogenesis]

Good theory, certainly a lot of things can happen at a joint
between two different metals, chemically speaking.

The solder blobs are so large in comparison to the thin nichrome
that if anything I'd hazzard that the wire itself would weaken at the joint.

I like to get a close as possible to real vaping on the auto-vaper,
so getting a reasonable encrustation of gunk is the aim.
Actually the OP was a little light on 'crust depth', so I'll probably
run analysis again when more liquid has been used on this coil.

(assuming the wire etc last that long)

[kinabaloo]

Although i have found reference to tin, among others, sometimes being used to thinly coat nichrome wire, i doubt it is used on our nichrome because it would likely lower the resistance too much. Instead, it is coated by enamel (at least the ones i have are, 901s). The reason for a coating presumably because nichrome otherwise gains a thin oxide layer though since that would be protective, like with annodised aluminium, i'm not sure why this is sometimes done. In the case of the enamel it is just for electrical insulation, for winding overlapping coils and such.

I have not found mention of a tiny amount of tin being part of the nichrome alloy as yet, but it's a possibility. Solder, of course is a much softer alloy so more likely the source.

I am looking into what might attack solder joints - acids might, even VG/PG might have some effect, perhaps on the flux. Any thoughts?

Thinking about it, the maufacturers probably avoided lead based solder and used the Tin-copper-silver variety. So an alternative solder to avoid this problem might need consideration of another alloy.

Exogenesis, perhaps as you alluded, the juice sets up an electrochemical reaction at the join between the wire and the solder. Something like: tiny electrical current because two metals in contact causing an electolysis in which the tin goes into solution.