Microcoils and Cotton Wick

[Gordy]

I had my first go at a Micro Coil today using Cotton Wick 
 
 
Cotton Wick
​this isnt a new practice and has been used quite a bit with good results however cotton isnt tolerant to heat like silica and will burn very easily. therefore you must ensure it is wet at all times... burnt cotton tastes foul !!
 
Microcoils
Microcoils work on a slightly different principle to regular coils...so i will attempt to explain 
 
an atomiser coil is simply a wire that resists electrical energy flow. this resistance causes some of the electrical energy to be transformed into heat and light energy. the heat is what vapourises your e-juice. the actual shape you wrap or coil your wire into has no effect on its resistance, therefore an identical piece of wire wound into 10 wraps will heat up the same as if you wound it into 4 wraps. in fact its only actually wrapped into a coil shape to aid in its contact with the e-juice
 
resistance of a wire comes down to three things. the material properties of the wire, its cross sectional area and its length
 
ie the thinner the gauge (cross sectional area) of the wire, the higher the resistance
the longer the wire, the higher the resistance   
 
regular coil with microcoil illustrated below - the red arrows indicate the flow of electricity 
 

 
so on thoses principles you would assume that the microcoil with the much longer length of wire would be of a higher resistance....but in fact they read the same resistance !!!
 
this is because the wraps in the microcoil are touching so what you are doing is creating a wire tube and as such increasing the cross sectional area for the electricity to flow through. in this setup the size of the wraps do have an effect on the resistance, the larger the diameter the greater the cross sectional area.
 
 
 
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i started off with some 0.3mm Kanthal. imo thicker wire is better for microcoils as its easier to get the wraps to touch. I then tightly wrapped it around a 2mm allen key or syringe. make sure to keep the wraps up tight against one another so they touch as much as possible ...i did about 9-10 which came out at 1.4ohms ....12-13 would take you up to about 2ohms but i wouldn't go much higher as you want to avoid making too much of a tunnel for the juice to have to flow through 
 

 
 
i fixed it to the dripper and then removed the allen key
 

 
 
i heated the coil till red and then used long nose pliers to compress the wraps together from each end.
you shouldn't apply too much pressure, it's just enough to hold the wraps together until they cool
do this a few times to make sure that there are no gaps between the coils left 
 
a good coil will light up evenly starting from the middle and working its way outward 
 

 
 
you can now see that all the gaps between the wraps have been eliminated 
 

 

 
 
at this point you want you can check the resistance to see if its what you were expecting.
when happy thread some cotton wool through the coil...it shouldn't be too tight as it will expand quite a bit when its wet
if you use too much cotton wool it could restrict juice flow and you will burn the cotton  
 

 
 
trim off the ends leaving enough cotton to fill the base of the atomiser
 

 

 
 
then prime with juice
 

 
 
...and give it a blast   
 
 
 
 
I cant express enough times the importance of keeping the wick wet with juice
dont wait till the flavour drops off to re-drip as it will probably too late 
 
 
 Findings and Conclusions  

i gotta say i was quite impressed with the microcoil, it certainly produced a lot more vapour than a conventional coil... obviously having the much larger heating area being the reason
 
the cotton wick was interesting, as ss mesh brings out differences in juice compared to silica, cotton seemed different from either of those two.... notable juices being the custard that seemed smoother and the El Toro which had a richer more tobacco edge than i have sampled before.
 
changing of the wick with cotton wick it couldn't be easier... there is no need to replace the microcoil. just carefully pull the old cotton wick out of the microcoil, give it a few short blasts allowing it to glowing red and turn any build up to ash. thread in some fresh cotton and away you go

since i did this in a dripper i have tried it in several other devices like the Kayfun etc... following the same process and rewarded with great results


i hope this is useful, if you have any comments or questions feel free to ask  

[caz]

Thank you Gordy for sharing this with us 

[SamIam]

Nice tutorial Gordy.  I've been playing with those coils too recently and you answered a couple questions I've had. 

[Victoria]

Thanks Gordy, that tutorial kept me busy through most of last night and all of Sunday, the roast did not get cooked!

[corpus]

Great tutorial

It's true..some juices taste better on cotton!

[Gordy]

Thanks Gordy, that tutorial kept me busy through most of last night and all of Sunday, the roast did not get cooked!

oups sowwy

hope you saved me a slice of pizza 

[Victoria]

Good ole Dominos saved the day.....again! 

[TopCookie]

Excellent photos Gordy...   

[Lettie22]

loved it Gordy and thank you so much for taking the time to do this with such great photos and sharing!

Did my first microcoils and cotton last week and been loving them!

[Dom]

Awesome tutorial Gordy. 

[laker]

very good Gordy

[taz96]

 Thank you Gordy. Nice, straightforward explanation that even I as a novice understood. Good clear pics too...

[jdlgail]

thanks gordy gives an old fart something to tinker with, love all the diffrent vaping gagets i can play with, have tryed cotton before and like the flavor a lot better than sicila, you just haft to change it more offten

[laker]

my baby octopuss is cottoned

[mus1cman]

Gordy, That is a  brilliant guide with great info & pics I had tried to do this but could not figure how to get the coil so tight.
 
I have an octopus & want to make a cotton wick  using 32(AWG) 0.20mm kanthal wire, will this wire allow me to do a micro coil as tight as you can make them & how many wraps will make it 1.8 or 2.0 ohms?

[failte]

So Gordy -

I notice you didn't (or at least didn't mention) torching the wire before you formed it.  I'd always assumed that torching the wire, in addition to "annealing it", also formed a non-conductive layer of oxide on it - as is the case with SS mesh or rope.  Do you NOT torch it on purpose for that reason, or is it just not important...

[danwldr]

People only torch the wire to make it less springy

Nothing to do with oxidisation, just some find it easier, some, like me, don't bother.

[failte]

I see.  I keep getting dueling information on the web...  I guess if you look too hard, you can always find contrary information.  In particular, I read somewhere that:

Micro-coil coils touch yes, BUT they do not conduct across that contact "because of oxidation".  Here, I read that micro-coils DO form an electrically continuous tube-like heating element. 

Which I"m not so sure I believe.  Because if that were true, the "coil-tube" would actually have FAR LESS resistance than a coil would.  Wuddinit?

[ericm531]

so it is ok to squeeze the coils together and fire the battery at the same time?

[mus1cman]

 Hi Laker,
I am seriously impressed!!!!! 

I also have the octopus how did you manage such a neat tight micro coil?
 
Any tips e.g.  What gauge kanthal what ohm did you achieve with how many wraps etc…. but most importantly what did you make the coil on & how does it sit in the middle with its long legs to the connections poles?

Any chance of step by step instruction & pics maybe?

[vapingfool]

Micro-coil coils touch yes, BUT they do not conduct across that contact "because of oxidation".  Here, I read that micro-coils DO form an electrically continuous tube-like heating element. 

Which I"m not so sure I believe.  Because if that were true, the "coil-tube" would actually have FAR LESS resistance than a coil would.  Wuddinit?

31 gauge Kanthal A-1 has a resistance of 10.6 ohms/foot - or, very roughly, 1 ohm/inch.

31 g wire has a diameter of 0.009 inches. So if you make a 10 turn coil, the coil length will be about 0.09 inches long - roughly 1/10 inch. So if conduction is from turn-to-turn, then the resistance would be about 0.1 ohm. But this assumes that there is a large contact area between the coils, which is not the case.

If the wires did not deform, the contact between turns would be minute. In the real world they deform, making the turn-to-turn contact surface larger. How much this affects the resultant resistance depends, among other factors, on the ratio of the turn-to-turn contact area compared to the cross sectional area of the wire.

I am not sure how to model this as serial/parallel resistors. I suspect the best approximation would be n-1 (where n is the number of coil turns) relatively high resistances connected in series representing the coil-to-coil contact resistance, bridged somehow by n lower resistances representing the wire resistance.

The end result should be that the resultant resistance should be lower than that of the wire resistance alone, but higher than would be the resistance of coils with large turn-to-turn contact surfaces.

There is a further complication that juice can get in between the coils, no matter how tightly you squeeze them together, which will insulate the turns from each other to some degree.

It would be easy enough for someone to build a closely spaced (but without turns touching) micro coil,  measure the resulting resistance, heat and compress the coil to get coil-to-coil contact - then measure the resistances again - both with and without juice on the coil/wick.

[failte]

But the moment you burn it - actually, the moment it's exposed to air - the outer layer will oxidize.  Everything does - even aluminum.  The difference is that the aluminum ("aluminium" for you Brits) oxide is still silver, doesn't continue to "eat" through the Al like red rust will, and actually makes a protective layer.

BTW - speaking of oxides of iron: there are two kinds (that I know of - IANA chemist) (although pretty much every man I knew growing up was - Halliburton  company town, you know): red rust, and blue-black "rust".  I forget their technical names, "gamma-hematite" and "something else-hematite".  Anyway, the blue-black version is what they put on guns.  They probably do it chemically now, but Back In The Day, gun-bluing was achieved by boiling the parts in salt water, then rubbing it down with steel wool.  Over and over and over.

Interestingly (well... *I* think, anyway), they do the same thing to the water pipes in nuclear power plants.  The blue "rust" is tough and won't flake off and go through the reactor.  The red stuff will, and result in VERY radio-active pipes.  To the point where you can't work on them for longer than a few minutes before exceeding your rad limits (I was an MM on a nuke sub - but it was a new one, so I never came close to exceeding even the civilian rad limit, let alone a military one.   Some of the older boats didn't have it so good, and you weren't allowed to just stand around near primary system pipes.)

(And mind you, those pipes are made of "inconel", iron-copper-nickel, so they don't visibly "rust" anyway - but we're talking on a molecular scale.)

[Nimbley]

so it is ok to squeeze the coils together and fire the battery at the same time?

No, don't fire the battery while squeezing the coil.  You will short the coil with your pliers or tweezers and probably pop the wire.  I have done this by forgetting to lock the button while building a coil.  Had to start all over again.

[danwldr]

LOL

So long as the tweezers are not making any contact with anything metal, it's fine

We earth ourselves out so there is no problem with that, though it is probably best not to, I do 

[vapingfool]

> But the moment you burn it - actually, the moment it's exposed to air - the outer layer will oxidize.  Everything does - even aluminum.  The difference is that the aluminum ("aluminium" for you Brits) oxide is still silver, doesn't continue to "eat" through the Al like red rust will, and actually makes a protective layer.

Not every conductor - and some of the oxides are conductive, such as silver oxide. If Kanthal oxidized, it would be useless in high temperature furnaces. Here is a quote from the Temco site: "Kanthal A-1 is a ferritic iron-chromium-aluminium alloy (FeCrAl alloy) rated for use at temperatures up to 1400°C (2550°F). The alloy has high resistivity and great oxidation resistance."

When aluminum oxidizes (almost instantaneously when exposed to oxygen) it forms colorless Al2O3. If in natural form, it would be called sapphire or ruby.

>BTW - speaking of oxides of iron: there are two kinds (that I know of - IANA chemist) (although pretty much every man I knew growing up was - Halliburton  company town, you know): red rust, and blue-black "rust".  I forget their technical names, "gamma-hematite" and "something else-hematite".  Anyway, the blue-black version is what they put on guns.  They probably do it chemically now, but Back In The Day, gun-bluing was achieved by boiling the parts in salt water, then rubbing it down with steel wool.  Over and over and over.

Well, red iron oxide and black iron oxide.  The old guns were browned/browned (same chemicals, different temperatures) using a solution of  potassium nitrate and sodium hydroxide. I have used both browning and bluing on black powder firearms that I have built.

Sodium chloride would NOT have been used. It is too reactive and would severely pit/corrode the iron/steel.