What I have found with my builds is that the greater the tension that I impart, the tighter the coil, and the greater the coil memory. With kanthal, and using a coiling jig, I can get the coil tight enough to resist uncoiling and maintaining its shape rather well without annealing, or torching. I insert the coil and then begin prepping the circuit. Here's a coil made without torching or annealing:
Now, the heat is critical to preparing the coil for use. Kanthal has some superb properties which surprisingly include both thermal conductivity and electrical resistance. My friend, State O'Flux, has an excellent blog (
http://www.e-cigarette-forum.com/forum/blogs/state-o-flux/5429-micro-coils-why-they-work.html) about why kanthal needs to be heated/pulsed in preparation for
vaping:
"It is not voodoo... it's the way the wire is designed - and this "feature" of Kanthal has been well known since before you were born, and just one of the qualities that make it so common and useful.
When heated, Kanthal wire (iron-chromium-aluminium) builds up an aluminum oxide insulative coating on it's outside surface that protects the individual coils from shorting, one to another. This is called alumina (Al2O3).
This is most clearly noticed when you test fire a well compressed coil... the coil initially shorts and heats unevenly. The more you fire it however, the more evenly it heats - from the center out. This is the alumina layer building up and insulating the coils surface.
That is it. No magic... unless a self-generating, protective oxide layer is considered magic. Maybe it is magic - Kanthal wire is both thermally conductive and electrically resistive. Pretty convienent for us, and several billion other handy applications for heating coils.
Consider as well... for a given length and thickness of wire, the resistance does not change whether it's a 7 wrap conventional coil or a 7 wrap compressed coil.
Again, resistance for a given length does not change any appreciable amount - what does change is the amount of heat the "compressed coil" is capable of generating. Reduced to a short, concentrated segment or element, the heat generated for a given resistance/area can be greater than the sum of parts.
Why you ask? A simplest answer.
As stated, you have concentrated the heat generated by the individual coils into that smaller, more cohesive heat generating "element".
So, if you're still on the fence, consider this analogy. Ten matches, lit and separated by 1 inch per match, generate the heat of... 1 match or individual heat source per inch.
Now, ten lit matches, all within one square inch... 10 times the heat concentration / compressed down to one square inch.
Last, although "micro" is used to define a small diameter (1.5mm or 1/16" - or less), compressed coil heating element, you can compress a larger diameter vaporizer coil and have the same result of greater heat concentration for a given dimension of resistance/area occupied."
What seems to often get confused is the need for heat to help the coil with the need for heat to prepare the insulated cover of alumina oxide when firing the coil. They are two different issues. Heating the wire before or after wrapping can and does remove the springiness, but so does tension, which also imparts strong coil memory and superb tightness, compression and adhesion. This is what Mac has been talking about for a while. I can't get that kind of tension in the coil myself by hand, so I've resorted to the use of jigs, and I'm continuing to refine them. All I know is that they work great in creating the coil, pulsing my battery after coil installation works great in preparing the coil for
vaping. Together, the "magic" of the kanthal micro coil/COIL is focused concentrated heat right where we need it for our best vaping. My two cents. YMMV. Good luck!
