Coils "hot legs", we give up and beg for help!

[we2rcool]

We2 are the type that never bother folks when we could be searching and finding "the answer" for ourselves, but we've been searching diligently for months and trying everything we've read and everything we can think of...but we have failed. So we're throwing ourselves on your mercies and begging for knowledge.

WHAT causes a coil to glow from the center out initially, and then become a "hot leg"? (is that what it's properly called? when the positive wire starts glowing hotter than the others and the 'glow' flows from postive to negative, instead of from the center outward?

We've wrapped various coils (from 3,4 to 9,10) out of 30, 32, 34 A1 Kanthal - both single and twisted. With Kanthal Ribbon (.03 and .05, both single & twisted). We've twisted the 'legs'; we've folded the 'legs' on themselves. We've wrapped around plain/cheap silica; German silica; ss mesh; ss cable; ss cable with a mesh sleeve; ss mesh with cheesecloth; nextel; nextel over ss cable. We've tightened, we've loosened, we've poked, we've prodded. Did I mention? We've failed.

These are for typical BCC's (lately, mini David Glassomizers). Our preferred vape is around 2.2 resistance at around 3.8-4.0 volts (or thereabouts) on Ego V2 Megas (or our old Twists).

We wrap the coils and they test, meter, and work beautifully, every one - every time. We vape around 2-3 mls of juice through the tank, take out the coils, rinse them in hot water, soak them in pga for a few minutes, blow them out (from the base) and dry burn them (we check their resistance before dry burning, blow on them to keep them semi-cool while pulsing the heat). Typically after one or two cycles, they're still doing fine. Then somewhere between the 2-4 cleaning, the positive wire starts glowing and they ultimately all turn into scorching hot legs.

We vape (primarily) DIY juices based on 80% VG, with 9% distilled water; 9% saline solution (.9%) and 2% PGA. Nope, it's not the saline. The same thing happens with vendor juices

What CAUSES this? If we could find that answer, we'd likely see immediately what we're doing wrong. We've watched dozens of videos and read hundreds of posts, but no one seems to agree or know. And we can't see anything that we're doing wrong.

Also, is it common for a coil/head to increase in resistance as it's used over time? And if so, why is that? If it's not, is that related to whatever causes the hot legs to gradually emerge?

Fwiw, we've never had a 'purchased coil/head' last much longer than a week either. So we guess it's possible this is just the nature of the beast - because somehow the Kanthal just won't hold up to the heat & use any longer than that (???)

TIA for your knowledge, suggestions and expertise!

 

[Xaiver]

Well, I'm afraid that I can't help with the 'hot leg' bit, because I've never experienced that. I've typically felt that rebuildables are cheap enough to build that I don't even bother cleaning them. Honestly, I'm using -maybe- 10 cents worth of R-Wire and Silica per build...if I only get a week out of it, that suits me. I was using cartos before, and I got approximately a week from one, and they were around a dollar apiece.

More than likely what's happening is a combination of the gunk building up on the wire, and the wire material itself breaking down. Whenever you heat up something and 'vaporize' it, it's leaving behind some residue. If you don't believe me, look in your humidifier. That's obviously a bad example, because tap water is filled with all sorts of junk that's not just water. The liquids in our juice are probably not leaving behind a bunch of scum, but the flavorings are notorious for it. From what I understand, the darker/harsher the liquid, the faster a coil clogs up. You can delay that somewhat by cleaning the coils off, but there's only so much it can take.

Maybe you're not doing anything wrong, maybe the wire can only handle the rapid heating/cooling for so many times before it starts to decay. About the only thing that I see that you haven't tried is another type of wire. I use NiChrome, and I prefer it over Kanthal. I'm in the minority in that, but...y'know, to each their own. A lot of people say that it has a metallic taste, and it sort of does, for the first half/quarter of a tank and then it's normal.

The resistance commonly raises, yes. I've noticed that my coils typically go up 0.1-0.3 ohms over the life of the coil...which is about a week for me.

So, my suggestions are as follows:
Try NiChrome wire. I use 32 AWG and on a 3/4 wrap will get about 1.0-1.3 ohms. The resistance/gauge of NiChrome is a bit different than Kanthal.
Try to go a bit longer between cleanings, that might help prolong the coil a bit. Wait until the taste goes down significantly or it seems dirty.

I don't think that you're going to find a method to make a coil last indefinitely, and a week is a decent amount of time, considering what we're dealing with, and the cost of the raw materials...but I don't think that 2 weeks or a month is out of the question.

Best of luck,
-X