Help with wicking issue

[samslice]

Hey folks,

I'm new to RDAs and have a Vandy vape Pulse 24 BF rda that I'm loving except for one thing. I've been experiencing a lot of spitback and someone at work advised that my wicks were probably over-saturated. I burned off some liquid and, sure enough, the spitback subsided significantly. Now, though, I have another problem. I can get 2, maybe 3 good puffs and then I start to get a not-quite-burnt taste.

I've got a couple pics of the build here that I took right after one of these not-right hits.

A couple things I should note:

• I'm absolutely open to trying other wicking materials if someone has something non-cotton that they swear by. I'm using organic cotton mainly because it's what my local shop had when I bought my new gear.
• The juice I'm running right now is a DIY concoction. The current recipe is 75/25 VG/PG. I've got a test batch of 60/40 steeping that I'll be trying in a couple days to see if that alleviates the issue (also for flavor reasons).

Any tips/advice would be appreciated.

The coils are Demon Killer Tri-Twisted Clapton. I'm not sure of the inner dimension because I don't have anything to measure with.
The cotton is Cotton King, thick enough that the twisted cotton pulled through the fresh coils with a small amount of tension but not so tight that the coils noticeably moved while pulling.

 

[Shawn Hoefer]

First thing I notice is that your coils are riding way too high. You want those air pipes to be pointed at the coils.

The cotton in the coils should be snug, but not tight. Cotton swells, and if it's tight and swells you're choking off the juice to the coils. Conversely, if it's too loose, you'll be running experiencing more spitback as little bubbles of liquid will form between the coils and the cotton that do not fully vaporize, but rather boil and pop.

Hope that helps...

 

[Fredman1]

Wicking tighter just about illiminated that for me. The tighter the better...!
The Morten Oen video put me onto that.

 

[samslice]

The cotton in the coils should be snug, but not tight.

How does one know when the cotton is too tight? I've seen some YouTubers basically say that if the coil moves as you're pulling the cotton through then it's too tight. Is that more or less right, or is there a better gauge?

 

[Zaryk]

I agree, the coils look like they are set too high. When I build the pulse, I set the top of my coil maybe 1-2mm higher than the top of the airflow tube openings (beside the coil), to have the air strike the bottom half of the coils. Your spitback could be because the airflow is missing the coil and not cooling the coils sufficiently. Before trying a different wicking technique I would trim the coil legs down a little bit to drop them down into the airflow.

 

[Letitia]

In the second picture the wick on the back coil has no shoulder. Height is a bit hard to judge from that angle. Did you try raising or lowering the coils a bit?

 

[Alter]

Space the coils a bit (just enough they aren't touching)cause from what I see the middle is burning. I had middle burning issues using contact coils along with using cotton the fibers become plugged from being burnt so no juice flow. I ditched contact coils years ago just cause they like to burn the center. Once that burnt taste appears its just downhill from there. Thin(not trim) the tails some cause being too thick and bulky does inhibit juice flow in both cotton and rayon. Don't over power the build too soon to allow breakin of the build..longer than just a few vapes to breakin a build, for me is at least a tank full if not more in my Subtank mini before the performance begins to climb. Couple primer puffs on a green build helps breaking in. The more mass of a multiwire build the longer cooling off time you need so a couple seconds of after the vape unpowered pull helps cause the already warmed up coil gets red hot much faster than a cold coil so you have to compensate that with pulling faster and being a nasty subohm build you might not be able to pull fast enough not to burn the coil.
Cotton may be too tight is another reason of burnt center so maybe research rayon out. Rayon can IMO easily handle nasty builds much better than any cotton.

 

[samslice]

Space the coils a bit (just enough they aren't touching)cause from what I see the middle is burning.

Part of the "middle is burning" could also easily be caramelized sucrose from the juice I'm running. It's my own DIY juice with Capella Super Sweet, and I know sucrose breaks down at high temps. It's actually the reason I finally made the switch to RDA, so I could dry-burn/re-wick without having to spend $$$ on new atty coils every few days.
That being said, I'll keep the spacing idea in mind in case the earlier suggestions don't quite cut it.
Also, thanks for the tip on rayon. Do you use it and have a particular brand you prefer?

 

[Shawn Hoefer]

How does one know when the cotton is too tight? I've seen some YouTubers basically say that if the coil moves as you're pulling the cotton through then it's too tight. Is that more or less right, or is there a better gauge?

If I can slide it through the coils without moving my build deck around, I think it's good. Many would say it's too loose. The cotton has to fill the coil and make contact everywhere, but that can be done with fluffy cotton that is not packed in there.

Honestly, a lot is left up to personal taste and experience... YMMV

 

[samslice]

First thing I notice is that your coils are riding way too high. You want those air pipes to be pointed at the coils.

I agree, the coils look like they are set too high. When I build the pulse, I set the top of my coil maybe 1-2mm higher than the top of the airflow tube openings (beside the coil), to have the air strike the bottom half of the coils.

I've just reassembled the deck with the coils riding lower. I'll re-wick and let it ride for the day tomorrow and see how that changes things.

 

[samslice]

I've just reassembled the deck with the coils riding lower. I'll re-wick and let it ride for the day tomorrow and see how that changes things.

I can tell already, the lower set of the coils has made a difference in the temperature of the production with all the same settings. Thanks, @Shawn Hoefer & @Zaryk!

 

[Zaryk]

Looks like you placed those coils pretty much in the sweet spot. Hope it does the trick for ya.

 

[sonicbomb]

What wattage are you hitting those coils with?

 

[samslice]

What wattage are you hitting those coils with?

These I'm hitting with anything from 60-70. I keep fluctuating to try and find that sweet spot. 55 is too cool, 75 starts to get too hot for personal preference.

 

[samslice]

I've just reassembled the deck with the coils riding lower. I'll re-wick and let it ride for the day tomorrow and see how that changes things.

So, about halfway through the work day and I had to re-wick. No spitback issues, but I was getting that "lightly toasted" taste again. I think I might be putting too much cotton through the coils. I just did the re-wick, and with about half as much material as last night. I'll see how it does over the next few hours and report back.

 

[papergoblin]

So, about halfway through the work day and I had to re-wick. No spitback issues, but I was getting that "lightly toasted" taste again. I think I might be putting too much cotton through the coils. I just did the re-wick, and with about half as much material as last night. I'll see how it does over the next few hours and report back.

When I wick say a 2.5 ID coil I use about a 1/4" wide piece of cotton (muji pad). I don't fluff it, just pinch and twist one end to get through coil. I pull past the pinched part and cut it off then just lightly fluff ends after cutting to length.

You should feel some resistance when pulling through the coil but not enough to where you have to really work to get it through. Some times the exotic coils may grab the cotton and try to tear it but it really should not try to tear when pulling through.

It really is a thing of trial and error. One of those the more you do it, the more you get it, kinda like riding a bike.

 

[Don29palms]

Wicking tighter just about illiminated that for me. The tighter the better...!
The Morten Oen video put me onto that.

Morten Oen is a con man. Don't listen to a word that guy says.

 

[Letitia]

I don't think he's a con man at all. I think his ideas just need to be fleshed out. Seems to me his focus is simply too narrow.

 

[Zaryk]

I wouldnt neccisarly call him a con man. He doesn't use the same kind of coils we do, so a fair amount of the stuff he does will not translate well to our coil types. He focused all of his attention on what works for his flat hammered coils. He does little to no builds or tests, or whatever, with wire the other 99% of the vaping population uses. That really limits his useful information for the 99%.

 

[stols001]

You can get Graham Cellucotton from Sally's or from Amazon and you need to make sure that you get the box that says 100% Rayon (they also make a 100% cotton version confusingly named... exactly the same thing.

If overwicking is your issue, you may find rayon easier to deal with, it shrinks when wet, and cotton swells.

Also, I'm one of those "More isn't less" people, so I really have to work to NOT overwick rayon even. Tight in the coil is good, and I have found I need drastically less wick than I think I needed.

You may have found your sweet spot with cotton by now, I'm just merely going to note that rayon also burns at a higher temperature, and lasts longer than cotton and can withstand higher wattage.

There's an entire thread on it if you are interested: https://www.e-cigarette-forum.com/threads/rayon-wick-better-flow-flavor-longevity-and-nic-hit-pt-2.706948/page-152

Good luck,

Anna