Wicks and concave tops

[kate]

Has anyone noticed having to wick up on molds with concave tops, as opposed to flat tops?

I just got a bunch of new aluminum molds and they have the concave top. I used to only use the metal ones that have a flat top (and by top I do mean bottom of the actual mold). I usually use 24 ply in my 3x4 round candles, but the ones with the concave tops are tunneling.

Anyone else had this happen?

[SatinDucky]

Mine are concave and I use 24 ply for most all scents....

[Dee]

Haven't found any difference betwee the two. More likely I find a difference when I use different FOs but same waxes.

[kate]

I used the same wax I've been using, the 4045H, and the scents I've tried aren't new either. I'm quite perplexed now! Thanks for the input!

[topofmurrayhill]

I'm glad you brought this up. Some people say it doesn't make a difference but of course it does. A pillar burn is a delicate balance and if you do careful tests for wicking you'll see the shape of the mold can have a big impact.

The rim or shell that forms around the wick acts like a brake and slows down the burn. Concave molds start with a rim built in so they burn a little more consistently from top to bottom. Flat topped molds have a distinct sprint on the first few burns, then the rim start to form and they settle down.

If your burn pattern is the same for both, it can affect what you see on many subsequent burns or even all the way to the bottom. What's happening with the concave mold is that you're establishing a different balance right at the outset. Molded rim = slower burn and slower burn = more shell so it never has a chance to catch up and suddenly you're underwicked.

It underscores how we can only wick ideally for a particular burn pattern. People can burn the candle differently and performance can vary dramatically. It also illustrates what the memory burn is all about and why it can be important.

Unless your burn cycles are just too short, you might need to wick up a little bit. I wick my 3 inch pillars to perform best with approximately 4 hour burns and I use both types of molds with the same wick. Ideally, I wish I could provide instructions to do a shorter memory burn on the flat tops, but that's too complicated and people will do as they please anyway.

[kate]

Thank you for chiming in, I really thought I was nuts. I test in burn cycles of 3 1/2 to 4 hours for my 3" pillars, mainly because I preach to everyone who buys a candle about burning it the first time an hour for every inch of diameter ... etc., etc.

I'm usually a little conservative on wicking because I fear the powerburners who let candles burn for 6, 7 or even 8 hours and wonder why the wax is in a big pool on the floor. I like a little shell left at 4 hours, enough that the wax won't break through if someone does let it go for a long time. At the same time, I worry about someone only burning 2 hours and it tunneling the whole way down. Ahhh, the frustrations of wicking.

I had all my metal molds down pat with the wicks, and I was hoping these new molds would act the same, but I guess it's just time to test, test, test and then test some more!

[topofmurrayhill]

That sounds like a good burn cycle for testing. In that case I think wicking for the concave molds is really the best solution. Those will burn correctly and consistenly and the flats might burn a little hotter than you like at the beginning but I can't think of a way around that and still use the same wick. They should settle down and perform similarly to the concaves after a few burns.

[kate]

I don't care about using the same wick in the flat and concave - I have several odd-shaped molds that I use different wicks for - I was just hoping that I wouldn't have to start all over with testing. Since the 24 ply works well in the flat, I was assuming it would work just as nicely in the concave - and once again I learn that I can't assume anything.

Thanks for your input Top, I really appreciate it!