Candle making trouble shooting

[Jimmy]

Making a few candles using silicone moulds, I often get the cavities shown below as the wax solidifies.
The wax was at 70-71°C when poured, room and mould temperature was 18°C.
Any tips please on how to correct? I have been pouring some more wax in once they have cooled but would prefer to get it right 1st pour.

 

[Mint Bee]

only way I've found to avoid this with larger candles is to reduce the temperature gradient by keeping the moulds in a cool oven (say 40C) and then putting the filled mould back in the oven until set. Wax is less inclined to shrink back, but its a bit of a faff and slows the process down. I use polycarbonate rather than silicone moulds, so don't know if this would make a difference?

 

[IGPebble]

Some cavitation is inevitable depending on the candle shape, if it's long and thin it's especially likely to cavitate.

Cavitation is caused by two things, the temperature (and therefore density) of the wax and the air temperature. The cooler the wax is the less cavitation you will have (aim for 68*c max and stir thoroughly before pouring to make sure the wax temperature is even).

Next you want to let them cool slowly, for smaller fatter candles this doesn't matter so much, but for larger or thinner candles it's very beneficial. Aim to have the room temperature at least 21-22*c (warmer the better), alternately use a honey warming cabinet set to ~50*c and warm the moulds before pouring then leave them inside the turned off honey warmer and let them cool in the residual heat.

As beeswax gets more dense as it cools, having a reservoir above the mould can allow it to pull that needed wax in (depending on the mould, also requires very slow cooling), or you can do a second pour whilst the candles still hot to fill any gaps.

 

[Jimmy]

Thanks both, will try using my warming cabinet to pre-warm the moulds and then slowly cool the poured candles.

 

[jenkinsbrynmair]

pour slowly, then every few minutes, before the wax solidifies, top up where required.
With dinner candles and the like it's worth gently drumming your fingers up and down the moulds for a while so the bubbles rise quicker
I do all my candles in the outhouse, a lot during cold weather so no heating obviously. Never bothered with faffing around with a warming cabinet