Most containers are safe but a lot of containers are unsafe so let’s look at what makes a container unsafe for candle making.

 

Two categories are obvious but need mentioning. Those which are prone to crack, and one that could potentially act as a wick.

 

Many porous materials may act as a wick. Clay flower pots for one example. Some believe that the wicking action of the porous clay may draw enough wax to fuel the combustion cycle of a flame. Your 1’’ flame, which originally exists only at the actual wick, could grow to envelope the rim of your container, and maybe the entire container.

 

You may end up with a flame much larger than you expect. For this to happen there are two things which would have to happen. The first would be the previously mentioned wicking action. The second involves the wax that lies on the surface of the container; it would have to get hot enough to combust so producing enough heat to keep the cycle going. While the second event is rare it is possible.

 

As mentioned earlier; the second type of containers seen as unsafe are those prone to cracking. This may well pose a risk when you pour the wax into the container, where it, under heat stress, cracks and wax spills out all over your workplace. Wear solid shoes when pouring wax, at all times.

 

The more hazardous condition exists if the container cracks while burning. Hot wax spills all over the place again. But, this time you also have an active flame going, that is, at the top of a wick. As the wax drains out of the container and runs along your lovely varnish top, it exposes about an inch of fresh, wax-saturated wick. The flame momentarily grows to a height of ten inches, and just barely produces enough heat to catch the nearby furniture, no longer a light source but now a damaging fire hazard in your home.

 

You can do a few things to prevent cracked container candles. Select glassware and ceramics which are intended to withstand heat. Select the smallest wick possible which will produce the lowest amount of heat sufficient for a decent melt pool. Make sure the wicks are as centered as possible to minimize the heat build-up at any localised region of the glass. Use low melting point waxes to help keep things cool. It’s wise to consider all of these things when planning and preparing to make a container candle.

 

Here is another  fact which you need to be aware of. The flame surge which comes from a freshly exposed wick can occur with any kind of candle. A pleasant aromatic votive that has thoroughly liquefied could crack its container, exposing the wick.

 

On a pillar that has been burning for hours, and has a nice melt pool going, a sidewall could suddenly melt loose, again draining the melt pool away from the wick.

 

Even if your glass or ceramic container is considered heat resistant, like canning jars or glassware made specifically for candle making, it can crack. So, the rule of thumb: all candles should be burned on a heat resistant surface, well away from any flammable object such as drapes or overhanging cabinetry, and most importantly, under supervision.