Have you ever wondered if a glass candle could break? I have! Is all glass safe for candles? Some glass is not safe for candles, because it is not heat-resistant, can crack, or is porous. Glass that is safe for candles is heat-resistant, does not crack, and is not porous. A good example of a safe, glass container for making candles is pressure canning jars, which are designed to withstand high heat and hold wax well.
Glass container candles are very popular and many people do not realize the risks and safety issues that could arise from burning such an item. I did some research and found some examples of some really great containers for making homemade DIY candles and some examples of not-so-great glass candle containers, as well.
As mentioned earlier, not all glass is safe for candles. Even some "candle-making" glass containers or "certified safe" jars could crack or explode under extenuating circumstances. Glass containers that are going to be used for making candles should have the following characteristics:
ㆍHeat-resistant
ㆍNot crack
ㆍNot porous.
You don't want the glass to break while pouring the wax or when burning the finished candle, so the glass should be heat-resistant and be able to withstand these temperature variances. Otherwise, you will get liquid wax all over your shiny countertop, beautiful wooden table, or whatever other surface was used to make or display your candle. Also, not to mention that shattering glass could cause a not-so-pleasant injury!
Not being porous is another important characteristic of a good candle container. This may seem obvious to some people. Others may ask, "Is glass porous?" Normal glass is not porous. However, glass can become porous if it is etched or cleaned using an acidic and/or alkaline chemical.
When I was researching and learning about this topic and came across this fact, it surprised me. I never thought or knew that glass could be porous or permeable. I guess I always assumed it was a solid block of material that was impenetrable, unless, of course, it cracked.
Many people believe "porous" means that water can get through or it leaks and would protest by saying, "Glass doesn't leak!" However, the actual definition of porous refers to a substance that has small (can be microscopic) holes (or "pores," hence its name) through which air or liquid can pass (also referred to as permeable or penetrable).
Here are some examples of glass and other containers to avoid for your candle-making projects:
ㆍGlass Vase. Can you put a candle in a glass vase? Sure, you could. But would I recommend it? Probably not. Glass vases, intended for water and real flowers, are not made to withstand high heat.
ㆍOld drinking glasses or mugs. These containers could crack, especially if they are old, because they are most likely porous. Depending on the type of glass or mug, they may not be heat-resistant, if they are not microwave-safe or dishwasher-safe.
ㆍClay flower pots or other ceramic, porous containers. Ceramics made from clay or terra cotta are not suitable for candles. They actually absorb the wax and it is possible that it could catch fire. Also, the key word here again is porous.
ㆍAny container that can easily tip over. A container (glass or not) with an uneven or small bottom that could tip over or be easily bumped over is not safe! The wider or more round the base is, the sturdier it will be, which decreases the risk of getting knocked over.
ㆍEtched glasses. These are created with acidic substances and are generally porous and more likely to crack.
Glass cleaned with an alkaline substance. Alkaline cleaners break down the glass and cause it to become porous. Bleach (sodium hypocholorite), ammonia, cream cleaner, toothpaste, metal polish, oven cleaner, and baking powder are all alkaline chemicals. So, if you use any of these chemicals to clean the glass container, the glass could become porous and be more likely to crack.
So, what are the causes of glass candle explosions or cracks? And how do we prevent it from happening?
The situations/circumstances which would cause/create a glass jar explosion, or a glass candle container to break are listed below. I've included tips for how to prevent glass container cracks or explosions.
What causes glass to shatter or break is a big (extreme) difference in temperature changes in a short amount of time, basically temperature (thermal) shock.
ㆍThe first situation would be if the wick is not centered. If the wick is not centered, it will cause an uneven heat distribution on the sides of the container. The glass will become hotter on one side than the other, which may cause it to crack. To prevent a crack, make sure the wick is always centered.
ㆍThe second situation would be if the candle container/jar is not the same diameter along the length of the candle. For example, it has a wider mouth/top and a narrow bottom, or vice versa. When choosing a glass candle jar, it is important to consider the shape of the container. If it is not a completely straight column or even from top to bottom, the container can crack or break, because the smaller diameter section will be exposed to more heat and get hotter more quickly. To prevent a break, chose containers that have an even (equal) diameter across the length of the jar (cylinder that is even from top to bottom).
ㆍGel candles have been known to explode. Gel wax is a clear, transparent wax that has a rubbery texture. The wax is composed of 95% mineral oil and 5% polymer resin. Gel candles are made for aesthetic purposes and have an appealing visual quality. The wax itself actually heats up and therefore heats the entire container, as well. Gel candles are generally made in small, "pretty" containers that are usually thin and clear, such as wine glasses, martini glasses, etc., so you can see the gel. To prevent an explosion, use thicker glass, as mentioned earlier, and the appropriate wax type for the container.
That's all we have to say today. By the way, we are a Glass Candle Holder supplier. If you are interested in our products, please contact us now!
