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Flashpoint is one of the most debated and misunderstood concepts with regard to fragrance and essential oils.
Merriam-Webster defines it simply as: "The lowest temperature at which vapors above a volatile combustible substance ignite in the air when exposed to flame." In simple English, how warm does the fragrance or essential oil need to be before it will catch fire if a spark or flame is near?
For purposes of this article, we'll refer to both fragrances oils and essential oils as fragrances. As chandlers and soapers, flashpoint is important in two instances:
First Case, as you make candles or soap the aroma bottles will likely be near your heat source to melt the oils and waxes. If you have a low flashpoint fragrance you may want to take extra care when the bottle or other measuring container are open since the fumes may be able to ignite if a spark/flame/cigarette, etc for example are near AND the bottle of fragrance is at the temperature of the flash point. For example, if you have a bottle of Lime Essential Oil (Citrus Aurantifolia) the flash point is 114° F (45.5° C). That bottle will need to reach 114° F (45.5° C) AND be exposed to a spark or flame to possibly ignite.
Once the oil is blended well into your soap or candle wax the flashpoint rises to be the combination of ALL ingredients in the blend. Let's say that a different way. Once you blend that Lime essential oil into another ingredient the flashpoint of the whole blend changes. If you were to, say, mix the lime essential oil with olive oil in equal parts, the flashpoint becomes much higher since the entire blend will need to be warmed to a much higher overall temperature before the fumes may ignite when exposed to a flame or spark. Once you fully and completely blend those fragrances into your melted candle wax into a stable homogenous blend the new flash point is the combination of the waxes and fragrances.
Here's where many people become misled. Someone somewhere once upon a time instructed people to lower the wax temperature to the flash point of the fragrance before adding the fragrance oil to the wax to some how magically maintain the finer fragrance notes. If the wax temperature is too low, you run the risk of the low flash point fragrance not being homogenous in the candle. Candle waxes create various crystals as they cool. The warmer the candle wax is when blending in fragrance (and color) the more uniform the candle wax will likely cool. If was is too cool when adding fragrance (and color, etc.) the crystals will be different sizes and less able to hold additives as the manufacturer of the wax intended. imagine adding pebbles to concrete after the concrete has begun to harden. The whole block of concrete will be fragile since mixing things in as it has partially set disturbs the bonds of the concrete recipe.
Inadequately formed crystal structure in your candle can lead to seeping and pooling of the fragrance. Sometimes fragrance can seep out the pores on top of the candle and appear as dew or wetness on the surface of an improperly made candle. Pools of low flash point fragrance next to a flame in a lit candle can "flash over", the technical term when the surface of the candle catches fire. When a candle is improperly made causing fragrances to seep/sink to the bottom of the candle, the candle can catch fire when the flame reaches those pools. Flash Over is an immediate candle safety fail. All candles made in that batch should be recalled immediately according to the ASTM standards.
Second Case: Shipping the Fragrances and Essential Oils.
The US Department of Transportation has clear guidelines for how hazardous materials (HAZMAT) must be packaged and shipped. many fragrances and essential oils are classed as HAZMAT based on the flashpoint.
Since many of us rely on the US Post Office for common shipment needs, here’s the link to the regulations spelled out in their words. The regulations are the same for UPS and FedEx. A separate blog post is being written for this specific topic.
CLASS 3 FLAMMABLE LIQUID
Includes materials whose Flash Point (FP) is between 100F and 141F.
must be shipped ground.
may not be shipped international.
CLASS 9 MISCELLANEOUS DANGEROUS GOODS
COMBUSTIBLE LIQUIDS Materials have FP is between 141F and 200F.
shipping regulations are a bit complex, and will be covered in another blog post.
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