Why is Polarity so important?

Gel is a non-polar substance, therefore it will only mix completely with other non-polar substances. It can sometimes appear to mix with some polar substances, but looks can be deceiving! Even though it looks as though it's mixing well now, the likelihood of separation down the road is greatly increased. Due to the wide variety of ingredients used in fragrance oils, the end result is a wide range of polarity levels in the finished products. Some oils are more polar than others, some more non-polar than others. In order for a scent to mix properly with gel it needs to be as non-polar as possible. Polar fragrances can cloud the gel, which is a sign of separation. They can also form pockets, or " pool". Pooling can occur anywhere throughout the candle, not just on the top where it can be easily detected. It can sometimes take months for separation and pooling to occur. If you burn a candle that has "pockets" of fragrance oil that have separated, once the flame reaches that oil pocket it will likely flare up, causing possible injury or fire damage! Polar fragrances also lower the overall flash point of the gel to a greater degree than a non-polar fragrance with the same flash point.

Penreco's Stance on Polarity Testing -------------------------------------------------------------------------------- The following is information posted by Edward from Penreco in answer to the recent questions about polarity testing. There has been quite a lot of talk recently about the polarity test. Who came up with it? Is it accurate? Why do it? What does it really mean? I will try to keep this short and simple. The test was developed by our labs with input from fragrance houses to design a simple test for the polarity of fragrances with mineral oil, the predominate material in candle gel. Polarity and flash points of the fragrance oils have been identified as the main cause for candle gel fires. We have been able to produce candles that flare in our labs and have conducted reviews of the remains of candles given to us that flared. Polarity and over scenting were the main culprits. The tests of one part fragrance oil/3 parts mineral oil and 3 parts fragrance oil/one part mineral oil is conservative, simple and accurate test for polarity. This is what we wanted, to design something anybody could do. If the fragrance you are testing separates or creates haziness in either of the two blend ratios, then there is a chance that there is some polar structure to it. For safety reasons we wanted a conservative, simple test and that is why it is done with mineral oil, not gel. Fragrances themselves are complex chemicals and there are numerous vehicles that are used as carrier oils. A simple test for a complex chemical needed to be designed and that is what the polarity test is. Obviously Penreco wants to see this market continue to grow, we have committed capital and resources to our gel business for 10 years now. We have been producing and marketing gels for over 9 years. We feel the candle gel market is no fad, and we plan on supplying candle gels for many more years to come. Because of this we are committed to the safety of the consumer. A fail proof polarity test is part of the overall package of safety factors that we feel needs to be passed on to the industry. There are a number of companies that have been started to serve and supply this industry, that is great and we applaud and welcome their efforts. But the safety information that we pass on has been developed over several years and with help from many. If you want to see more on the safety and handling of Penreco candle gels you can visit our web site at www.penreco.com.

What is a flash point?
A flash point is the temperature at which a substance will flash, or catch fire when a flame is passed over it. The flash point of a fragrance is important because adding fragrance to the gel lowers the gel's flash point. For that matter, adding any substance with a lower flash point than the gel itself, will lower the finished product's flash point. You want the end result flash point to stay as high as possible, no less than 100F degrees above the temperature of the melt pool. The flash point of Penreco Versagel™ is 440F. The melt pool temperature refers to how hot the melted gel around the burning candle's wick gets.

The melt pool temperatures for the various types of Versagel™ are as follows:
CLP (Low Density) = 258 F
CMP (Medium Density) = 275 F
CHP (High Density) = 281 F
(The average paraffin wax candle melt pool is around 170F)

You want the overall flash point of your gel and fragrance mixture to be at least 100F higher than the gel's melt pool temperature (ie: 375F) to ensure that the melt pool will not be hot enough to cause the gel to flash (catch fire or flare up). Let's say you're using 5% non-polar fragrance oil with a 170F flash point, and 95% gel with a 440F flash point. 5% x 170 = 8.5 and 95% x 440 = 418. When you add the two totals of 418 + 8.5 and you get a final flash point of 426.5. This means by adding that fragrance oil, you've lowered the flash point of the gel 13.5 degrees, or a little over 3%.
This is still a safe level, but also the lowest recommended. If you were to over scent the gel and use more than is recommended, it would lower the flash point even more. Even if you were to use a fragrance with the same 170 flash point, but that was polar instead, because of the chemical nature of polar oils, it would lower the flash point of the gel even more than the non-polar one.

How much to use:
Penreco recommends using no more than 3% (1/2 oz per pound) in Low Density gel, and up to 5% (3/4 oz per pound) in Medium or High Density gel. Measure your fragrance by weight, not liquid volume. I suggest using an accurate digital scale.

Important Note:
Make very sure to completely and thoroughly mix your fragrance oil in the gel! This cannot be stressed enough. Even when using the right kind of non-polar 170+ FP fragrance, it is still imperative that the oil be mixed in well to avoid any possible separation. Stir stir stir, for at least 2 full minutes! And when you think you've probably stirred enough, stir as much again just to be safe!

Where to get them:
I recommend buying fragrance oils that are specifically formulated for use in gel, and buying from only reputable sources. If a fragrance company does not specify their fragrances to be safe for gel, you will need to get MSDS sheets on them and determine the flash point, and then test them for polarity. Even if a company simply labels them "gel safe", be sure to question them on how they determined this, and verify that they have been tested properly. It is still a good idea to test a small amount from each new batch you get just to double check, even if it is stated as safe by the supplier. Manufacturers can make mistakes sometimes too and there can sometimes be variances in batches, so it's best to be responsible for the testing yourself and leave no doubts.