Section 1.  GEL

Candle gel is made of 95% mineral oil, and 5% polymer resin.  This resin is a powder that, when mixed with the mineral oil, transforms it to a more solid state.  Very similar to Jello!
Penreco is the company that manufactures the gel and holds the patent on this technology.  This is the only brand of gel I recommend using because of it's quality and consistency.  Versagel™ comes in 3 types:  CLP (low density), CMP (medium density) and CHP (high density).
The thicker or more dense the gel is, the more fragrance oil it can hold.

Which type of gel do you need?
Well that depends on the candles you want to make.  For a plain, light to moderately scented candle, the CLP is all you need.  The CMP is a little thicker, and will hold more fragrance for a heavier scent.  The CHP is the thickest gel and will hold the heaviest scent load.  It is also the one you need if you plan to use any suspended embeds (such as glass fish, glitter, etc.).  The thicker the gel, the longer it takes to melt, and the harder it is to pour.  Remember that gel takes longer to melt than paraffin waxes, so patience is required.

Section 2.  EQUIPMENT

First you will need something to melt your gel in.  The double boiler on the stove method takes far too long with gel.  We've found that Presto Kitchen Kettles work perfect.  These are multi-cookers that you can buy at a local store like Wal-mart, for under $30.  They are black metal with a non-stick coating, so they are fairly easy to clean out.  They have a concealed heating element and a plug in temperature dial you can set to your desired temp.  You do not need water with these, you can melt the gel directly in the pot.  Use a glass (pyrex) measuring cup to scoop out the melted gel to pour into your candle jars.

You will also need a thermometer.  This is still necessary even though the Presto pot has a temp dial.  You need to be able to get an accurate reading on the liquefied gel.  I recommend a Digital Alarm Thermometer.  These have a metal rod you put down in the gel, and you can clip the thermometer box onto your pot.  Set the desired temp, and the alarm will beep when your gel reaches that temp!  This way you can go about getting your jars and wicks ready while your gel is melting safely.

For stirring the gel, you can use metal knitting needles.  You could also use a long metal or hard plastic spoon.  Do not use wooden spoons as they can add bubbles into the gel.

And never forget your safety equipment!  It is imperative to have a working fire extinguisher nearby at all times!  It must be the chemical kind, not the water kind.  Never put water on a wax fire, it will only spread the flames.  Sand or baking soda can be thrown on a wax fire also.  I recommend wearing safety glasses, a heat & liquid resistant apron, as well as gloves when making candles.  Better safe than sorry!

Section 3.  DYES

Most people use liquid candle dyes in gel because you want to maintain the gel's translucency.  It takes very little dye to tint the gel, so be careful... you can easily overdo it!  When making small batches and trying to get a very light tint, I suggest taking a toothpick and dipping the tip of it into the liquid dye, and then swirl it into the gel in tiny amounts until you get the color you want.  Sometimes even 1 full drop can be too much!  Solid forms of dye in a wax base, such as blocks or chips, may cloud your gel.

Section 4.  FRAGRANCE

This part is very important!  Please read carefully.  In order for a fragrance oil to be safe for use in gel, it must be non-polar, and over 170 flash point.  Non-polar means that the fragrance is miscible (will mix well) in mineral oil.  There is a way to test for this, and I strongly recommend testing any fragrance you plan to use before using it in gel.

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.

What is a flash point?

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.

Ideally, your gel candle should burn with a petite and steady flame.  Zinc core wicks are most commonly used and are easy to work with.  Gelwick™ is specially designed for use with Penreco's gel, and will burn well in containers up to 2.5" diameter.  Many people use standard zinc core wicks of various sizes depending on the container's diameter.  Many people are also using various other types of wicks such as paper core and coreless cotton wicks.  Gel burns slower and longer than paraffin wax, and does not produce as large of a melt pool as paraffin candles do.  Because of this, many people use a size larger than the standard wick charts recommend.  Sometimes in very large containers, you may find it tempting to use multiple wicks to achieve a large melt pool, but be aware that multiple wicks means multiple flames, and the more flame, the hotter the melt pool.  You don't want to get your melt pool temperature hot enough to come close to your flash point!  I would advise using a core container or inner glass in large containers instead of multi wicking.  In some containers this may not be possible, but as long as your gel candle burns sufficiently with one wick and does not drown out, then it's doing it's job.  I realize it's desirable to produce candles that melt fully to the edges and consume all of the gel, but when it comes right down to it, safety is more important.  If some of your candles leave leftover gel around the edges, it's not the end of the world.  Suggest to people to try scraping out the leftover gel and using it in their potpourri warmers!

Another thing to remember about wicking is the wax coating on most pre-tabbed wicks.  Many times this can melt off during pouring, and cause cloudy spots in your gel.  Some wicks may come impregnated with wax instead of coated, which will greatly reduce the chance of clouding.  Many times you can buy raw wicking by the foot which has not been waxed at all.  You will need to tab these yourself, but the advantage is that you can cut them to any custom length you need for your various containers.  When tabbing your own wicks, it is strongly recommended that you use a long neck wick tab, such as a 6mm or 10mm.  The longer the neck (or stem) the better, because it stops the candle flame from getting too close to the bottom of the container.  Many people have a bad habit of not reading caution labels and burning candles to the very bottom.  The problem with this is the flame gets so close to the glass and also makes the metal tab extremely hot, and can cause some glass containers to crack or shatter!  This is why it is so important to use caution labels on your candles, and educate your customers about proper candle burning and inform them of what could happen if they don't follow the instructions!

Section 6.  EMBEDS

It is critically important that only non-flammable items be used as decorative embeds in gel candles!

Section 7.  TECHNICAL INFO

Melt point -
Pouring temps -
Flash point -
Melt pool temps -

Section 8. TESTING YOUR PRODUCTS

Test your fragrances -
Fire test your embeds -
Test glassware for heat safety -
Test burn your finished candles -
Label your candles -

Penreco's Stance on Polarity Testing
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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.

Safe Gel Checklist: I use only certified Penreco Versagel™ (U.S. Patent No. 5,879,694). I use only Fragrance Oils with a flash point over 170° F.  I use only Non-Polar fragrance oils & each batch is tested for polarity.  No more than 5% fragrance has been added in Medium & High density gel, and no more than 3% in Low density gel. The fragrance oil has been mixed in VERY thoroughly.  I use only heat safe glassware or containers that have been safety tested. I use only wicks with an extended neck length of at least 6mm or 10mm. I use only non-flammable decorative embed items in any part of the gel that could come in contact with the flame, and these embeds have been safety tested. Any possibly flammable objects are protected by an inner glass and cannot come in contact with the flame. I label each candle with the proper caution labels. Each new batch of candles is thoroughly test burned for safety before being sold.