All About the Gel
We at the Chemistry Store do not manufacture candles and we are not experts in the field of candle making. Before you make gel candles we have prepared a list of criteria and safety factors that you must consider before you make your candles. This list is a broad outline and does not cover every factor in making gel candles. We can not stress enough the need to perform strict safety tests concerning the burning and flaming characteristics of any candle. The Internet contains a great number of informative  sites as well as E-mail lists that have discussion groups to help you learn to make these products safely.
The following information that we provide is based on information we have taken from the  Penreco Corporation, our experience and information gathered from the net.   Our products contain the Versagel C Series of gelled hydrocarbons. Versagel is a trademark of the Penreco Corporation.  US Patent 5,879,694.
Candle gels are manufactured from a specially selected and processed mineral oil. They are gelled with copolymers that give them a clear rubbery texture. These products are formulated with a narrow cut hydrocarbon oil of exceptional safety relative to the flash point. Penreco also has optimized polymer type and concentration to produce a gel of exceptional clarity and maximized viscosity to resist cold flow of the gel in the container of choice.

The MP grade is the most popular among the candle makers.  It is difficult to predict which will work best for you, so in your initial trials you might want to bring in some MP & HP gels. Some candle makers use different grades in their pour to produce certain layer effects. HP Gels are better for shipping since they have less a tendency to flow. This is important in hotter climates.

Melting Your Gel: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.

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.

Temperature Chart

Please note that these temperatures are estimates only, and may need to be adjusted by as much as 10⁰ C
The inclusion of fragrance or other materials will affect the properties listed above.
These temperatures may need to be modified depending on the flash points of the added ingredients.

Equipment:
We have seen all sorts of methods to melt the gel. Forget using the microwave, it just doesn't respond well to microwaves.
Crock Pots, Presto Pots, Glass Pots and metal pots can be used. You may heat the gel in a pot on a very low flame. THIS MUST BE SUPERVISED AT ALL TIMES! An electric hot plate will also work well. Glass pots are great to use. You'll  be able to watch  the gel as color is added. Your best bet is to have a pot or glassware that has a pouring spout. You have less spillage when pouring into your containers or glassware. If you don't have a spout, a ladle can be used.
Get yourself a thermometer that reads in the ranges in the table above. This will allow you to be consistent with your pours and special effects you may try to achieve as you master the art.
Make sure the area that your pouring your gel is steady and level. Gel like water will seek its own level and with an uneven surface the gel will harden lopsided in your candle. Select an area that you don't have to move your newly poured candles for an hour or so.
Just a Safety Note: Candle Gel will burn when hot enough (Aprox 230 degrees F). Always keep a fire extinguisher handy. It should be in your kitchen anyway! While we are on this topic of safety,  please remember you are working with some very hot solutions. These solutions can scald or burn skin. Protect your eyes and skin against splashes. Keep small children, pets and annoying people away from your work area. If you should get burned, treat it like any other burn  and of course if you should get some in your eyes or enough of burn on your skin, see a doctor immediately.

Candle Containers:
Glass containers are the best to show off the beauty of candle gel. A lot of the fun is shopping for unusual glasses to use, such as wine glasses, mugs etc.  However, this certainly does not rule out using metal , clay or even seashells to hold your gel. Plastic or wood containers should not be used.
The glass you select must be able to withstand a hot pour of candle gel. Tempered glass is best. You certainly don't want to take your glassware out of the freezer and pour into it. Pre-warming the glassware will help prevent stress on the glass as well as cut down on the amount of bubbles in the gel. In addition you should select glassware that is stable and not easy to tip. The base of the glass should be such that it will not present a problem if the gel is burned to the bottom the glass  (Although you should mention in your instructions never to burn the bottom 1" of the candle!).
The use of very narrow glassware should also be avoided. Besides potential blackening of the glass from candle combustion, a factor that is known as gel pool comes into play. This is the area around the candle flame of melted gel. Too much or too little of a pool will cause incomplete combustion which creates a lot of smoke. Mouth openings should be 2 to 3 inches at least. Glassware like coffee mugs, beer glasses, ivy bowls and votive glassware can be used.

"Tiny Bubbles...."
Bubbles fall into two categories, wanted and unwanted. Often time bubbles are wanted in candles such as champagne glasses or other bubbly beverage designs. More often you want to get rid of them. Hotter pours are generally the answer. Preheating or warming the glassware you pour into helps. Keep an eye on the the items you embed or add to the gel. Often they will produce bubbles as well as some wicks.  We will discuss embedding and wicks  later. When working with the gels try to use metal rather than wood spoons. Wooden objects tend to cause bubbles. (Scientists all over the world are working on that problem now!). Pour gently down the side or from a close distance, much like pouring a beer to avoid getting a big head of suds.
In a recent discussion we have heard that heating the gel to a clear solution with no lumps and then allowing to cool to just before it becomes too stiff to pour also is a way to minimize bubbles.
As your gel is hardening, if there are any surface bubbles break them with a pin. A heat gun is excellent from re-warming the surface. Even a lighter can be used to touch up or smooth  the surface.
If you have more bubbles than you want, warming the candle in your oven (131-158⁰ F) for several hours will help. Those who live in hot climates can let them sit in the sun.
On the other hand if you want bubbles, pour at lower temperatures. For the frosting effects you can even whip it. For those who want to make beer candles, paraffin wax is often used to top the gel. Whip the paraffin wax and pour over the top of your gel. The head will be more stable.

FRAGRANCE
We provide a line of fine fragrance oils (GELESSENCE)  that are especially formulated for gel candles. If nothing on our list strikes you fancy, there are a multitude of fragrance houses on the net that will sell little to large quantities of fragrance. You must specify to your supplier that you are looking for fragrance to be used in gel candles. If you currently making wax candles, often times your fragrances will work. Use the mineral oil test listed below.
A gel candle fragrance will remain clear when added to your candle gel. If your gel is cloudy your fragrance may not be right or you may have added to much.
The amount of fragrance you want to add to a gel should be no more than 5%, with ranges of 1-3% being the best. If you want to make fragrance gels, we have a gel that is designed just for that purpose and will hold up to 10% fragrance oil. (Fragrance Gel) 
Another Safety Note!  Fragrance in gel candles has probably been the major factor in recalls and candle problems. Test your fragrances well by burning some test candles. Also allow them to sit on the shelve for awhile, we have seen some fragrances migrate to the surface over a period of time and cause uneven burning.

The Technical Side to Fragrance
Fragrance selection becomes critical as it relates to compatibility or solubility in the gel. A fragrance with a non-polar (hydrocarbon compatible) character is most preferred. This non-polar character does not deteriorate the gel strength and has excellent solubility. 
The second variable in fragrance selection and extremely important is the fragrance's flash point. Most fragrances have flash points of 140⁰ F and higher. A preferred fragrance flash point would be 170⁰ F or higher. A quick check for fragrance polarity can be done with mineral oil. A non-polar fragrance should be 100% soluble (with no separation) in mineral oil at the following ratios:
25% fragrance/ 75% Mineral Oil
75% fragrance/ 25% Mineral Oil

DYES AND COLORS
No information has been found which shows that dye influences candle safety. The selection of dye does depend on its solubility in the gel. Candle dyes will work well. Food Dyes, which are water soluble, do not mix with candle gel.
Working with dyes is where some real creativity comes in.  We have seen some crafters pour different color gels into molds, like heart shapes or cubes using High Polymer gel and dying them various colors. Allow them to harden.   Take these shapes, place them in your candle and over pour them with clear Medium Polymer  gel. 

PROCESSING & MIXING
Care must be taken in not only selecting the correct fragrance but also  in completely and uniformly mixing the fragrance into the gel before packaging the gel into the container. Incomplete mixing of the fragrance can cause an irregularly burning flame, and clouding of the gel. Stir thoroughly but avoid trapping air into your gel.
Add your dyes and fragrances just before your ready to pour. You really want to keep the amount of fragrance exposure at the higher temperatures down to a minimum. 

EMBEDDING:
One of the most interesting aspects of gel candles is the ability to embed all sorts of objects in the gel with some absolutely stunning results.
Rule #1 - The object that you want to embed should not be able to burn or smolder. Plastic and wood objects are a no-no. Items made from glass such as marbles, crystals, seashells, metal and gravel work well. We have heard of precious stones and rings being imbedded in wedding candles.
Before imbedding objects we recommend you dip them in some candle gel to put a thin film on them and let harden. This will help prevent the objects themselves from causing bubbles as they are placed in the gel.
Try to keep the objects you embed towards the side and bottom of the container away from the wick, so it does not interfere when the wick burns. It also tends to keep the object more visible. If you are making a bottom layer from shells or pebbles, particularly sand or gravel, try to avoid dusting the inside of the glass. Wipe the glass clean if this happens.
There are several methods of embedding objects. One method is like working with quick sand. This method you learn by trial and error. Waiting for the right time is very important.  Depending on the temperature you started with and the weight of the object you want to embed,  wait to the gel begins to set or get sticky. Place the object on the surface and allow it to sink into the gel. (Remember if you don't like what you get, start all over and reheat the gel.).
Another method is to pour in layers. Allow the surface to skin or semi-harden, place your object and then over pour.

GEL CANDLE WICKS
We do not sell wicks but recommend you look at many of the sites on the internet that provide all types of wick materials to the hobbyist trade. Wick sizes are diverse and must be test burned to make sure they work with the gel and additive combination. Different sized containers and additive combinations (colors, specialty pigments, fragrance load, etc) can affect how the candle will burn. Cotton and paper cored wicks are generally not used in gel candles, whereas zinc cored wicks stand straight in hot gel during manufacture and burning. a good starting point would be a 51-32-18 zinc core wick.  Wick length and placement are important details that can contribute to candle safety. Wicks should be trimmed to less than 1/4 inch above the gel surface. Large wicks create a potential  for a very large flame with non-uniform combustion, which, when not placed properly, can create localized overheating of the container and "pool". Such conditions can cause uneven temperature dissipation, a potentially unsafe condition.
Pre-tabbed wicks which prevent the wick from going to the bottom are the best. Adding a base such as gravel, glass beads or shells will hide the tab.
Some wicks come with a coating of wax on them. this coating will sometimes cause bubbles in the gel.  It is best always to give your wicks a light coating  or pre-coat of gel to help prevent that.
To secure your wick to the bottom of the candle, dip the tab in some gel and press on the bottom of your container. We have also heard of using a little hot melt glue on the tab to secure it to the bottom.
Place your bottom decorations around the base of the wick.
On very large candles or for design effect, multiple wicks can be used. One wick should be used for every 3 to 4 inches of candle diameter.

CONSUMER USE INSTRUCTIONS
Always make up a little card or sticker to put on your candle with this information:
Never burn a candle unattended
Never burn for more than four hours
Always trim wick to 1/4 inch above the gel surface before use
Never burn the last inch of a candle
Keep out of reach of children