Wick Selection - 6 Easy Steps Excerpted from Candle Making By Bob Sherman

The vast majority of candle making questions involve wick size and selection. So much so that I have written more articles about it for this site than any other topic. In the ever changing world of candle making, I have once again evolved a method for wick selection that is simpler than what I have previously used. The full version was included in the wick chapter of my book - Candle Making, A step by step guide from beginner to expert. Here I present the most useful portion for your benefit.

Six Easy Steps To The Right Wick Size
In the past I have jokingly given the following response when asked how to choose wick: take into account the wax, additives, scent, color, mold size, time of day, phase of the moon, and price of tea in China - then take your best guess. Eenie meenie miney mo is about equally effective. With time and experience you will spend less time pondering about the correct size wick.

I have been following the technique discussed here for many years without giving it much thought. In response to a lot of begging from my candle making students, I sat down and put all those things I had been doing unconsciously into a system that can be taught.

Since each component of a candle affects every other component, every change will affect the wick size needed. Accordingly every different formula or candle size will usually require a different wick size. As mentioned in the materials chapter, it is common for materials from different suppliers to have somewhat different properties.

1. Choose the correct type of wick for the candle. Cored wick for containers, votives, and floating candles. Flat or square braid for molded candles and tapers. The different wick types are discussed in detail in the Materials chapter
2. Wick suppliers generally publish guidelines for their wicks in their catalog or on the packaging. Wick size guidelines usually give a range of candle diameters for that size wick using paraffin wax. For example 3 inch to 4 inch diameter. If using a soft wax formula this wick would be a good starting point for a 3 inch candle, or a 4 inch candle using a harder wax formula. Softer wax requires a larger wick than a harder wax in the same size mold. This will be our base size for experimentation.
3. Using the wick selected make a test candle. Allow to cure fully. As a rule candles should not be burned for at least 24 hours after making them. If you want to really be professional about it, make at least three test candles. One with the size wick selected, one with a size larger, and one with a size smaller.
4. Burn the test candle. The bare minimum time for a test burn is one hour per inch in diameter, however an 8 hour test burn is usually more enlightening. It is important to keep notes about the wick size, burn time, size of the melt pool, and any problems such as not staying lit or smoking.
5. Analyze the results of the test burn. Ideally we are looking for a wick that consumes wax at the same rate it is melting it. This will give us a nice burning, dripless candle that throws fragrance well. If it burns well and exhibits no problems then you now have the correct wick for that formula in that size mold. Otherwise refer to the following:
    
   • Wick goes out - Usually a large melt pool accompanies this. A very good indication that the wick is too small and is melting wax faster than it can wick it up.
   • Wick sputters - Usually this is accompanied by little or no melt pool. A very good indication that the wick is too large and is wicking up wax faster than it can melt it. The flame running out of fuel causes the flickering or sputtering.
   • Candle drips - This is usually an indication that the wick is too small. The wick needs to consume the wax at the same rate it is melting to have a dripless candle.
   • Carbon buildup on wick - This is common with cored wicks since they do not curl into the flame. A small amount of carbon is unavoidable, but large amounts indicate that the wick is too large. This is also called mushrooming.
   • Candle produces excessive smoke - This usually indicates that the wick is too large.
   • Wax does not melt all the way across - This is most common in container candles. Although sometimes a smaller wick will correct it, often the problem lies with the wax. If you cannot improve the burn with a different wick, try a different wax formula.
      
6. Repeat steps 1 through 5 with the change in wick size indicated above. By using this process of elimination we can usually obtain a good burning candle after one or two test burnings. It is important to keep your wax formula the same throughout the testing.

Although it is not common, sometimes you will encounter a situation where none of the test candles burn well. This generally means that your wax formula / candle size does not match any currently available wick. In a case like this you will need to modify your formula to make it either softer or harder. The easiest way is to add a little more hardener, because the only safe wax to make it softer is to use a lower melting point wax.