What Kind of Candles Work "Best"?
There are lots of different kinds of candles in the world and as long as they are in an appropriate container (steel, glass, ceramic) and "fit" under the radiator assembly (without being too close) they will probably "work" -- the thermal energy of the candle flame will be converted into dry radiant space heat by the radiator assembly. But some candles do this better than others. And Liquid Candles are "better" than Solid Candles, but let's discuss Solid Candles first.
General guidelines, the "harder" the wax the higher the grade and the "hotter" it will burn (and produce less soot). The larger the wick (in diameter) the larger the flame and the "hotter" (and faster) it will burn. The "purer" the wax (fewer contaminates) the cleaner the burn (less soot is produced).
Coloring agents are "contaminates" (for this discussion), they do not "add energy" to a candle and may not burn well. Darker candles tend to have more coloring agents than lighter candles and produce lower temperature flames and more soot. Scented candles are similar, but vary greatly depending on the chemicals being used to produce the scent. (Aromatic oils are best, they at least "burn" in the flame.)
The "Best" candle then, would be a harder wax, white (or very light), with a medium wick, unscented, or maybe scented with orange/lemon oil in an appropriate container.
The 3 inch "Dollar Store" jar candles work very well for the money. They are usually a medium grade of wax, have a medium wick, and can often be found in very light colors and lightly scented. The picture shows a "Dollar Store" very light yellow "Energy" scented candle. The flame is an inch (or a bit more) in height and has a "full body". Please note that the thermal energy (heat) radiating downward from the radiator assembly has melted almost an inch of the wax! Do Not Move a Kandle Heeter™ Candle Holder When Burning!
"It is commonly believed that the candle made of beeswax burn more cleanly than petroleum based paraffin waxes. However highly-refined paraffin wax can burn as or more cleanly (with regards to particulates created during combustion) than natural waxes. The type of wick and inclusion of any scents and/or dyes have a much greater impact on the release of compounds, particulates, and smoke, regardless of the base material. The cleanest burning candle will therefore be unscented, un-dyed, and a well constructed candle burning in a draft free area. " (Wikipedia -- http://en.wikipedia.org/wiki/Candle)
A Note on "Size". The candle flame needs ample oxygen to burn well (and cleanly). Always insure that there is at least an inch between the top of the container (not the top of the candle) and the lower lip of the radiator assembly. If the top of the container is too close to the radiator then ample oxygen will be unable to reach the flame and the candle will burn sooty and poorly.
Do Not Allow Soot to Build Up Inside the Radiator Assembly!
Soot is a by-product of incomplete combustion (not enough oxygen, low temperatures). Soot is trapped in the interstices of the radiator. It can easily be rinsed out, but then the radiator will need a 6-8 hour burn to be dried out. The soot is easily brushed out with a 1" pastry brush, or it can be vacuumed out. DO NOT BLOW IT OUT WITH YOUR BREATH -- YOUR FACE WILL BE INSTANTLY BLACKENED AND YOU COULD EASILY GET SOOT INTO YOUR EYES.
The photo is of a Radiator that had been burning many evenings over several weeks. It shows a "light dusting" of soot and does not need to be cleaned. But this soot would have been deposited on the ceiling if it had not been trapped within the Radiator. Better candles produce less soot. Check your radiator weekly to get an idea of how quickly soot is building up.
Liquid Candles are Better than Solid Candles!
Some restaurants use liquid candle "cartridges" on their tables to create ambience. These candle cartridges burn 99% pure liquid paraffin with no odor and virtually no soot. They are available in several different "sizes" based on their estimated burn time at restaurant supply stores. Pictured below is a "50 hour" liquid candle cartridge.
The flame is perfectly positioned within the Kandle Heeter™ Candle Holder and more importantly, the flame never goes lower! These cartridges have "drawing wicks" -- they draw the liquid fuel up to the flame. The liquid goes down as they burn, but the flame always stays at the top.
99% liquid paraffin is about as pure as you can get. These candles typically burn "hotter" than solid candles and drive the radiator assembly to higher temperatures, usually around 180-200 degrees Fahrenheit. And since the flame never "sinks" the temperature stays constant.
No Odor and No Soot. And they are reasonable priced (at least they were last year). Our local restaurant supply store carries these Candle Cartridges (trade name "Soft Light", manufactured by Candle Lamp Company) in 6-packs for less than $15. That is 300 hours of burn time, or approximately a full month of burning at 10 hours of burn a day.
There is one major drawback. These cartridges are not refillable! Once used they are meant to be tossed. I have not been able to find a way to safely re-use these cartridges. The wicks must be pulled out and the plastic recycled.
Yet all is not lost, there is an even BETTER Liquid Candle!
These are small glass decorative wicked refillable containers designed to burn 99% pure liquid paraffin. The ones I have found come as "gift sets" of two candles with a small bottle of paraffin and a little funnel. I think the wick is fiberglass. Cash and Carry (our local restaurant supply store) also sells gallon containers of 99% pure liquid paraffin very reasonably, so after the little bottle is empty, you can easily buy more fuel. Always be sure to buy 99% pure "lamp oil" -- lesser grades are very odoriferous.
These refillable candles burn very nicely, the size is very good, and there is no plastic to recycle. Since there are two of them in a set, one can always be full and ready to go while the other is burning away.
There are several sizes of these "candles" so just be sure it is an appropriate size for the candle heater. Remember the goal is to get the flame into the ideal "hot" zone, about an inch below the lip of the radiator. Keep the flame height "small" to avoid soot build up.
I found this gift set at Michaels.
So, there you are. Probably more information about candles than you wanted or expected, but that is pretty much the sum of what we have discovered in the past 4 years of living with Kandle Heeter™ Candle Holders. I keep one in the front room that burns 99% pure liquid paraffin and one in the bedroom with a 50 watt Infra-Red Lamp that is on all night long. 50 watts is about a nickel a night for enough heat to keep the damp cold night air outside where it belongs.
Please let us know what you discover. You can always drop us an email at vegalot<at>gmail<.>com.