so i know that When you light a candle, the heat of the flame melts the wax near the wick. This liquid wax is then drawn up the wick by capillary action. The heat of the flame vaporizes the liquid wax (turns it into a hot gas), and starts to break down the hydrocarbons into molecules of hydrogen and carbon. so the wax is whats burning as the fuel. so if i mix borax or strontium nitrate into melted candle wax, would the candle automatically burn red or green?
also would borax or strontium nitrate overpower the smell of the candle?
I encourage you to be a scientist and experiment to answer your own hypothesis. It could be that no one has ever done exactly what you ask so they are unwilling to answer you.
The vaporized wax burns (is oxidized) to give water and carbon dioxide, not hydrogen and carbon.
Adding inorganic salts to the wax will cause a change in the color of the flame. I don't know about the odor caused by the salts, but there is very little odor coming from the candle unless it has some fragrance built in.
Robert Coots is correct that the wax burns to give water and carbon dioxide. A simplified equation is
(CH2)n +1.5nO2 --> nCO2 + nH2O
Small amounts of heteroatoms like Boron or metals like Strontium will alter the color of the flame.
Borax and the Nitrate in strontium nitrate are oxidizers that can replace the oxygen in the equation above. If you mix enough oxidizer into the fuel (paraffin) it will burn without oxygen and you won't be able to put it out. Solid rocket motors work in this way with ammonium perchlorate as the oxidizer.
Most of the candle smell is unburned fuel. The salts will not alter this unless you add enough to change the primary combustion.
When I ran the R&D lab for a candle manufacturer, we tried this with a variety of salts. In theory it should work. The real problem came from the salts clogging the wick and preventing the fuel from getting to the flame.
I applaud your curiosity, but you'll need to adjust your combustion equation a bit...carbon and hydrogen are separated in the combustion, but are not free elements; they merely combine with oxygen, separately. Also, you'll need to find some metalloorganics to make this work for any time worth your effort. Water soluble salts are not likely to do much for too long. Look in the CRC or Merck Index for decent solubility in non-polar hydrocarbons like benzene, pentane, hexanes, etc. But if you try this, be careful to only try a tiny amount and use proper protection...goggles, gloves, lab apron. It'd probably be best to run an idea by this group, first...
Mixing a nitrate with candle wax might be dangerous, especially if the wax is already molten. If you want to try it, start with a very small amount and do it outside on something that is not flammable.