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I am a martial artist who uses fire weapons in my shows. I am wondering how I can get the flames to be different colors.

I've done some research about it, and have found that the salts of some metals can be used for the intended purpose (for instance, copper sulphate burns green).

However, I use kerosene as my fuel and am wondering if it is advisable to mix the chemicals with it (kerosene) without burning myself. Also, I would like to know how to obtain the chemicals and what amounts should be added to a given volume of fuel.

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I've done some research about it, and have found that the salts of some metals can be used for the intended purpose (for instance, copper sulphate burns green).

You're right! Various melts salts are known to colourize a flame. In the lab and/or for demonstration purposes, this is typically achieved by holding a magnesium oxide stick with a bit of the salt attached into the flame of a Bunsen Burner. There's a wikipedia page on Flame tests that shows some possible effects.

I use kerosene as my fuel[…]

Here's a problem. The salts you could use soluble in water, but insoluble in a solvent as unpolar as kerosene! Consequently, you might want to give a flammable, but more polar solvent a try.

Is it conceivable to change the flammable solvent used in your performances? I reckon that you might achieve the desired effect using ethanol or methanol. With respect to the toxicity of both solvents, I'd definitely try ethanol first!

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First, to produce color flames you don't want kerosene. Kerose produces bright flame, while to get a colored flame one need a fluid that produces a colorless flame on its own. I recommend ethanol, preferably dry.

Second is colorant. Lucky for us some strong colorants dissolve pretty well in ethanol. Specifically, green colorant tryethylborate is mixible with alcohol and actually burns on its own. Copper chloride (bluish colorant) Lithium and Calcium chlorides (red colorants) dissolve in ethanol fairly well. Yellow is pretty easy to get, even small addition of sodium salts (such as table salt) gives a bright yellow flame. It is actually a problem, as minor impurities of sodium may contaminate other colors with yellow.

I highly recommend to perform with colored flames only at open air. The substances I mentioned are slightly toxic and would form smoke on burning.

Unfortunately, there is no viable violet flame colorant (violet is usually produced as a mixture of blue and red), and bluish colorant (copper chlorides) cannot produce flame that is bright and saturated at the same time.

To my knowledge, the compounds I mentioned are all purchasable online. While some of them are toxic, none of them is really dangerously so. Breathing in the smoke, though, is unadvised, as well as drinking the solutions.

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As others have mentioned, kerosene is not the best solvent for the purposes of dissolving salts. Methylated spirits (denatured alcohol) is probably the best, and possibly rubbing alcohol, to give you the desired solubility you want. Caution - alcohols have a much lower flash point, are easier to ignite, are more flammable, harder to extinguish than kero, and burn with almost undetectable flame. They pose a significant flammability risk, especially if you spill some. You need to weigh these risks up for your performance, and seek some advice from your industry if you have not worked with these solvents before.

You can also consider pre-treating your implements by soaking them in the solution of desired chemical and allowing the solvent to evaporate (possibly for some days) and leave behind impregnated salt, which can then be burnt using other fuels. I have seen this done with pine cones soaked in aqueous solutions and allowed to dry out before being added to a campfire. You would still suffer from the competing flame colour and intensity of your chosen fuel. The colour of a kerosene flame will still probably dominate the subtle colours of your additives.

As for quantities; this will depend on the solubility of the salt in your solvent, and the general rule will be 'as much as dissolves', but will depend on the salt you are using. For instance, the solubility of sodium chloride (yellow flame) in ethanol (and therefore similar to methylated spirits) is less than 1g per litre, while lithium chloride (red flame) dissolves at something like 250g per litre. There are a couple of very good articles about the ins and outs of coloured flames for performance here:

Each different flame colour uses a different chemical which in turn has its own toxicity and undesirable residues that need to be considered for your own health (in preparing and performing) and also your audience (who may be breathing the stuff in). Be sure to read and understand the SDS of the chemicals you are using BEFORE you purchase and use them.

Fire colourants and additive kits are available for fire performers, and there are lots of very good sources on the internet for you to purchase and get advice for your performance:

http://www.homeofpoi.com/shop/productDetails/Pack-of-Colored-Flame http://www.threeworlds.com.au/colour-flame-dye

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