Violet flames are very easy to make. All you do is sprinkle salt substitute on your fire. Salt substitute contains potassium chloride and potassium bitartrate. If you are familiar with the emission spectra from flame tests, you'll recognize that potassium salts burn violet or purple. To me, the color seems more of a blue-violet, but you can get a more reddish purple if you mix a little strontium from the red fire tutorial in with the salt substitute.
Keep in mind, violet is not one of the colors your eyes see really well. The subtle glow of these flames can be completely overwhelmed by the colors from trace impurities. This means two things:
- Use as pure a fuel as you can. I used Heet™ fuel treatment, which is methanol. If you sprinkle the salt substitute on your wood-burning campfire, the flames will change color but the color won't necessarily be violet.
- Use salt substitute and not lite salt. Lite salt is a mixture of normal table salt (sodium chloride) with potassium salts. The yellow from the sodium will overpower the violet from the potassium.