The colors will be purer if you use ethanol (denatured alcohol, 190 proof Everclear or equivalent) as fuel. High concentration isopropyl alcohol has a yellow tinge to the flame from soot formation. Methanol (sold to the public in the US in convenient small bottles as Heet Gas-Line Antifreeze) is also very good and may be easier to obtain in some areas than pure high-proof ethanol.
Sodium chloride, lithium chloride, copper chloride, and boric acid give the most intense colors. But sodium chloride's orange-yellow color is a bit boring compared to the others.
A few milliliters of the alcohol mixture can be ignited in a shallow stainless steel dish with relative safety and there will be no color interference from carbonaceous fuels yellowing the flame via soot.
If I had to pick just one to try, I'd suggest boric acid. The green flames it produces are unlike any "ordinary" fire and boric acid is easy to find. Here's a short video with a good view of how the flames look: https://www.youtube.com/watch?v=g1jHVk6oqjU
The first night that my now-wife met me in person, I showed her colored fire like this in the fire pit at my apartment complex. She originally meant to visit for just a few days but we've now spent 21 years together. I'd say that the demonstration was a success.
I don't think there are any combustion reactions here (besides the source flame), since these are already fully oxidized salts. It's only internal electronic transitions of the metal ions.
Not my area of expertise but I believe the explanation is: the radiation profile is blackbody radiation proportional to the heat of the flame. The metal salts color the flame by absorbing light and re emitting it according to their electron transitions. However the don't add additional energy so there will be no UV light, since the original flame doesn't produce (almost any) photons that energetic. Magnesium burns much hotter and emits uv directly from blackbody profile.
One of the magical experiences growing up, with my mom working in a food safety lab, was playing with the different coloured fires (and the pipettes of course).
I only later learned about spectrometry: roughly, the flame's light is split into a rainbow with a diffraction grating and the colours become a barcode for the chemicals that burn.
"If you use alcohol as a fuel, please remember that it is much more flammable than wood. Never add alcohol (or any liquid fuel) to a burning fire, or it will react much [like] lighter fluid"
This should be at the beginning of the article, rather than the end. People have suffered severe burns on multiple occasions from doing the "rainbow fire experiment" and adding alcohol directly to the flame.
i add alcohol directly to flame all the time, and even burn it on my skin. there are real risks to be careful of, but i think you are exaggerating them
alcohol is great for this kind of thing for several reasons:
- you can extinguish a spill with water
- its low boiling point protects your skin and other materials from high heat, but only when they are wet with it
- you can mix a little water into it to enhance this surface-protecting effect
- unlike many organic solvents, its toxicity is quite low (ethanol and isopropanol, not methanol)
- it produces very little carbon monoxide or soot
that said, it can still spread fire quite far quite fast, and a house fire can go from the size of a small campfire to deadly flashover in under a minute, so be very careful
I’m thinking of producing an “Alchemy Set” for kids. Like a chemistry set, but… more esoteric. I work with these experts in Alchemy from the Embassy of the Free Mind in Amsterdam.
If you are into this sort of thing, any experiments you’d hope to see in the set?
My daughter (6) loves experiments, but honestly all the chemistry sets and similar we've bought have been quite boring, except for the bog standard baking soda/citric acid/green coloring snot volcano.
I like chemteacherphil on YT, who does a lot of visually fun experiments, many involving fire, and I would definitely buy packaged products of some of those, instead of trying to source chemicals/metals/tools for home (not having access to our own lab).
My nephew is into this. The great thing about the bicarb style ones is that he can actually play with the ingredients. And this is what "experimenting" should be. Trying things out and seeing what happens. The fun is finding out what happens when you use the kit in an unexpected way and make a mess on the ceiling.
The problem with the more exciting/interesting experiments is that play has a larger potential blast radius. And understandably adults impose more limits which then leads to less actual experimenting. And that actually makes it less fun.
Because the best experiment is to start with random chemicals and seeing what happens. Not a carefully curated set with predictable results. The boring failure and the unexpected result are all part of the fun.
> My daughter (6) loves experiments, but honestly all the chemistry sets and similar we've bought have been quite boring [...]
I had chemistry sets as a kid, and I think I agree with this. As an adult I understand why these sets are boring, and honestly I'd be more likely to play with these sets as an adult. The instructions and guides weren't really very creative and they weren't engaging.
At the same time, the chemistry sets of the (for example) 1950s were absolutely batshit insane and are rightfully taken off the shelves.
It's a shame there isn't much of a middle ground other than finding YouTube demonstrations. Then again I haven't looked for a chemistry set lately...
Sodium chloride, lithium chloride, copper chloride, and boric acid give the most intense colors. But sodium chloride's orange-yellow color is a bit boring compared to the others.
A few milliliters of the alcohol mixture can be ignited in a shallow stainless steel dish with relative safety and there will be no color interference from carbonaceous fuels yellowing the flame via soot.
If I had to pick just one to try, I'd suggest boric acid. The green flames it produces are unlike any "ordinary" fire and boric acid is easy to find. Here's a short video with a good view of how the flames look: https://www.youtube.com/watch?v=g1jHVk6oqjU
The first night that my now-wife met me in person, I showed her colored fire like this in the fire pit at my apartment complex. She originally meant to visit for just a few days but we've now spent 21 years together. I'd say that the demonstration was a success.