Help with basic chemistry (coloured fire)

[MixxyMatosis]

I'm getting the kit together for a photography project using long exposures and fire.

http://www.diyphotography.net/how-to-create-a-wall...

But I would like to modify the colour of the flame if possible. I'm using methylated spirits as the fuel at the moment and I know various chemicals copper, salt borax etc.. give a variety of colours.

My my question is this: How can I make a dissolvable additive to add to my fuel to change the colour it burns? I've had a good google about and come up empty. I know it's possible as I found you can buy additives but it must be easier and cheaper to make them at home.

Thanks in advance.

[fourfoldroot]

Household salt-orange.
Ground magnesium-white (may burn quite well)
Ground up lithium tablets-red

[thegherkin]

Wikipedia has a good article.

http://en.wikipedia.org/wiki/Colored_fire

Of course, you may have to play about with different fuels to make sure the salts are soluble.

[MixxyMatosis]

I have that wiki up at the moment. Nice list but it doesn't really tell me how I can dissolve them in meths though. I've chosen meths after testing a few fuels to find the one that burns the longest with the least damage to the hessian strapping I have.

[thegherkin]

MixxyMatosis said:

Nice list but it doesn't really tell me how I can dissolve them in meths though.

Well, if the salt you're after isn't soluble in the fuel you want, there isn't much you can do. It's like me saying I want to use water and barium carbonate ... except barium carbonate is insoluble in water.

You have to fiddle about with different fuel mixtures to make it dissolve, or find a different chemical.

[MixxyMatosis]

thegherkin said:

Well, if the salt you're after isn't soluble in the fuel you want, there isn't much you can do. It's like me saying I want to use water and barium carbonate ... except barium carbonate is insoluble in water.

You have to fiddle about with different fuel mixtures to make it dissolve, or find a different chemical.

Right ok I think I see what you're getting at. After more googling I see someone saying that alot of the chemicals that change the flame colour will dissolve in isopropyl alcohol. Does this seem a reasonable suggestion?

[V8LM]

Look at the solubility of metal salts. This is solubility in water - http://en.wikipedia.org/wiki/Solubility_table - find the salts that are most soluble in water (metal hydroxides, iodides, nitrates) and then check their solubility in ethanol. Those soluble in ethanol should be sufficiently soluble in meths.

Potassium hydroxide - purple, sodium hydroxide - yellow, copper nitrate - green. Look here for some indication of the colours - http://en.wikipedia.org/wiki/Flame_test

[Flibble]

MixxyMatosis said:

Right ok I think I see what you're getting at. After more googling I see someone saying that alot of the chemicals that change the flame colour will dissolve in isopropyl alcohol. Does this seem a reasonable suggestion?

Most of those will probably also dissolve in meths (being a fairly similar alcohol), alternatively you could just burn them in isopropanol; it's cheap and burns well.

[Shaolin]

Meths dissolves most of what you will need to dissolve.

If you're feeling adventurous you could put them in some sort of squirty bottle for an impressive flash of flame, I've only ever tried this using a bunsen as the flame and then squirting the bottle contents across it but suspect a candle or spirit burner would do just as well, careful not to kill yourself or burn the house down though (it's not that dangerous, but do be careful).