From: zetie@vax.oxford.ac.uk (The Edible Dormouse)
Newsgroups: rec.juggling
Subject: Coloured Flames - FAQ answer
Date: 22 Jan 93 15:08:58 GMT
Organization: Oxford University, Dept of Antiquated Physics

[Terry -- can you put this in the FAQ file under coloured flames please?
Thanks]
This is the base of a FAQ answer on coloured flames. I am inviting others to
send detailed accounts of specific colours to be inserted into the file which
also covers basic safety and use of the metal salts.


		Coloured Flames for Fire Torches

Many people have asked about this and many have played with coloured flames. On
the whole I would say from my experience that there is not a great deal which
can be done in this area by the amateur not willing to spend a lot of money and
time. For what it's worth here are my thoughts:

Colouring flame is done by dissolving salts (metal compounds such as sodium
chloride) in a solvent which also acts as the fuel. When the fuel burns, it
also causes the metal ions to emit on their characteristic wavelengths (just
like the flame colour tests in chemistry). To see the colour it is important
that the flame colour does not mask it.

Fuels
=====
The standard fuel for juggling is paraffin (kerosine) or lamp fuel (eg
Coleman's). See my file on torches and fire in the FAQ for more info.
Unfortunately the metal salts do not dissolve in these fuels which are mostly
short and mid-length alkanes and variants, as they are non-polar. You need a
polar fuel such as ethanol, which has the advantage of also producing a fairly
colourless flame. This is available as 'Meths' or 'Industrial methylated
alcohol' with impurities of no consequence (unless you want to drink it!). Be
warned that meths is poisonous. If ingested, drink milk of magnesia preferably,
but just water would be a good idea. If large quantities ingested, induce
vomiting. If splashed in the eye wash with running water immediately and seek
medical advice - meths is particulalry toxic to the optic nerve. 

Be especially careful when mixing - wear eye protection and thin rubber/latex
gloves.

Meths is more expensive than paraffin - about UK$2 per litre in early 1993 and
available from most chemists. Also the chemist may refuse to sell large
quantities - buy a few litres at a time.

Chemicals
==========
Start with the best - boric acid is cheap (about 5 pounds for 500g, enough for
20 or more litres of meths) and gives an excellent bright green colour.
Dissolve as much as will go into solution. Any precipitate can be dissolved in
more meths. Dip and burn as a normal club - remember to shake off excess
carefully. Boric acid can be obtained at chemists and through laboratory
supplies. It is a mild irritant but not especially dangerous.

Lithium chloride gives a gentle red colour. It is not a very bright flame, it
is expensive (more like 20 pounds for 500g when I last tried it) and more
difficult to get hold of - lab supplies again being the best option (I shan't
put addresses as they will differ for every country. post to rec.pyrotechnics
for a list of suppliers). Lithium perchlorate is a better red which also
sparkles a bit but it is very expensive (20 pounds for 100g) and quite
dangerous - irritant, and strong oxidising agent. It may be marked 'lab use
only' in some countries in which case you may be prosecutable under dangerous
substances laws for taking it to a public place.

Blue is nearly impossible to achieve as it requires a very cool flame. The mark
of a good pyrotechnician is his blue. Potassium acetate is wimpish and a poor
colour but cheap. Copper salts start green and only go blue briefly as the
flame dies away. Both are quite cheap.

[Please add more personal experience tales along similar lines here].

Use of Chemicals
================
They will nearly all destroy your wicks and clubs if mistreated. After use burn
off at least once in clean meths (with boric acid this gives a nice colour
still). Then burn with paraffin before storing. Preferably use them on cheap
props and home made toys of metal with easily replaced wicks.

Before use, clean the torch of paraffin by burning it as long as possible
without damaging the wick. The first one or two times the colour of paraffin
(yellow) will continue to burn with the chemicals, producing an eerie two tone
effect if you are lucky.

Have fun and be safe.

Ken Zetie (ZETIE@vax.ox.ac.uk)


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