Re: Freezer spray
There really isn't anything complicated about these sprays and no magic ingredients are needed. Purified butane (cheap to produce) will work as well as anything and won't leave a residue. They all rely on the temperature change that takes place when a pressurised or liquefied gas is released from that pressure as described by 'the ideal gas law', sometimes called the 'general gas equation'. Messrs Boyle, Charles and Avogadro did the hard work. The effect is readily demonstrated by releasing air from a car tyre whereupon the resulting stream of air feels cold. Physics lesson over.
Alan
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