Flash Powder

dmcfarlane

New member
A recent conversation with Alan Fincham produced a photo of Gaping Gill-Main Chamber, taken in the late sixties (?) using "three charges of Johnston's No.2 Flash Powder", with a 10 minute open-shutter.
. The models were John Gibson and Bob Powell.
Flash powder had fallen out of fashion by the time I started caving in 1972, so I looked up the background:
.
More recent powders are usually atomised aluminium with potassium perchlorate as the oxidizer; however the stoichiometry calculations point to a 70:30 ratio of these materials, whereas the Johnson's No.2 instructions specify 50:50.  My assumption is that Johnson's #2 was magnesium plus pot. perchlorate, the stoichiometry of which would give 50:50.
Does anyone know if this assumption is correct?
 

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Without going into the calcs. Have you thought they may be using straight chlorate as an oxidiser? Other than that, it sounds feasible. Dark Aloominum is quite go-offy stuff.

It's also possible they used an excess of the fuel, cue to the grottiness of it.
 
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