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?
. 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?