11 replies to this topic

[pyrotechnist]

Does anyone know if KNO3 substituted with Sodium Nitrate is any good for BP? Done a few tests and it seems Sodium Nitrate produces a bit more heat and gas than my standard mix but if dampened, ground and left to dry the burn rate seems to decrease . I also seem to get a lot of white - orange dross as well as it sets rock solid. The weird thing is the powder worked fine when dry and left hardly any to no dross at all but when wet with a 50/50 alcohol and water mix seems to go crap.

The next test is to use

KNO3 65
NaNO3 10
Charcoal (Paper based) 15
Sulfur 10

[spanner]

Sodium nitrate is sometimes associated with "Blasting Powder" as used in early mining. As you've found, it's hygroscopic but if kept dry works OK as a substitute.

You wouldn't want to use BP made with sodium nitrate in color comps- the Na will cause it to be yellow.

Edited by spanner, 01 November 2008 - 02:11 AM.

[Arthur Brown]

Why? It's hygroscopic and is always damp unless you keep it dessicated. It is also strongly yellow in flame colour.

Old blasting grades of BP used to use Sodium nitrate but these were made very dry then coated with wax to keep them dry.

[pyrotechnist]

I ain't getting issues with it supping up moisture as its rock solid and pretty much really dry (keep it under an enclosed lamp emitting a small amount of heat). It is that solid without any dextrin or other binder that its grain strength is virtually comparable to commercial which I find really weird.

Back to making 200g of BP by hand (literally, motor and pestle). More tests to follow!

[spanner]

It's a good bet that it is still damp. You should think about screening it then drying it thoroughly. But even with it dry, as you mortar and pestle it into BP, it will be absorbing moisture from the air.

[Arthur Brown]

You have scales? Get a lump and dry it until the weight remains constant see what weight it loses.

[pyrotechnist]

So is this stuff only suitable for stars? yes I have scales and may try that out. I have opted to just make 300g of normal black powder.

[spanner]

These comps are from Wouter Visser's "Pratical Pyrotechnics": http://www.wfvisser....nl/indexEN.html

Rocket Propellant #7 (NaNO3 propellant)
Source: rec.pyrotechnics. Posted by Chris Beauregard <cpbeaure@descartes.waterloo.edu
Comments: The burning rate of this rocket fuels depends much less on pressure than that of black powder. This widens the accetable limits of the ratio nozzle area/fuel surface area.

Sodium nitrate....................................69
Carbon............................................27
Sulfur............................................4

Magnesium Flare #2
Source: Kirk-Otthmer technical encyclopedia[8], chapter 'Explosives and Propellants'.
Comments: Heat of reaction: 6.134 kJ/g, Gas volume: 74 cm3/g, ignition temperature: 640°C, impact sensitivity test: 19% of TNT

Sodium nitrate....................................38
Magnesium.........................................50
Laminac...........................................5

Yellow Flash
Source: "Spelen met vuur"[9]

Magnesium.........................................1
Sodium nitrate....................................6

Priming Composition #7
Source: Shimizu[1], page 218
Comments: A standard black powder priming cannot be used with stars that contain ammonium perchlorate, since a double decomposition reaction forms the highly hygroscopic ammonium nitrate. This makes the stars unignitable. Replacing the potassium nitrate prime by this priming composition solves that problem.

Sodium nitrate....................................80
Paulownia coal....................................15
Sulfur............................................5

Yellow Star #5
Source: Composition from Shimizu[1], page 215.

Potassium perchlorate.............................68
Red gum...........................................18
Lampblack.........................................2
Sodium nitrate....................................7
Soluble glutinous rice starch.....................5

And this:
Yellow Star Allen Faber
Sodium nitrate 24 pt.
Sulfur 9
Charcoal 6
Strontium sulphate 2
Sodium bicarbonate 2

[pyrotechnist]

Thanks for the formulas they will come in handy.

[megabusa]

I Used to use Sodium Nitrate in my 1" rockets.

The orange flame added to the effect of the tail & looked pretty good, but it was a nightmare to keep it dry - even in summer !

Get some bags of silica gel from packaging & store the NaNO3, comps & finished products in an airtight bag with a bag of silica gell granules inside. That used to work for me.

[Potassium chlorate]

NaNO3 is great for yellow flash. I made 1 kg(!) 85:15 NaNO3/Mg once. It was a tremendous flash but hardly any report. It just went "whoof!".

Yesterday I was going to make a little smoke bomb (80 grams) with food store grade NaNO3 and "flour sugar" (finely powdered sugar). I used the common 60:40 mix for KNO3/sugar. Guess my surprise when it went off with a bang louder than that of more then 10 times as much technical grade NaNO3 and Mg! It was obviously of very good quality and very dry. They sell it in 40 gram bags in food stores here.

Edited by Pyroswede, 08 November 2008 - 02:50 PM.

[kcnkickthecat]

A mixture of NaNO₃ and KNO₃ in a certain ratio, please don't ask me what ratio I can't remember , has a lower melting/decomposition temperature than either of the constituent oxidisers by themselves. The 'Tamman temperature' (the point halfway to the melting point, on an absolute scale) of NaNO3 is quite low anyway, ~17^oC, if my memory serves me correctly. Above this temperature the ease of accidental ignition of the composition it contains increases greatly.

Because of this, sodium/potassium nitrate BP may be quite sensitive to friction, impact and the other usual unwanted ignition suspects. Don't take this as gospel though, it's just a theory and I may be wrong.