Weighing and Screening Pyrotechnic Chemicals

Written by Harry Gilliam

Topics: How to Make Fireworks

Weighing out specific amounts of pyrotechnic chemicals, and screening them together to form a composition, are the most basic firework making procedures. But, as with any skill required when making your own fireworks, these fundamental jobs can be done well or poorly, which will affect the final results of our efforts.

Indeed, weighing and screening are often the most time-consuming parts of making homemade fireworks. So, the faster and more efficiently you can learn to do these tasks, the more quickly you will be able to make fireworks.

Let’s say that I want to make the Silver Titanium Fountain Fuel that was one of the compositions I made gerbs with in Fireworks Tips #108. This is one of my favorite fountain formulations and it is a simple one to start off with.

Component Percent 16-Ounce Batch 450-Gram Batch
Potassium Nitrate 0.51 8.15 ounces 229.5 grams
Sulfur 0.10 1.6 ounces 45 grams
Airfloat Charcoal 0.09 1.45 ounces 40.5 grams
Spherical Titanium 0.30 4.8 ounces 135 grams

The original formula gives me the percentages of each firework chemical. Then I pick a batch size that is suited for the project I’m working on. In this case, I want to make five of the 3/4-inch ID fireworks fountains I described in that gerb article. Each fountain will use about 3 ounces of the fuel, or about 85 grams (approximately 28.4 grams in an ounce).

So, I settled on the 16-ounce/450-gram batch size. I multiplied the percentage of each component times the total batch size to determine how much of each chemical to use. For example, 0.51, the potassium nitrate percentage, times 16 ounces, equals 8.16 ounces. I always round these ounce amounts off to the nearest 0.05-ounce, so the 8.16 ounces becomes 8.15 ounces.

Similarly, if I’m going to be working in grams, 0.51 times 450 grams equals 229.5 grams. I round gram measurements to the nearest 0.5 grams, so this result does not have to be rounded.

Once I have calculated the individual amounts of each fireworks chemical in that size batch, I add them up to make sure they do indeed total up to the desired batch size, and to verify that I didn’t make some mathematical error in my calculations.

Now I have the weights of each individual chemical I’ll be using in the project. I print that page out to have it before me as I’m performing the next steps.

I have two electronic digital scales I use only for weighing chemicals used in fireworks, one for large batches of more than a few ounces, and one for small batches of only a few ounces. I got these from my favorite fireworks-supply house.

Skylighter Digital Scales for Weighing Fireworks Compositions

Skylighter TL5020 and TL5030 Digital Scales for Weighing Fireworks Compositions

The TL5030 scale will weigh up to 15-pounds/7000-grams with a precision of 0.05-ounce/1-gram. The TL5020 pocket scale will weigh up to 222-grams/7.8-ounces with a precision of 0.1gram/0.01 ounce. Both scales can be switched back and forth between ounces and grams.

Some pyros use mechanical, triple-beam scales to weigh firework chemicals. I’ve never done that, having started out with electronic, digital scales, and stuck with them ever since. Digital scales are faster to use; they give you an instant readout. You don’t have to twiddle your thumbs waiting for that annoying beam to finally stop swinging up and down.

But, the electronic scales can go bad now and then. It is hard to tell when they have done so, since quite often they simply start to become inaccurate as they weigh stuff.

For this reason, I keep five quarters (US 25-cent pieces), which weigh exactly 1-ounce/28.5-grams, in a little plastic baggie in my shop. Before I weigh out the chemicals in a fireworks composition, I weigh my test-quarters to make sure the scale is still functioning accurately.

Testing the Accuracy of Digital Scales

Testing the Accuracy of Digital Scales, Using Five 25-Cent Pieces

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