How To Convert Pyrotechnic Formulas

Quite often, pyrotechnic formulas, especially older ones, do not have the ingredients listed as a percentage of the total pyrotechnic formula, only as parts per total weight of the mix. An example of this would be the saxon pyrotechnic formula out of the Weingart book, which is:

Meal Powder 4
Sulfur 2
Potassium Nitrate 2
Mixed Charcoal 1
Total 9

In order to compare pyrotechnic formulas from different sources, they must both be percentage-based formulas, such as this saxon pyrotechnic formula from Lancaster:

Meal Powder 50
Potassium Nitrate 30
Charcoal 40/10 Mesh 10
Sulfur 10
Total 100

Here we see the pyrotechnic formula totals 100, so that now we can express each ingredient as a percentage of the total (for instance, Potassium Nitrate makes up 30% of the total). In order to compare the Weingart pyrotechnic formula to the Lancaster pyrotechnic formula, it is necessary to convert Weingart's pyrotechnic formula so that the total adds up to 100.

Fortunately, this is easy to do. First divide 100 by the total of the pyrotechnic formula you wish to convert (in this case, 9)

100 / 9 = 11.111

Using the result of this transaction, multiply each ingredient in the pyrotechnic formula to be converted and round to the nearest whole number:

Meal Powder 4 x 11.111 = 44.444 = 45
Sulfur 2 x 11.111 = 22.222 = 22
Potassium Nitrate 2 x 11.111 = 22.222 = 22
Mixed Charcoal 1 x 11.111 = 11.111 = 11
Total 100

As is often the case since we are rounding to the nearest whole number, the total will be 99 or 101. Generally, just adjust the largest amount of material up or down 1% to get the total at 100.

We can now clearly see that the Lancaster pyrotechnic formula uses 5% more meal powder, 8% more Potassium Nitrate, 1% less sulfur and 12% less charcoal. Therefore, even before we mix an ounce of precious chemical we can make an educated guess that the Lancaster pyrotechnic formula will probably burn faster due to the increased meal and oxidizer content.

Any weight-based pyrotechnic formula can be converted to a percentage-based formula by using this technique.

You will be surprised how many of the seemingly different pyrotechnic formulas in a lot of the older books turn out to be nearly identical when converted to percentages. Making these conversions in your lab notebook can be very enlightening and should be done as a matter of habit. You are keeping a notebook, aren't you? Remember: apples to apples.

Many times pyrotechnic formulas for fountains, gerbs, and glitter stars, (among others), are given as having a certain amount of meal powder included with the rest of the chemicals. Most of these will work just fine, although normally a bit less vigorously, if the components of meal powder, potassium nitrate, charcoal and sulfur, are substituted in the pyrotechnic formula. The problem is figuring the individual amounts of each of these three to add in.

Begin by converting the pyrotechnic formula to percentages. As an example, here is a pyrotechnic formula from Weingart for a simple gerb:

Original Converted to %
Meal Powder 6 55
Potassium Nitrate 2 18
Sulfur 1 9
Charcoal 1 9
Steel filings 1 9
Total: 11 100

In this pyrotechnic formula, meal powder makes up 55% of the mix. Since meal powder is 75% Potassium Nitrate, 15% Charcoal, and 10 % Sulfur, all that is needed is to take 55% of each of those values and add them back into the pyrotechnic formula; so you have:

55% of 75 = 41.25
55% of 15 = 8.25
55% of 10 = 5.50

Rounding off to the nearest whole number we now have:

Potassium Nitrate 41
Charcoal, Meal 8
Sulfur 6
Potassium Nitrate 18
Charcoal 9
Sulfur 9
Steel Filings 9
Total 100

Combining like terms, the final pyrotechnic formula works out to be:

Potassium Nitrate 59
Charcoal 17
Sulfur 15
Steel Filings 9
Total 100

Note that the final values still add up to 100% - a good way to check your work.

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