Chrysanthemum 6 & 8 Black Powder Stars
With thanks to the fine folks who put together Best of AFN II
This is an examination of the fundamental black powder compositions known as Chrysanthemum 6 & 8. A brief discussion of these compositions can be found in the Shimizu section of Fireworks Principles and Practice, by Lancaster. The formulas are reproduced below. These formulas can be seen to be essentially black powder formulas which produce a charcoal stream when made into stars because of the excess charcoal in the formulas.
- Potassium Nitrate – 58
- Charcoal, airfloat – 35
- Sulfur – 7
- Dextrin – 5
- Potassium Nitrate – 52
- Charcoal, airfloat – 42
- Sulfur – 6
- Dextrin – 5
Many Uses for These Fine Comps
These compositions have several useful properties. They are cheap to make and when used as a priming layer for round stars will allow the star to remain ignited at the very high ejection speeds which are usually encountered in the first fractions of a second after a round shell burst.
With the single exception of glittering stars, all my round stars have a surface coating of Chr. 6 of at least 1 mm thick to serve as a prime. Chr. 8 has a slightly lower ignitability and burning speed than Chr. 6 and will give a longer, thinner charcoal tail.
15-20% Ferrotitanium alloy 100 mesh can be added to Chr. 6 to produce a brighter blond colored tail which lingers in the sky longer. The ferrotitanium mix can also be used to make large palm trees.
Why and How I Tumble
Preparation of these compositions by single mixing of the ingredients will produce unsatisfactory results. The composition will burn slower and produce few sparks. The charcoal particles must be intimately coated with potassium nitrate to allow each particle to function as a burning ember when it is ejected from the burning star.
I achieve the necessary intimacy of mixing by using a ball mil which is nothing more than a rock tumbler with some .50 caliber lead balls thrown in. A 12 lb. tumbler is capable of handling a 2 lb. batch of composition at one time. A 24 hour tumbling period is usually sufficient.
These compositions are probably safer to tumble than black powder but I strongly recommend that the tumbler barrel and the composition be clean and free of any metal particles, chlorates or perchlorates to reduce the possibility of an explosion. The tumbler should be outdoors.
Important Tumbling Tips
The tumbled compositions have good burning properties but I find them unsatisfactory for immediate using in making round stars.
The extremely fine tumbler product will accrete to the surface of a wet round star but only small increments can be added in each successive layering operation during round star formation. The finished round star will take an extremely long time to dry out because of the hard compacted layers.
These difficulties can be avoided by wetting the composition with 15-20% water after it comes out of the tumblers. Then I granulate by pushing through a 12 mesh screen. I dry the granulated mix in a shallow pan for 2 days. Then the mix is put back in the tumbler and turned for just a few hours to give a product that has correct particle size distribution. The dampening also increased the intimacy of mixing by allowing the partially solubilized potassium nitrate to deposit micro crystals on the charcoal particles during the drying process.
Lacking a tumbler, a reasonable substitute for these compositions can be found by substituting commercial meal powder for the potassium nitrate. The compositions given below need not be dampened but the spark density of the tail will be somewhat reduced. See the formulations at the end of the page.
The common use of these compositions in round shells is to produce a transition from a charcoal tail to a colored core. Layering these compositions on colored cores, especially blue and purple ones, can lead to deterioration of the purity of the color. This is caused by the highly soluble potassium nitrate in the outer layer diffusing into the color core.
The only way to control this problem is to dry the stars out quickly in the sun or applying the first few increments of Chr. 6 or 8 with a 2% solution of nitrocellulose in acetone in a spray bottle as a binder. After the coated core has dried for a couple of hours, the rest of the composition can be applied with the usual water/alcohol solvent spray. The color cores will be protected from aqueous diffusion.
Applying Chr. 6 or 8 directly to a perchlorate/aluminum flitter core will not work as the mix is too cool burning to affect ignition of the high temperature ignition core. It will be necessary to use an intermediate layer of igniter composition. I usually use a mixture of Chr. 6 and perchlorate/aluminum as an intermediate layer.
Commercial Meal D Substitutions
- Meal D – 77
- Charcoal – 23
- Dextrin – 5
- Meal D – 69
- Charcoal – 31
- Dextrin – 5