Well, it’s time for my first guide here on the forum. Actually I wrote this guide back in December 2012 on a Norwegian pyroforum, but since I couldn’t find any guides for crossettes here I will give it a try here as well. As you may have understood already English is not my native language, let’s hope what I’m writing is understandable enough.
For those of you who haven’t seen the effect of a crossette yet, this is what I’m talking about. Amazing, isn’t it? I have to say that it’s not my shell:
A crossette star is usually a large pumped star. It differs from normal stars in that it has a “X” shaped cavity in one end that penetrates rather deeply, which is filled with a powerful burst charge, usually but not exclusively flash powder. The end with the cavity is capped, usually with a thick card disc glued in place, and that end, along with the sides are pasted with a layer of paper to ensure that the crossette burns only from the other end, ensuring that the effect works as intended. An alternative method involves dipping the crossette, with end disk glued on into molten wax to fireproof it.
But let’s get going, we start with the most important.
Equipment and chemicals needed:
· Hot glue gun w/glue
· Craft paper and glue, I get good results with gummed paper tape
· Crossette pump
· Black match or Chinese paper fuse ( not necessary)
· Wooden mallet, don’t use metals you will eventually destroy your pump
· Granulated black powder
· Star composition
· Graphite powder (optional)
· Burst charge
Image of equipment and crossette pump, the right image is from Skylighter.
Start by making your desired star composition, when making this guide I used 100g Tiger Tail with 7g atomized aluminium added. The Tiger tail composition is maybe the one that every pyro knows by heart, but I still choose to write it down.
Charcoal (airfloat, preferably pine)……….........44g
This formula originates from the famous Japanese pyrotechnist Takeo Shimizu, SGRS (Soluable Glutinous Rice Starch) were undoubtedly used in the original recipe since this is the most widely used binder in Japanese pyrotechnics.
Streamers are very good looking and widely used in crossettes. The crossettes are roughly treated when the break charge does its work and nothing is more sad than pulverized stars. You may therefore slightly increase the amount of binder.
As you can see from the pictures above the crossette tool is filled with the star compostion, you can choose between filling increments by eye, just push the tool into the box with the composition. Or you can choose the more dedicated and time consuming method, pre weighting amount for each crossette to get a far more superior symmetry.
Put the end of the pump against a flat suface, and hit the rammer a few times with the wooden mallet.
The following can be a bit difficult, namely to release the crossette from the pump. I would highly suggest to add a few percent of graphite powder to the composition to decrease the friction. About 2% is a good amount to start with.
When you are finished pumping all your crossettes they need to be dried, stars with high charcoal content is known to dry very slow. Do not try to dry them in the sun, this might sound logic , but they are prone to the driven in phenomenon. My crossettepump makes crossettes with a diameter of 18mm, this resulted in a total of 18 crossettes with 107 grams of compostion.
When they are fully dried you have to make the break charge, this part deals with a lot of tweaking. The first time I made them I used 50/50 potassium perchlorate/400# Magnalium flash, they do need a very strong break charge especially for such small cavities that this size offer, but it obviously was a bit to strong as you can see here:
However if the break charge is to weak a phenomenon called jetting can arise, this will make the crossette propel through the skies like a go-getter star, while this also is a very cool effect, it’s not as fun when it’s not the effect we want to obtain. But think rationally, if you are making 2 inch crossettes you have to tweak the break accordingly.
I am not going to go through the safety and mixing procedures behind making flash powder, I expect you are familiar with that before attempting to do so.
You are now ready to fill the cavity with your desired break charge, but before you do so please look at the picture of the crossette pump in the beginning of the guide. Hopefully you can see that little pin in the end of the tool, when we made the crossettes earlier this little pin made a little hole inside the bigger X shaped cavity. This hole should be filled with granulated black powder, you can use a short piece of blackmatch or Chinese paper fuse instead, but black powder might be the easiest. This is also to prevent jetting which we talked about earlier.
As you know for sure flash powder emits a huge amount of light. In some cases this can make the effect barely visible, a good advice is to add a fairly little amount of black powder to the breaking charge to subdue the strong light. This will also aid in making the charge a bit more “fluffy” .
You are now ready to make the cap, cut out a circle of carton with the same diameter as the crossette and glue it into place with some glue. If you are using a glue gun, make sure to unplug it before use. Fireworks and electricity simply don’t fit together.
Almost finished now, the only thing remaining is to cover the sides with some paper or melted wax. I haven’t tried wax yet, but gummed paper tape will do the job with great results. Just make sure to cover it very well so it can’t take fire from the sides.
As you probably know you don’t have to prime tiger tail stars, but since the surface tends to be very smooth I would suggest to just prime it with a small amount of granulated black powder to make a rougher surface. If you use other formulas you have to prime accordingly.
Just one thing to say now, hope you’ve learned something :-)