Tutorial: Crossettes

[mathiasxx94]

Tutorial: Crossettes

 

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:

 

http://www.youtube.com/watch?v=dvxUVg0e8gQ

 

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

· Carton

· Craft paper and glue, I get good results with gummed paper tape

· Compass

· Scissor

· 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

 

 

http://s9.postimage.org/dbz4s1juz/image.jpg http://s9.postimage.org/esana6mrv/image.jpg

Image of equipment and crossette pump, the right image is from Skylighter.

 

Procedure:

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.

Potassium nitrate………………………………….44g

Charcoal (airfloat, preferably pine)……….........44g

Sulfur…………………………………………………6g

Dextrin/SGRS………………………………………..6g

 

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.

 

http://s7.postimage.org/hs7inaxh3/image.jpg http://s7.postimage.org/hthggpzav/image.jpg

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.

 

http://s13.postimage.org/cll7b353n/image.jpg http://s13.postimage.org/6lxg7fkb7/image.jpg

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.

 

http://s9.postimage.org/4r69k8qmj/image.jpg

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.

 

http://s7.postimage.org/7wtwra41j/image.jpg http://s7.postimage.org/6vto25n1z/image.jpg

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:

http://www.youtube.com/watch?v=CtlGF1pez_8

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.

 

http://s1.postimage.org/c676428bf/image.jpg

 

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.

 

http://s13.postimage.org/ob7ki0plf/image.jpg

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.

 

http://s13.postimage.org/65z7hpfgz/image.jpg

 

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 :-)

[Bobosan]

Looks like tedious work with smaller crossettes. Nice tut...thank you.

[mathiasxx94]

Thank you! Yes it is a bit tedious especially when making a lot of them, but I like that I can make small ball shells with crossettes.

[Zumber]

overall tutorial was nice..

Any special reason for adding 7g of atomized(what mesh?) aluminium in TT composition?

[mathiasxx94]

The aluminium (250# atomized) was an attempt on spicing up the formula, it did not really show up in the video here, don't know why. But I made some stars for NYE with this formula and the effect was pretty cool, sort of delayed silver flashes in the tail.

[AlexPyro66]

Great tutorial and I was ready to buy a crossette pump very helpful

[vegasdude]

Thanks for the Tutorial. Now I got to order a crossette pump... Edited January 23, 2013 by vegasdude

[Mumbles]

Please do note that crossette pumps made by the common US toolmakers will have a much smaller cavity. They're the original design that those chinese brass pumps are based from initially. They're more likely to jet, but also much harder to overbreak. They may also come in round hole instead of fluted or cruciform cavity.

 

By the way, filling in the bottom of the cavity with a fine grained powder is called "tacking" the crossette. After you add it, lightly consolidating the grains will lock them into place, while maintaining fire paths. I'd recommend something fairly fine like 7FA or 4Fg (same size) which is -40+100 mesh. I normally just use the dust remaining after granulating and grading.

[Zingy]

Many of us old timers, started off using the crossette pumps made with the cylinder cavity, for a 'shot'. The 'shot' was basically a short, fat, hand made, fire cracker, with a short black match fuse. The 'shot' prevented the jetting, and also gave a larger spread, for the break of each crossette comet. However, the four sided fluted cavity pumps gave an awesomely admired, four sided symmetrical break, for each crossette comet, converting many of us, doing pyro for decades. Edited January 23, 2013 by Zingy

[AlexPyro66]

I will try to make a 1'' crossete pump with the four sided cavity.Is it a problem if the cavity is out of wood?

[AirCowPeacock]

I think you will have trouble with it sticking. If you do, make it smooth and sealed.

[mathiasxx94]

Alex: I actually tried to make one out of wood before I bought the pump, but I found it pretty hard to work with. The comp was always sticking to the tool, however some lacquer might solve that. But you also got the problem with symmetry of the cavity former, I used a handheld Dremel to make it and the result was not very good. If you got the right tools it might work, but I would suggest to buy one, they are not that expensive.

 

BTW: Thanks for the additional info Mumbles, and Zingy

 

I would like to get an extra cylinder "tip" for the pump to change between crossettes and cavity stars.

[Mumbles]

There are people who make such a tool if you're ever interested. They come with tips to make crossettes, cavity comets, and flat comets. I've been thinking about getting one to do both round and fluted crossettes, as well as cavity comets, and flat comets.

[AlexPyro66]

Alex: I actually tried to make one out of wood before I bought the pump, but I found it pretty hard to work with. The comp was always sticking to the tool, however some lacquer might solve that. But you also got the problem with symmetry of the cavity former, I used a handheld Dremel to make it and the result was not very good. If you got the right tools it might work, but I would suggest to buy one, they are not that expensive.

 

BTW: Thanks for the additional info Mumbles, and Zingy

 

I would like to get an extra cylinder "tip" for the pump to change between crossettes and cavity stars.

Yes wooden propably be good for crossettes.I know that crossete pumps are cheap but here in greece if you want to buy any kind of pyro tools you will have to pay at least 45$ for the shipping so they are a litle pricie.Ok another idea i have an aluminium foundry can i make a wooden prototype and cast it? Edited January 24, 2013 by AlexPyro66

[MrB]

Wolter Pyro Tools has these "quad pumps" for making Crossettes. Since this is the FAQ/Tutorial for Crossettes, does anyone care to elaborate on the design, and it's advantage?

 

I guess your supposed to take the 4 parts, hold em together, TIGHTLY, somehow, seal one end, add break, and seal the other end, and remove whatever held em together, leaving the sides exposed.But wouldn't this make for a crossette that is very easy to blow apart when the shell breaks, not to mention that even if it holds together, the "cracks" where the 4 parts join up will be fairly lose, the only thing holding them together being the end covers...

I just don't get it, does anyone use these and care to do a little show and tell? (I probably got something about the use of these wrong, there might be something obvious i'm missing. Wouldn't be the first time i'm proving myself not to be half as bright as i like to think i am.

B!

[Mumbles]

I will start this off by saying I really want a quad pump. Quad pumps, while able to make a crossette type of effect, is not actually designed to do so. They're used to make quadrant inserts, as shown in the following videos.

 

2 sets of 4 inserts are placed 45 degrees off set from one another and rolled up in a few turns of kraft. The center cavity is fused and filled with burst. Typically BP augmented with flash is used due to the limited space. Then you close it up, spike and paste as normal.

 

 

[californiapyro]

alex, just so you know, I can ship anywhere in the world on some items for as little as $15. I am sure other suppliers can do the same Just gotta ask

[MrB]

Ah, so while they are crossettes, they aren't self-contained, and you simply make a shell with a set, or a few offset sets. Duh, that wasn't so hard to figure out, now that you've pointed it out.

B!

 

Edit

I'm pretty sure i've even seen the effect in action, but never linked the two together. Some days, things just don't go well. But do these days have to stack next to one and other, for years on end?

/Edit

Edited January 25, 2013 by MrB

[Mumbles]

They're really not very common. I've never actually seen one in person. I've only seen that video, and read some description of them in Hardt as well as some description from Mike Swisher. That doesn't mean I don't want the tooling though. Farfalle weren't very common when a few of us started making them 6 years, and now look at them.

 

Mathias, have you done any comparisons between weighing out the composition for each comet and just trimming the length with the pin on the tooling? While it goes against reason, I've been told that trimming gives a more accurate effect.

[Algenco]

Mumbles, I want the quad pumps too, maybe we can get a group buy

[dynomike1]

I guess i am confused about something since i don't have one yet. Mahis said put the powder in and then tape it.Am i reading that right ? Looks like you would tape it then put the powder in then cap it. Then on the other hand maybe that little hole full of powder is all you need. Don't know. Edited February 3, 2013 by dynomike1

[Mumbles]

When I've made them, I always have the paper that wraps the crossettes lay down over the top. Doing this, you need to wrap them afterwards. I've never had very good luck getting enough confinement from a glued on disk alone, and found that the extra reinforcement from the pasted paper or tape over the top to give better results.

[dynomike1]

So what you are saying is, that little hole that the pump leaves holds enough powder for burst. Edited February 4, 2013 by dynomike1

[MrB]

Thats what it's for.

The closed end is what leaves the trail, the flame burns in to the cavity, and blows the whole thing apart. (That is, the closed end of the crossette, not the closed end of the cavity.) So if you want a longer trail, a slower composition, or a longer "end" on the crossette is the options.

B!

[Scott2Fisher]

I'm new to the hobby and would like to tackle the crossette. Ive made the tooling and produced some crossettes with an OD of ~1.25" and ID of ~.75" with the cruciform shape . I have figured out the whole lift charge and delay fuse mystery so im almost ready to launch these things. my problem is the burst charge. what do i do? Can i use only granulated BP? Mumbles said to augment it with flash powder. however, in my reading you have to have written a doctorate on the history and science of pyrotechnics to be allowed to ask any questions about flash powder so im looking to stay away from it until the gods deem me ready.