Confessions of a Fireworks Man

Making Rocket Nozzle Mix

This article was provided by Ned Gorski.

If you look in the end of most black powder rockets, or at the end of a gerb (fountain), you'll see a clay nozzle recessed into the end of the paper tube.

A Clay Nozzle In Paper Rocket Tube

A nozzle is a mechanical device with a hole in it, which controls and directs the flow of a liquid or gas as it passes through it. Think of the nozzle you put on the end of your garden hose. It controls the water flow, builds up higher pressure in the hose than would normally be there, and projects the water out in a nice stream. A rocket nozzle does essentially the same thing with the combustion gasses from the rocket motor. This is what propels the rocket skyward.

Typically, the nozzle in a rocket, and the solid plug at the top of the rocket motor's fuel grain, is a rammed (hand pounded with a mallet) or pressed (with a hydraulic or mechanical rocket press) mixture of wax, clay, and grog. Some folks use only clay in their rocket nozzles.

I did that for a while, but found that the clay nozzles were very susceptible to shrinkage/expansion, depending on the day's humidity. One time I pressed a bunch of wheel drivers with only bentonite clay nozzles, here in the Midwest hub of humidity. Then, when I got out to Gillette, Wyoming, which was so dry my lips started cracking, my nozzles got so loose in the rocket tubes that I could turn them with my finger. (I quickly added a ring of Elmer's glue where the clay nozzle met the tube to secure them.)

Some folks expect their rocket nozzle apertures (hole) to close a bit with the clay's expansion. So, right before flight, they open the hole up to the correct diameter with a hand-twisted drill bit. Adding wax makes the clay much less prone to this problem. Also, the clay alone, when pressed, forms a smooth, glossy surface; and nozzles and plugs have been known to get blown out of the tube by the pressure of the fuel burning. The grog in this rocket nozzle mix really helps the nozzle 'bite' into the side of the rocket tube and resist blowout.

The grog also helps the rocket nozzle resist erosion of the hole during motor burn, whereas without the grog, the clay can wear away some and the nozzle aperture (hole) opens up some during the motor burn, which reduces pressure and thrust.

The technique I use to formulate these ingredients and mix them together is similar to the one David Sleeter recommends in his Amateur Rocket Motor Construction book.

I get the wax that I like to use from the canning supplies department of my grocery store. It reads "Household Paraffin Wax, for canning, candlemaking, and many other uses." (I'm not sure why they don't list rocket nozzles on the box as one of those uses.)

Paraffin Wax for Making Rocket Nozzles

I either use bentonite clay from Skylighter or Hawthorne Bond Fireclay. They are both very fine, powdered, dry clay. (When I first started making rockets, I imagined that 'clay' should be like putty, or that I had to turn the dry clay powder into a 'play-dough' by adding water. We live and learn. No water is ever added to the clay.)

Grog is a man-made, sand-like product. It is made from fired pottery that's been crushed and screened. One well known rocket maker uses crushed red-clay flower pots. Another uses busted up and screened ceramic floor tile. I get my fine-medium grog from my local pottery supply house. Skylighter sells grog which has fine, medium and coarse (up to the size of peas) particles in it. To use Skylighter's grog, I screen out the coarse grit to end up with something that looks like fine-medium sand. A fine-meshed kitchen screen colander works well for that.

For a batch of rocket nozzle mix, I weigh out:

- One of the 4 ounce paraffin wax blocks from the box
- 30.5 ounces of the clay
- 15.5 ounces of the grog

Weigh Your Clay and Grog

Now, I add the clay and grog to a new, clean, one-gallon paint can that I get at Home Depot. After installing the lid, I shake the can to mix the two powders. Then, I open the can, make an indentation in the center of the dry mix, and lay the block of wax in the indentation.

Place Block of Paraffin Wax in the Can with Clay/Grog Mix

I then lay the lid on the top of the can loosely. (Caution, do not put the lid on tight. Pressure can build up during the heating and either burst the can or pop the lid off, sending wax and clay everywhere, and possibly causing injury.) The paint can, with the loose lid, is then put in my oven, set at 250 degrees, and cooked for about 1-2 hours or until the paraffin wax is completely melted into the dry clay/grog mix.

Heat Can at 250 ^o for 1-2 Hours

I don't use my kitchen oven lightly for this project. In fact this is the only time I do use my oven in my pyro pursuits-for cooking rocket nozzle mix. I absolutely never use it to dry or heat any pyrotechnic compositions. Never. And I keep the heat in this process down at 250 degrees to prevent the wax from igniting. Please, be mindful and careful.

Once the paraffin wax has completely melted into the dry mix, you'll see that it has only dampened about half of the clay/grog. The other half is still dry. This is remedied by removing the can from the oven with oven mitts (believe me the whole rig is hot) removing the loose lid, and stirring all the ingredients with a paint stirring stick until the wax is well incorporated into the dry mix. During this stirring, I only grabbed the can without an oven mitt once.

Mix Melted Wax with Clay/Grog Thoroughly

After stirring the nozzle mix with the stick, I install the lid, tightly this time, and, holding the can with oven mitts, shake the can violently to really incorporate the wax into the mix. Then, while the mix is still warm, I open the can and screen the mix through an old, wire mesh, kitchen colander onto kraft paper and let it cool down completely.

Screen Mix to Remove Lumps

This screening process really helps further integrate the wax into the mix, and also removes any waxy lumps which may form, which I just pitch out. The finished nozzle mix product will look like a tan, medium grained sand. I put it in an empty 5 lb. plastic chemical tub marked 'nozzle mix.'

I have another tub marked 'bulkhead mix.' This mix is the same as the nozzle mix, but with the grog portion simply replaced with more clay. I use this bulkhead mix in many driver and rocket motors, where I'm not concerned about needing the grog in the bulkhead (top clay plug) to prevent blowout. The advantage to this mix is that I can easily hand-twist a drill bit to create a passfire hole in the plug. Mix with grog in it, is very difficult to twist the bit through, and the bit would get very dull quickly.

So, let's pound a nozzle up, remove it from the paper tube, and see just what sort of component this new nozzle mix will produce. Whaddaya say?

Using a Skylighter, one-pound, 1/4" wall rocket tube (TU1068), some one-pound rocket tooling (TL1211), a rawhide mallet (I swear by this mallet), and a 6 x 6 x 4 ft. tall 'pounding post,' I'll pound a nozzle into the rocket tube, using a heaping 1/2 tablespoon measuring spoon and a funnel.

You might notice that black rubber O-Ring (from Home Depot) I like to use around my rocket tooling 'drifts.' Between Skylighter, Home Depot, and the kitchenwares department of my local department store, I get enough stuff to stay busy forever. The O-rings really help keep dust down. But, thanks to the wax, my nozzle mix is not very dusty to begin with.

One nice tip, which I got from Tom D, is to soak the rocket tubes in Minwax Wood Hardener and let them dry. This will strengthen the tubes and make them more fire-resistant. I'll dip the tubes into a can of the hardener, let them set there for a minute, remove them, and stand them on end on some plywood scrap to dry.

Rocket Tooling - Note Black O-Rings

Ram Mix into Rocket Tube with Nozzle Forming Tool and Mallet

8-12 nice whacks with the rawhide mallet and the rocket nozzle mix is well consolidated. Now, to dissect this nozzle a bit, I use a coping saw to cut the paper rocket tube off right above the nozzle, and slice the tube on both sides of the clay. You can see how the nozzle mix has consolidated into a solid mass, bulging the inside of the tube out just a bit in the process, which really locks the nozzle into the tube.

Cross Section of Cardboard Tube Showing Nozzle

Nozzle Removed from Tube

If you tap a metal spoon against the side of the clay nozzle, it 'tinks' like a little piece of solid ceramic. Nice.

In the future, we'll have an article on how to build a one-pound, black powder, charcoal-tailed rocket based on the foundation that has been laid in this article. One really nice thing about these rockets is that they provide great pyro and immediate-gratification, even in the winter months. Make up some nozzle mix, blend together some fuel, pound a motor together, attach it to a stick, and take 'er outside to fly. Smell the Smoke.

Have fun and Stay Green,

Ned Gorski

How to Make Yellow Glitter Firework Stars

Click Picture to Enlarge

Photo Courtesy of Tom Handel

Glitter is That Silvery Twinkly Part at the Bottom of These Brocade Firework Shells

This is a gold brocade firework shell. Glitter firework stars are hard to depict in slow-shutter-speed fireworks photographs, but you can get an idea of how silver glitter firework stars might look like in the sky if you enlarge the photo above (with a click).

Here's a good formula for making yellow glitter firework stars from Bob Winokur. Bob wrote the greatest treatise on making glitter firework stars and comets, Pyrotechnica 2. It's probably the most complete study of glitter firework stars ever done. This article ran in the August 1992 issue of the First Fire, the Florida Pyrotechnic Arts Guild's exceptional newsletter. Thanks to FPAG for letting us use this, and Chris Miller, for writing it.


Yellow Glitter Firework Stars
by Chris Miller-WPA

I originally got this formula from Dr. Winokur a few years ago as a universal (good for all occasions), "state of the art" yellow glitter. It has a long delay and can be used in any size firework star, from 1/4" t o 3." Firework stars 5/8" and smaller tend towards the "glitter cloud" effect and are great in shells by themselves or mixed with color firework stars in a volume ratio of 3:1 or 4:1 (color : glitter). Firework stars 3/4" and larger leave long, beautiful tails and are particularly suitable as either regular comets or crossettes.

Assuming the ingredients are lump-free, sieve the mix three times through a 20-mesh screen (window screen works fine) and bind with 8% water. This isn't a lot of water so you should knead it for several minutes to insure that the water is well incorporated. Because of the antimony sulfide, I wear a respirator when mixing the dry ingredients and latex gloves when adding the water (I'm told antimony poisoning is akin to lead or barium poisoning-very unpleasant and I don't want to find this out first hand!)

Priming is not required for these stars although some people like to prime the stars when going for the cloud effect. It is also a good idea to lightly prime the exposed face of crossettes made with this glitter formula because there is a lot less exposed ignition area on a crossette compared to a regular firework comet of the same size. Priming is cheap insurance against one or two of the stars being blown blind and diminishing the symmetry of the break (not to mention wasting all that labor that goes into making each crossette that didn't work).

YELLOW GLITTER FORMULA
Chemical	Parts by Weight
Potassium Nitrate	48
Airfloat Charcoal	9
Sulfur	11
Aluminum (12-20 micron, atomized)	9
Antimony Trisulfide, Chinese Needle	10
Sodium Bicarbonate or Sodium Oxalate	9
Dextrin	4

Winter storm wallops Chinese & US fireworks making

February 1, 2008

How today’s weather in China could impact your July 4th fireworks

If you are making fireworks yourself or are a consumer of Chinese fireworks, what is happening in China right now, today, will be affecting you.

The man who makes many of Skylighter’s Chinese fireworks products possible is Matt Palaszynski. Matt has a company in Liuyang. Liuyang is basically the center of the fireworks universe. He splits his time between there and his home in the US.

Matt works with each factory making consumer fireworks for us. He also helps us find all sorts of wonderful things we need in making fireworks. Things like screens, comet and star pumps, ematch blanks, the wonderful array of colored effect fuses we carry, and many other items that we now consider essential to fireworks making.

Matt sent me the following note yesterday. It affects all of us who are concerned about buying and making fireworks for July 4th and other events. This year, the fireworks industry worldwide is experiencing the most significant cost increases in a decade. Matt’s note explains graphically why some of these increases are happening, even as I write this.

Matt’s letter:

Hello,

I would like to update you on the weather situation in China as well as the impact on your order.

Central China is experiencing the worst winter storm in 30 years. For the last two weeks the weather has been poor and has been causing disruption to production. However, several days ago much of central and southern China was hit with an exceptional winter storm which has knocked out major power grids and shut down most transportation arteries. The forecast is for the weather to remain poor for at least the next week.

At this point, all production and transportation has ceased until at least mid-February. For those of you that were expecting shipments before Chinese New Year for arrival in March, the weather will delay your shipments.

For everyone else, production was progressing in January and shipments planned for late February and March are not likely to be significantly impacted. However, expect a delay of a few weeks vs. where we would have been without the poor weather. We were prepared for a difficult spring due to the Olympics and therefore, our production is ahead of schedule vs. typical years.

The storm is of natural disaster portions and will likely have some direct impact on the Fireworks Industry in the form of further RMB/USD appreciation. The poor weather is crippling food and fuel movement at a time of the highest annual consumption due to the holiday.

Because of this, food and fuel prices are climbing and the government is responding by allowing further appreciation of the RMB [the Chinese currency] in an effort to combat domestic price inflation. This means the RMB is likely to continue to appreciate further, further increasing the cost of importing fireworks into the USA (source China Daily Business Section, Feb 1st, 2008). Currently the RMB is at 7.19 per dollar, down from 7.5 at the beginning of the production season.

I personally have been in Liuyang since January 10th and was delayed in leaving for several days due to the weather. All roads and airports were shut-down. I just managed to get to a warm Beijing hotel room only after waiting with tens of thousands of other stranded holiday travelers for a standing room only seat on a local train.

The normal 12 hour trip took 18 long hours and was truly a once in a lifetime experience that I seem to have all too often here in China. Back in Liuyang, my team is struggling with below zero temperatures and only have a few hours of electricity (and heat) each day.

Under these conditions, we have given up on making any progress at production and the team has started their own difficult journeys to visit family and begin the most important Chinese Holiday.

Chinese New Year is an unusual holiday for us in the West to understand because all of China is shut down for several weeks. Many workers in China have left behind friends and family in the rural areas of China to work in and around the cities. During Chinese New Year they make the difficult trip back home and don't return for several weeks as they enjoy the company of friends and relatives.

As China has become more prosperous, and especially this year, workers have begun to leave for home much earlier then in years past. The reason for this is the relative prosperity in China.

Factory workers no longer are living day to day and when the weather turns cold in early January, they are leaving for the warmth of their fireplace at home with family savings accumulated from two income sources, prosperous children sending money back home, etc.

What this means for you is a more difficult production environment. We have taken steps to plan your production carefully to ensure timely delivery, however please understand that the situation is becoming more difficult: lack of workers, exceptionally poor weather, the Olympics (factories will begin to produce European orders immediately following Chinese New Year in anticipation that shipping will cease during three months of the Olympics), and other factors are combining to make spring production more difficult then usual. Rest assured we have taken steps to manage these difficulties.

I will end this update on a positive note and wish everyone a prosperous and healthy Lunar New Year.

Please see attached some photos of production from this month.

All the best to you and your families,

Matt Palaszynski
Dominator Fireworks, Liuyang, China


Making Fireworks with No Heat


Consumer Fireworks Making In January

What this means to Skylighter’s fireworks makers and buyers

Matt ain’t just awhistlin’ Dixie. The front page story in the Washington Post today reports that hundreds of thousands of people are stuck in railroad stations throughout central China.

We have a number of new products coming in our next container from Matt. But between the weather and the normal two-week holiday for Chinese New Year, it looks like it’ll be arriving later than we originally planned. The wait will be worth it. There are a couple of surprises in that shipment that most of you have never seen before. Stay tuned. Holler if you have any questions. And start making those July 4th fireworks!