How To Make Senko Hanabi Sparklers
Introduction
In the past, I've kiddingly told fellow pyros that, at one time or another, I've made, or at
least have tried to make, every kind of fireworks device except for snakes. That was before
I heard about Senko Hanabi, though, and realized that I didn't even know what they are.
I've made some sparklers in years past, and Senko Hanabi are a kind of Japanese sparkler in
the strict sense of the word. But, after a friend gave some of them to me last year, I
realized I'd never tried to make anything like them.
According to Shimizu in Fireworks,
the Art, Science and Technique ("FAST"), Senko Hanabi is
a traditional Japanese firework, and essays about them date back to at least 1927. One
Japanese-to-English, online dictionary spells it Senkouhanabi, and defines the word as "toy
fireworks." Hanabi means "flowers of fire," and these sparklers produce miniature versions
of them.
Senko is defined as "all ages," and perhaps refers to the fact that this firework can be
enjoyed by people of all ages. Senkou is said to refer to "incense stick" and this type of
sparkler has, indeed been made on sticks, which resemble incense.
The word "sparkler" may be a bit misleading to us in the USA, though, because of what it
brings to mind. Metal wires or wood sticks, dipped in pyrotechnic compositions, emitting
bright sparks and lots of heat when they burn. "Be careful around your sister's eyes with
that glowing metal wire," Mom would shout.
This Japanese version of the sparkler is much more delicate and subtle than what we are used
to, though and a lot more safe as well. I remember how startled I felt when I first got one
of these to work, and it began emitting amazingly complex, delicate, branching sparks,
shooting out four to eight inches. Like fire-snowflakes, I thought. I was amazed.
After I burned through a pack of them, I decided to send my Mom and Dad a bundle of these
colorful little sticks. My folks are in their 80's and live in California, so I certainly
wouldn't have been comfortable sending them any real "fireworks," but I just had to show
them these mysterious little sparklers. I was excited as I imagined them going out onto
their deck and burning a few of 'em.
"You are going to be amazed by what you see when these little things really start doing
their thing," I told them.
A Bundle of Senko Hanabi Sparklers
Dissection of a Senko Hanabi
Here's a photo of an individual Senko Hanabi.
One Senko Hanabi Sparkler
The bulging section toward the left end is what contains the sparkler composition. The comp
is contained in twisted tissue paper, which can be fairly easily untwisted to empty the
contents.
Senko Hanabi Composition Removed From Sparkler
The composition is a very dark black powder. And there is not much of it in there. I have an
electronic scale, which is precise to one-tenth of a gram. It would not register the weight
of the composition that I removed from this sparkler. It barely covered the tip of a one-eighth
teaspoon measuring spoon. Its quantity equals about as much salt as you'd get if you shook
your salt shaker a couple of times.
The rest of the sparkler, the handle, is also composed of tightly rolled up tissue paper. It
feels as though it has been stiffened with a bit of a binder or glue of some sort.
Lighting a Senko Hanabi
To get a Senko Hanabi to work, you hang the composition end of it straight down from your hand.
Make sure you are in an area with no wind, steady your hand, and then light that lower end. To
really see the effect, it's best to do this in the dark, and in a ventilated area, but without
wind, so you don't have to breathe the strong sulfur smoke.
The tip will burn up to the bundle of composition, which will begin to slowly burn, and if you
are holding it still enough, a little blob of orange, glowing, molten slag will form. This is
reportedly potassium sulfide, which contains carbon from the charcoal.
Then, all of a sudden, this molten ball will begin to emit the most amazing, delicate,
branching sparks, often looking like fire-snowflakes. When you see this for the first time
you'll be amazed.
I tried, over and over, to get a nice photograph of this phenomenon and failed miserably. This
shot might give you the slightest impression of what the effect is like. You really have to see
it in person to appreciate it.
Burning Senko Hanabi Sparkler
How to Make a Senko Hanabi Sparkler
There are several Senko Hanabi tutorials available on the Internet, and, as far as I can tell,
all the information is based on the information contained in Shimizu's FAST.
The black composition is a simple one, consisting of three basic chemicals: potassium nitrate,
sulfur, and charcoal.
These are combined in a ratio of 60% potassium nitrate, 20-30% sulfur, and 10-20% charcoal. This
is a typical black powder composition, but the quantity of the sulfur is doubled or even tripled.
Sometimes lampblack or soot is used instead of charcoal. If charcoal is used, the type of charcoal
will influence the resulting sparks. Some folks use charcoal that is made of tissue paper or paper
towel, soaked in a sugar solution, and cooked in a retort until it becomes a form of charcoal. See
my Charcoal Making Secrets article.
Shimizu also lists an alternate composition, consisting of 35% potassium nitrate, 45% realgar, and
20% charcoal or soot. Realgar is a chemical that is listed as a component of some old fireworks
formulae, but it is seldom used nowadays because it has become unavailable, and it contains arsenic,
which can be a bad thing in smoke if it is inhaled!
Note: I do have a small quantity of realgar, and I tried the above formula in Senko Hanabi. Shimizu
states that realgar will produce "larger and more beautiful sparks than with sulfur." In the minimal
experimenting I performed using it, I did not find that it performed as well as the sulfur. And,
when the composition burns, it emits a thick, yellow smoke, which I was not all that thrilled to
be around.
My technique for making these experimental Senko Hanabi was as follows:
Weigh out chemicals in individual paper cups. Grind potassium nitrate and sulfur individually in a
small coffee grinder until the chemicals are very fine. Combine and screen those chemicals with the
airfloat charcoal through a 100-mesh screen several times.
I began by using 16.5 grams of the potassium nitrate, 6.5 grams of sulfur, and 4.5 grams of airfloat
charcoal. (This is approximately a 60/25/15 proportion of the components.)
Cut a piece of tissue paper, 1/2" x 2 1/2".
With slightly dampened thumbs and index fingers, begin to roll the tissue paper up at the ends, as
if I'm rolling a cigarette. (Having come of age in the 60's and 70's, I, of course, would know
nothing about this process.)
Cutting and Rolling Piece of Tissue Paper
I now dip the end of my 1/8-teaspoon, measuring spoon in my composition and scoop out just that
little bit of comp. I tap the powder out of the spoon into the little, rolled trough that was
formed in my tissue paper.
Scooping Senko Hanabi Composition, and Loading it into Tissue Paper
Then it's just a matter of using my fingers to finish rolling the little sparkler and
really twisting it into a tight little bundle. I like to hold my homemade sparkler with a
pair of tweezers, or a hemostat, in preparation for burning it.
Homemade Senko Hanabi Ready to be Lit and Tested
Results of Experiments
When I made the first sparklers, using the composition listed above, they burned far too fast and did
not form the little ball of slag which is necessary for the resulting final sparks to let fly.
So, I started to add more charcoal, one half gram at a time, as one would do to slow down a black
powder rocket composition. This did end up retarding the burn speed, but the slag ball and the sparks
never ended up forming.
Back to the drawing board. Since the original comp was burning too rapidly, I thought I'd start with
the charcoal and sulfur components, and slowly add potassium nitrate until hopefully the desired
results were achieved.
I ground the 6.5 grams of sulfur in my small coffee mill, and screened it in with my 4.5 grams of
charcoal. I weighed out the 16.5 grams of potassium nitrate and milled it by itself in the coffee
mill.
Then I started to add the potassium nitrate to the sulfur/charcoal mix a little at a time, starting
with 4 grams and adding it in 1-gram increments. I tested the composition after each increase in the
oxidizer, and after adding 11 grams of it, the ball of slag started to form and it began emitting the
sparks I was after.
With a total of 12 grams of the potassium nitrate in the mix, the sparklers were working very well,
and when I added another gram bringing the total to 13 grams, they started to burn too quickly as in
my first experiments.
So the final working formula was:
| Component |
Parts |
Percent |
| Potassium Nitrate |
12 |
52% |
| Charcoal |
4.5 |
20% |
| Sulfur |
6.5 |
28% |
| Totals |
23 |
100% |
This final formula is in the range of proportions that Shimizu demonstrated to work.
I tried both commercial airfloat and homemade spruce/pine airfloat charcoals, and they both
worked well. The homemade charcoal produced sparks which were slightly larger.
I tried the lampblack that I had on hand in the formula, instead of charcoal, but I could not
get it to work and produce sparks.
If I were going to make "production models" of these babies, I'd glue the tissue paper bundles
to a bamboo skewer, or toothpick, handle.
Dr. Shimizu goes into much greater detail concerning the chemistry dynamics of the Senko Hanabi
process, and other optional formulae, ingredients, and manufacturing processes.
When I first got into fireworking, one question was paramount in my mind: "How the heck do
they do that?" I've continued to ask that about almost every pyrotechnic device I've seen, and
I'm glad that Dr. Shimizu and others have left pointers along the way so that I could learn
more about how these things are made.
Until next time, Enjoy!
Ned
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