Senko-Hanabi

With the next composition we obtain the same result. 

Place the potassium hydroxide in a porcelain crucible and heat it until it melts. Add the mixture of the sulphur and charcoal, which is previously prepared, to this. The potassium hydroxide reacts with the sulphur to produce a black substance in a plastic state. Stir well and knead it. The reaction may be as follows  

At last we obtain a black, dough-like mass, which smells of hydrogen sulphide. 

When we replace the potassium hydroxide with sodium hydroxide, we obtain strange sparks of another shape rather like many pieces of string thrown into the air  

The fire ball substances, which are obtained by suddenly cooling the fire ball at the beginning of the Senko-Hanabi display or the above methods, have a life of less than 4 5 hours. After this time the siibstances lose their ability to spark. Perhaps it may be caused by the degeneration of the potassium sulphide. 

---

It is important to study the phenomenon of the Senko-Hanabi in order to acquire knowledge about the phenomena of the fire dust and sparks, and further about the prevention of accidents. 

Senko-Hanabi is an old firework in Japan. In 1927 Dr.Nakaya first presented the results of his physical study on this itemCNakaya and Sekiguchi Riken Report,6,p.IO83(1927)). In 1957 the author made an effort to clarify the mechanism of sparks from the chemical point of view[T. Shimizu Studies in fireworks on the Japanese Senko-Hanabi, Journal of the Industrial Explosive Society,Japan,1, p.359(1957 )) A.Maeda and his pupils at Shinjuku High School in Tokyo made experiments on the problem in detail(Shinjuku-Koko(High School), Studies on the old Japanese firework Senko-Hanabi(1962)). Here is a summary of the important results in precis. 

The phenomenon of Senko-hanabi occurs after a black powder-type composition burns out at the cinder stage it coheres into a fire ball and emits many pine needle-like sparks from its surface as it reacts with oxygen in the air. In this case the remaining charcoal and potassium... 

The pine needle-like sparks resemble the sparks of iron which are obtained by grinding iron. In the latter case, the melted substance is iron and the sparks are caused by the explosion of the carbon in the iron. Accordingly we can get some idea of the carbon content of the iron by observing the sparks[Kawai Metal materials,p.91(I960)1. At 0,2% carbon content there are few sparks, but as the carbon increases more sparks are produced, and at 0.7 0.8% carbon content we get most sparks. The difference betv een Senko-Hanabi and iron sparks lies in the fact that in the former the carbon is not in a dissolved state, but in the latter it is dissolved. 

Fig. f9 Effective zones of Senko-Hanabi composition of KNOj-S-C system... 

There has been a problem with the kind of carbon powder from the earliest times. Pine soot generally gives the largest pine needle-like sparks but sometimes we have a kind of soot which gives only small sparks. The reason is not clear at present. I.Yamamoto, one of manufacturers of Senko-Hanabi, said that the sparks appear with considerable difference depending on the place where the soot condenses during production. 

There are two ways to hold the composition of Senko-Hanabi one is a dry process twisting a piece of Japanese paper tape 23 mm wide and 200 mm long containing about 0.09 of the composition at one end the other is a wet process where sticks made of rush or straw are dipped into a liquid mixture to a desired depth, withdrawn and dried in the sun. The liquid mixture is made by adding glutinous rice starch and water to the composition. 

According to Maeda s classification, the life of a Senko-Hanabi is divided into five periods as follows (1) Birth (11 to 15 seconds). Hold a piece keeping the composition end down and ignite it at the end. It burns violently, leaving a wire-like cinder. (2) Infancy(3 to seconds). The cinder shrinks gradually to a fire ball, which increases in brilliancy. In the fire ball, substances move like boiling water. The temperature of the ball is about 86o C. (3) Youth(8 to 11 seconds). Large intensive pine needle-like spaiks are projected from the fire ball. ( ) Middle age(9 to 10 seconds). From the fire ball somewhat small sparks are very frequently projected. The temperature becomes 9 0°C. (5) Old age(l8 to 20 seconds). 

Various relationships with the phenomenon of Senko-Hanabi... 

On the good side, we can mention the production of fire dust or pine needle-like sparks. The Senko-Hanabi is the most popular one. The "Silver Wave"(see 15 2) also belong to this type. In this case the realgar content considerably helps the Senko-Hanabi phenomenon. The sparks looks like red, green and yellow twinkling stars. 

The compositions by R.Lancaster(P.Lancaster Fireworks, principles and practice,p.89(1972)) contain gunpowder(black powder), sulphur, potassium nitrate, charcoal etc., and the twinkling or glittering effect might be caused by the Senko-Hanabi reaction of the cinder. 

On the bad side here is an example. When the gas, v/hich is produced by the burning of black powder, streams out of a narrow orifice, it accumulates the potassium sulphide particles it contains, at the outlet in drops. This causes the Senko-Hanabi phenomenon. 

The sparks look like pine needles as in the case of Senko-Hanabi. They are produced by branching explosively from one particle, one after another. 

The particles are so fine that it spreads well into a mixture, even if the amount is small. This characteristic is a great advantage as an ignition agent. As a component of the Senko-Hanabi composition, it creates a big spark with many branches, and has been used for this from old times. The high price is the major defect. 

Carbon black used for industry is different from the lamp black. It is made from natural gas, acetylene gas, anthracene or coal tar. This material has a high specific gravity(1.8 2.1 g/cc) and contains carbon with a graphite structure the crystalline nature can be observed by X ray techniques It is rather difficult to burn it in the air and it did not produce sparks in Senko-Hanabi, when it was tested by the author. 

The process for manufacturing matches, quick-match, Senko-Hanabi, sparklers or searchlights, which utilize relatively insensitive compositions dipping them on to sticks, string or pieces of paper, may be described as a wet process, but the purpose lies not so much in safe mixing, but rather in the manner in which the composition is held, and in this case the wet process is not always necessary for the mixing of the component materials. 

Twisting involves twisting a piece of paper tape with a composition in the core. This is applied, e.g., to a kind of Japanese sparkler Senko-Hanabi or some fuses. Loading involves filling a container with a composition lightly, e.g., in the case of reports in which the composition is filled with an apparent specific gravity of about 0.6 to allow it to explode perfectly, or in the case of lances, where the composition is consolidated rather better to avoid explosion. No water or solvent is added to the composition, and there is no need for drying, but they are... 

When a metal powder is contained in a black powder type composition, it creates fire dust or sparks of special beautiful effect. It may come from the "Senko Hanabi effect. 

The point has been made that mortars must be swept after each shot in ordinary shooting, and after each series of shots in quick shooting with a stick attached by a piece of cloth inside the wall. This is to remove the cinder from the lifting charge and to allow the shell to be loaded easily. It is also important to remove the remaining fire which occurs due to the Senko-Hanabi phenomenon in the cinder. After the display is finished wash the mortars with water, especially the inside, and dry them well. When they are completely dry they are biledl The cinder from... 

The phenomenon of Senko-Hanabi(Japanese sparklers) 68 10.5 Various relationship with the phenomenon of... 

The fire dust or sparks which are produced by iron or carbon create the colour which resembles that of the black body. The colour of the sparks of "Senko-Hanabi" which is caused not only by carbon but also other materials, also resembles the colour of the black body. We feel that the colour of the aluminium fire dust is a little different from the black body. The colour changes from red-orange to yellow, white yellow and silver as the temperature increases, and the locus may be written as the LH line (Fig.33). Anyhow we can produce various colours of the fire dust or sparks except blue and green by adjusting the temperature and selecting substances which make up the component material in firework compositions according to the principle of the colour temperature. 

From the above study it is clear that we might make such Senko-Hanabi-like sparks with only the two materials, carbon particles and potassium sulphide. The author succeeded in this. 

Sometimes we see the sparkling of a fire ball caused by burnt quick match. When shells are fired one by one in the same mortar, sometimes an unexpected explosion occurs when a lifting charge is loaded into the mortar. This may be caused by the remaining fire in the mortar which is activated a little while by the Senko-Hanabi reaction. Accordingly, we must scrub the inside of the mortar and check it before loading to see if the fire spot remains in it or not. 

---