When you strike a match, you do not think of all the effort, which has gone into preparing the gelatine applied to the match head as a binder.
Many different materials have to be combined to produce a safety match. Some of them prevent glowing of the wood or cardboard after burning, others promote flaming. There are chemicals in the match head composition acting as oxygen carriers or controlling the burning speed. We also find flame forming additives, colouring matter, glass powder and gelatine in the match head composition.
What is gelatine? Gelatine belongs to the chemical group of scleroproteins. It is therefore an albuminious substance, mainly produced from collagen of connective tissues found in animal skin or bones. An older term for gelatine is glue, which is usually reserved for adhesives containing basic materials of animal, vegetable or synthetic origin dissolved in water. We will use the word 'gelatine' in this article to avoid confusion and to enhance the high quality demand by today's industry.
Technical gelatine is produced from natural raw materials, which grow again, looking back on a 4,000 years old history. We can trace the first application of gelatine back to Egypt. It was found in many graves as part of fine furniture. There are also paintings describing the use of gelatine in the ancient workshops. A piece of gelatine was even found near the temple of Hatshepsut in Der-el-Bari. The art of making and using gelatine travelled from Egypt to Greece. Here it was described by the philosopher Theophrast (371 - 286 b. C.). Later the Romans took over from the conquered Greeks. Plinius described the production of gelatine and reported that the doors of a temple made by using gelatine were still as good as new after 400 years. Many recipes and reports regarding gelatine come from cloisters in medieval times. Christopher Weigel made a picture of a 'glue factory' as early as in 1694, but industrial production did not start until the turn of the last century.
Let us learn a little bit more about gelatine in general: The hide contains a 'glue-spending' substance called 'collagen'. Collagen is converted into glutin, a high-molecular substance through chemical and physical processes. After various extracting, cleaning- and drying processes gelatine is obtained in granulate or powder form. Gelatine swells, but is not soluble in cold water. After cooling down, a warm gelatine solution will grow stiff. Even at low concentrations it forms a gel. This transition from solid to gel allows very quick adherence without proper drying. In most cases sufficient initial strength is accomplished.
Gelatine is suitable for joining and impregnating materials, which allow its mechanical anchoring and the evaporation of the water. It may be re-dissolved in water, but it is resistant to most organic solvents. Gelatine will change to glutose, if it is exposed to temperatures over 65°C for a long time. As glutose shows no adhesive properties, there will be a loss of quality under these conditions.
Gelatine is best equipped for the production of matches, but there are some special requirements for this application. The gelatine should act as a binder to hold all the different ingredients together, without disturbing their functions. This must be accomplished even under very serious conditions, because at the moment of ignition, the temperature may reach values of up to 2,000°C for a short time. It is important that the head stays in one piece. After all, you do want to light a candle or cigarette and not a piece of clothing.
A porous structure containing air is desired for the head and will help to improve the ignition performance. Therefore, the gelatine solution has to provide very special foaming characteristics. Not only is the amount of foam important, but stability also plays a very important role. Only carefully produced, technical gelatine with very small amounts of impurities, especially fat free gelatine, shows this foaming behaviour, using the natural properties of proteins, which are the building blocks of gelatine.
Furthermore, parameters like: viscosity, pH-value, keeping- and gelation power play an important role. Last but not least, there should be no shrinkage of the match head during drying, as can be observed when using other types of glue.
