Dextrin
From PyroGuide
Formula: Mixture of polysaccharides.
Description: Dextrin is one of the most commonly used binders in pyrotechnics as it is very cheap and readily available. It is water-soluble and can produce rock hard stars. Its cohesive power is weaker than that of SGRS anyway. Dextrin should not be used in a very damp climate as the stars tend to get wet rather than non-dextrin stars. Western pyrotechnics uses dextrin rather than SGRS, while the former is not popular in Japan and China.
Hazards: Dextrin is not particularly toxic or dangerous.
Sources: Dextrin is easily prepared from starch. Potato and cornstarch will both work fine. The starch is spread out on a sheet in a layer about 1 cm thick and placed in the oven. The oven is then heated to 220°C(400°F) for several hours. The dextrin will turn slightly yellowish brown. One way to check if all the starch has been converted is to dissolve a small sample in boiling hot water and add a drop of KI3 solution (Lugol's iodine solution). A blue colour indicates presence of starch, which means the conversion hasn't completed yet. KI3 solution is conveniently prepared by dissolving a crystal of elemental iodine in a potassium iodide solution.
