Soluble glutinous rice starch

From PyroGuide

Description: Soluble glutinous rice starch more commonly referred to as 'SGRS' is a binder used by the Japanese star makers. SGRS is used as a water-soluble binder in many of Takeo Shimizu's formulas. This is not just because SGRS is more easily obtained in Japan than cornstarch derivatives like dextrin. SGRS does indeed have superior binding characteristics than dextrin, and somewhat less of it can be used than dextrin in most formulas.

Hazards: Soluble glutinous rice starch is not particularly toxic or dangerous.

Sources: Soluble glutinous rice starch can be hard to come by, but can be made at home:

"Glutinous rice is polished and soaked in cold water for a week. This is then steamed in a steam basket and pounded into a cohesive mass. The mass is stretched into a thin plate like a squashed cake, which is parched at a suitable temperature. The parched cake is ground into a fine powder. The powder is somewhat brownish, but has a large cohesion power and is perfectly gelatinized in combination with water. This is the most useful binding agent for firework stars." - Shimizu