Asphaltum = Dragon’s Eggs
From a post by Mike Swisher on rec.pyro: The matrix composition is: 51.5 salpetre 33.0 air float charcoal, 6.5 sulphur, 3.0 aluminum flitters (US #813), and 6.0 dextrine. To 100 parts of this mixture are added at least 25 parts of granules. More may be used depending upon the density of the crackling effect desired. The resultant mixture is dampened with water for pumping.