Dissolve 6 lb granulated sugar, 2 lb glucose, and 0.5 oz cream of tartar in 3 lb, 4 oz of water and bring to a boil. When cooled to 110'F or below, add rum extract to taste. The syrup should be hot and the cakes cool to obtain the best penetration. A 1-lb cake should absorb about 4 oz of syrup.