This recipe calls for a 60/40 mix of KNO3 and white table sugar by weight, and I'm going to make a 100 gram batch, so I'm adding 60 grams of stump remover first, followed by 40 grams of granulated white sugar. I'll need some sort of container to hold this in, and I'm thinking these Mega Block Legos might work. At this point, the mixture is just runny enough that it can be coaxed into the container. It takes about 60 grams to fill this red block, and when I've cooked up a little more, I'll add that to the blue one. It's darker in color because it cooked longer, and generally speaking, I think the less it is cooked, the better. Another batch was made using a mix of 58% Stump Remover, 29% Sugar, and this time I used 13% Corn syrup, and 30mL water. The water was cooked out the same way as the last, and then about 1 gram of homemade rust powder was added, and stirred in throughly.
When it was ready, it looked like a creamy chocolate frosting, and I packed that into the green LEGO. I may have accidentally trapped an air bubble inside. Overall I think I'm happiest with these mixtures using the rust. With a different homemade casing that actually has a nozzle, I was able to get a successful rocket launch that I think went a couple thousand feet high.