Fireworks.org – The World’s Fireworks Community › Forums › Pyro Technology › Any tips on getting a cleaner break on 4 inch shells? › Reply To: Any tips on getting a cleaner break on 4 inch shells?
I had the same issue with my early shells man. Took me a while to figure out it was my pasting technique all along. I was rushing the layers and getting weak spots.
Something that helped me a ton was switching to a hemp string for spiking instead of cotton. Way less stretch, tighter wrap. Also started using a break charge of 60/40 KNO3/sulfur with 5% aluminum ? gives a real crisp crack instead of a puff.
One more thing ? check your lift charge too. If you’re not getting consistent height your break position will be all over the place and the pattern will look uneven no matter what.
What mortar tube length are you using? I found 4:1 ratio (4x diameter) gives the best results for canisters.