If they burn without cracking lower the oxidizer and MgAl amount. If they fail to smoulder go back one step. Lower the MgAl amount and don't change the oxidizer.
Sounds like your MgAl is more reactive than mine for some reason... So just lower the amount you use by 1/3rd and test again... Then if it works... Fine tune! If you have a working formula for a certain mesh MgAl post it. Bismuth dragon eggs are easy to fine tune once you get a feel for it. The issue is that different batches of MgAl can have different amounts of Al vs Mg, and mesh sizes may be more to a higher or lower range than labeled... Some may contain more reactive dust, and some may have been milled differently changing the reactivity. Etc... The only way to get perfect consistency is to alloy and grind the Mg and Al yourself.
The ratio of CuO to Bismuth Trioxide is unimportant in my experience. My dragon eggs work all the way from 15% bismuth to 50% and probably higher. (Only tested to there.) Best sound is with a decent amount of bismuth though. You can lower and raise the amount of bismuth and change the CuO accordingly and the composition still performs the same within a HUGE range.
Just follow these two rules and your good for tuning...
1. If it burns use less MgAl.
2. If it doesn't stay lit with a torch ignition use more MgAl.
If both of those rules fail... Change the amount of KClO4 and test over. I highly doubt those rules will fail you with bismuth and my main formula. When you shift the MgAl ratio up and down change CuO accordingly.
The KCLO4 oxidizer assists smoulder. It will prevent the crackling of dragon eggs in amounts over 7g and lead them straight to burn in my experience. Keep it in the 2-6g range. 3% is a good level to keep it at through the testing stage. It will assist smoulder and not cause any issues at that amount.
Edited by usapyro, 30 January 2012 - 01:32 AM.