The original formula called for 2% RIO and 6% vaseline. IMO this is too much vaseline unless you have a extremely intimate mix. The excess vaseline will help with consolidation during pressing, however it will also inhibit the RIO from working as normal. I will go out on a limb and assume the 2% RIO was added to increase its effectiveness.
From experimenting with other whistle fuels, I've noted that RG, which I used to replace the RIO, had a smoothing effect on the whistle burn, it also did not increase the burn rate. The original formula seems to be balanced at the lower limit of burn speed and optimal sound. By making the modifications I did, the fuel now burns even slower while still making a good sound.
I'm not done with the modifications yet, i plan to experiment with adding a few extra percent oxidizer and trying other phlegmatizers to up the volume.
The addition of charcoal would have a similar effect as the RG but I believe it works thru a different mechanism.
Edited by NeighborJ, 30 May 2018 - 06:21 PM.