markx Posted August 14, 2020 Author Posted August 14, 2020 (edited) I also tried the following fuse formulation (parts by mass): 4 KClO44 KClO32 C Not much of an increase in agressiveness compared to the 7,2/0,8 chlorate ratio, but much more sensitive towards impact. A piece of waterproofed fuse with the 50/50 ratio readily explodes when struck with an hammer....it still needs a rather premeditated attempt to get it going, but it is possible to ignite by striking with intent. The pure KClO4/C based formulations are impossible to ignite by a hammer strike. One goes tired and just disintegrates the sample. I would like to move away from the chlorate related concoctions for safety reasons, so I came up with another idea to preserve the agressive burn of a waterproofed KClO4 based fuse. The coating process itself shall always quiet down the burn rates of the core as the polymer penetrates into the fuse core and saturates it with extra fuel. Adding extra oxydiser is not effective against the effect.... To prevent this retardation action of the waterproofing substance I used a 2 step coating approach: 1) The fuse is first saturated with a solvent that does not dissolve the main waterproofing substance (be it NC, diluted contact glue or some other kind of varnish). This shall effectively prevent the waterproofing substance from penetrating into the fuse core when it is applied before the solvent from step 1 has had time to evaporate. E.g. I used azeotropic ethyl alcohol for the purpose of first saturating the core and a xylene diluted contact glue for the waterproofing. These two do not interdissolve so a barrier is created around the active fuse core. As an added feature the alcohol (or other solvent) can be colored by many dies to also mark the fuse according to core formulation or for aesthetic purposes. The die shall color the fuse very evenly if it is applied by just solvent and not a thickened waterproofing mixture. 2) The solvent soaked/colored fuse is coated with a suitable waterproofing mixture as a second step before the solvent has had time to evaporate. I used a xylene+contact glue solution for this purpose. Contact glues shall yield a very robust, flexible and totally waterproof fuse. The first coat is let dry sufficiently and if needed, another layer or layers of waterproofing is applied. Then a final drying for 24h to enable all of the solvent escape from the fuse core. This shall yield a fuse that has a waterproof coat, which does not extend past the outer surface of the treads and does not retard or alter the burn rate of the core composition. Applying the 2 step coating approach to the 80/20 KP/C formulation yields strong results when compared to the same formulation that has received the classic 1 step coating that partly or completely allows the core of the fuse to absorb the waterproofer. Perhaps even a bit too strong of a burn for practical purposes, as it seemed to somewhat surpass even the chlorate doped samples in agressiveness The negative part is that a core which is undisturbed by the inflow of binding agent/waterproofer is very suceptible to degradation by water. If the cross cut end of the fuse is dipped into water, it no longer lights. With a polymer saturated core it can take several minutes of direct water contact before the exposed end of fuse no longer lights reliably. Working in damp conditions these effects can make a huge difference in reliability, so I'm kind of leaning towards the classic 1 step coating if an overall foolproof fuse is desired. Creating a suitable fuse for "flying fish" or similar type of effects might favor the more complex 2 step coating. Just to get the most agressive burn out of it, but at the expense of reliability against moisture ingress from open cut ends of the fuse.... Edited August 14, 2020 by markx
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