The cotton balls didn't catch fire, because A) they weren't 100% cotton, and B) I'd put too much vaseline in them and I'd kept them smooshed in little zip bags.
Are you sure that this is due to BOTH problems? I understand the need for 100% cotton.
I have yet to find a problem with TOO much vaseline. I keep the SOAKED vaseline cotton balls smooshed in little zip bags as well. When starting a fire, I take a bit and spend about 30 seconds fluffing it out as much as possible and then the fluffed out ball takes a ferro spark VERY easily and burns for quite a while.
I haven't tried this but I understand putting a bit of metal under the cotton ball will extend the flame even further since the melted petroleum jelly will not melt into the ground.
Am I missing something? Perhaps I am not trying the soaked cotton balls in sufficiently bad conditions that this error has yet to cause problems?