Interesting failure mode...

--Had to do some silver soldering the other day so I got out my nifty little air-acetylene torch. Trouble started when I couldn't get it to ignite, despite nice shower of sparks from the sparker. Turns out some mud wasps had built a nice little plug in the end of the torch tip! Got most of the gunk out but it still doesn't work. Went to Praxxair (where I bought it) to get parts a new tip but the guy at the counter was clueless. The boss finally came out, said they don't stock parts any more, the torch was obsolete but they could order parts. Ho hum. Went back home and switched to propane torch and lower temp silver solder but this didn't work because all I have is the higher temp flux; they were also out of the liquid flux at Praxxair (I looked for the stuff when I was at the store but every type of flux they stock seems to have been rebranded Praxxair. Sounds to me like they're trying to develop a one-brand store: not good! Anyway it was an interesting but frustrating afternoon. I'm wondering if it might be possible to make my own flux out of lemon juice or some such. Suggestions appreciated.