Recently - I got a phone call from someone who has just set up a her own home studio. Naturally - she is enjoying the freedom to torch when ever she wants, the luxury of not having to tidy up (as opposed to a shared, commercial studio), and the instant (well, almost) gratification of being able to see her beads as soon as the kiln has cooled down.
However, what she was not enjoying was that instead of the sparkling little gems that she was used to making, each bead, though perfectly formed and the envy of many - was a little dull, a little lifeless. Close inspection - with magnification - revealed a faint, subtle but visible, scum over the transparent glass, with a little pitting. She was at her wit's end trying to figure out what was happening. We discussed gas to oxygen ratios, her concentrator, the difference between natural gas and propane - adjusting the flame - nothing seemed to be the solution.
Finally - I said I would drop by and take a look at the set up - to see if I could diagnose it in person. When I got there, she told me, "well - this is embarrassing - I fixed it."
And indeed - the latest crop of beads were sparkly and delicious.
She changed to a fresh tank of propane.
That was it - the only difference.
So next time you are struggling with scum - consider your fuel source. Maybe a new tank of propane is in order?