i was taught to work the metal at bright orange.....if you use the horn of your anvil, be sure to line the squareness of the way you bend ...cause the horn is tapered you wont get a nice even turn on the peice. ... you do get more scale in the gas forge...the changing of the color of the exhaust, and the water drop thing...where are you getting your metal?? the color sounds like your burning off some coating or maybe some old flux is lighting up.... i leave a scrap[ piece in my propane to set items on so it heats more evenly...that piece of metal goes thru lottsa of heatings and does form an inordinate amount of scale on it, i dont care cause its a sacraficial piece of scrap...when you chip the scale away the metal is ooce and shiny...it would be interesting to weigh a piece and reheat it many times to see how much mass you would loose.....i digress