Tai Goo - around 1000-900f I lost any hint of a red glow. This is inside a vertical forge I just built with doors in place that left only a 2"x3" access hole - this is in my "forging shed" set in Western Oregon woods - so even on a sunny day there's no direct sunlight.
Anything that sits still for too long around here grows moss. Or algae.
Kevin - while I seem to be more anal about details than most in the 5160 Club out here - I'm loving getting serious about bladesmithing as a TOTAL alternative to the 1/3 century I've spent setting up databases and designing & coding office & shop floor programs. I've been making my living on all those little 1s and 0s - - - and it is a delight to make something physical from fire, steel, hammer, and quench - even if I have to wrap my old brain around phases, alloys, IT charts and all that! I couldn't do it without the generous help from folks like you, forums like this, and our local knife maker support club - and local Grand Old Man Goddard!
p.s. I'm not joking about the moss and algae.