I'm planning a Bryce 5 animation of hot air balloons flying by twilight.  Not having used Bryce in quite a while, I find that I'm having a problem with simulating the internal glow of a balloon when its burner is lit.

I initially thought I could put a light inside of the balloon (which I would turn on and off periodically) and then play with the balloon's surface texture to allow some of that light through, but the only way I've been able to do this is to make the balloon partially transparent, which has the undesirable effect of making the whole balloon transparent.  It should be opaque save for the effect of the internal lighting "leaking through".

I also tried discarding the internal light object and instead increasing the ambience of the balloon itself with a yellowish ambient color selected, but that doesn't seem to be visible in darkness, even with ambience set to 100.  (Is Bryce ambience not truly ambient?  I would expect a 100% ambient object to show up very brightly in the dark.)

Can anyone point me in the right direction here?