Focomat Ic- how hot is too hot?

I get a little worried by the heat generated by my Focomat Ic during marathon printing sessions, but I REALLY wonder what the limit is when making very long single exposures into the ten to twenty minute and over range. I tend to use a 150W bulb, btw. I thought about placing IR absorbing glass above the condensers, but the absorbed heat is still in the enlarger....

I just checked an on-line manual for this enlarger:

members.cox.net/leitzleica/Manual.html

and found that the recommended bulb is 75W. Furthermore the enlarger head does not have a heat-absorbing filter as standard, and of course the bottom surface of the condensers makes direct contact with the film being printed, so there is potential for damaging this. What is more, excess lamphouse heat may cause the bulbholder to melt or distort, with the potential for a short-circuit to the all-metal frame of the enlarger. A very crude measure of excess temperature is smell - if the lamphouse enamel is smelling, it's definitely too hot!

If it were my enlarger, I would not exceed the recommended bulb wattage. If exposure times are excessive, given that the Focomat holds negatives totally flat and unable to shift, I would use a high-quality f2.8 enlarging lens which is diffraction-limited (as most top-quality lenses are) and can therefore be used with confidence at full aperture.

Regards,

David

if it has any plastic in it at all, i would use a cooler bulb. I have a beseler 67 whos head was completely melted and the dichro filters fused together.
Of course this was because my daughter who was 6 at the time turned it on and it was left overnight =].
(anyone want a beseler 67 for parts?)