rangerssuck fired this volley in news:47f35f7d-
:

Is there something better than old-fashioned glazing putty to seal
glass in wood sashes? I was thinking that maybe RTV silicone would do
better and last longer.

The common wisdom is to use siliconized acrylic caulk.

You cannot paint RTV silicones, nor paint any surface to which they've
been previously applied unless you sand down to bare wood again.

The siliconized acrylics are paintable, last well, and are strong (once
thoroughly dry. They shrink somewhat more than glazing putty, and are a
bit more difficult to remove in the future, but work quite well.

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On the comment about failed silicone -- yes, that might be it. I wish I
knew how to cause it to fail in just that way (if that's the case),
because it is a superior window-to-steel-door sealant in that condition.

LLoyd