"I've been rearranging frames this spring, and have taken out about 6 or more frames that are what I think are too dark, and don't smell fresh. They have a slightly burnt odor. When I press of the comb it can be brittle.
What are some good signs that the comb needs replacement? And, can that comb be used for anything else?"
1~ too dark brood comb or comb for supers?
2~ don't smell fresh, burnt odor, brittle......................maybe from how they were stored or maybe mite treatments applied that affected it?
3~ good signs to replace?
my answer for myself, i have and have had brood comb 20 years old or older, and comb in supers the same age. beekeepers don't like to give drawn comb up, because of the work bees have to draw new comb out to replace old comb, and this takes away from brood and/or honey production.
brood comb is different than comb in supers (my ho), unless comb in supers has been used for brood rearing or the queen has layed up in whatever honey super frame year after year with no excluder on, and we can tell the difference. the cells or frames are much darker.
good IPM practices is to change out frames. BROOD FRAMES. i change frames out every year, (one at a time) and sometimes very reluctantly. when i can't see through a frame and it is blacker than black, the frame gets marked to rotate out, and i know it needs to go.
honey supers........i don't change out frames of honey supers very often. but i use queen excluders.
you are young in beekeeping jen, not sure how these frames: brood, or supers have a burnt smell to them? brood frames naturally get dark, and overtime they get very dark. like i said/asked perhaps the burnt smell is from mite treatment or storage?
i agree with ef, any honey stored and capped in brood comb, will be darker, the comb affects the color.