I have, in the past, had an issue with what I assume is the insulation between the drum and the roaster’s body. It appears that some of the insulation has fallen apart a little bit. I actually had some of it fall into some of my coffee once. I assume this happened by my having beans fall through that slot between the drum and the glass and then rubbing up against it. I haven’t had this happen recently as I’ve begun vacuuming that space between each roast.
I thought about responding below, but I’ve had an issue with the insulation and not just a curiosity…
At any rate, I’m wondering if I need to think about replacing the insulation? Any thoughts?
Yes the Mica tube can de-laminate if beans get stuck between the drum and the tube and starts scraping against is. You can remove the drum and check the damage. A few layers of Mica coming off is not a problem. I would remove the damaged layers and vacuum / wipe it clean, then reinstall the drum.
As you mentioned it helps to vacuum the front after each roasts, so nothing gets between the drum and Mica.