Like the title says, I used nice balmy 45 degree day to do my mid season cleanout. I was happy to see barely 1 cup of buildup between both my stovepipe and chimney. I've had a few fires that I just couldn't get going this year and thought there would be more. One thing I saw different than years past, just the edge of the single wall pipe going into the thimble has some of that nasty shiny stuff. We're talking just enough to notice. Any reason why it would build up just there? I'm guessing it's because that's where the warm fuzzy indoors meets the extremely cold outdoors, but any insight would be appreciated. Should I replace that piece to be safe? I doubt that part of my stove pipe would ever get near the 500 degrees needed to ignite it. I usually burn between 350 to 400.