Less creosote (soot) on stainless steel pipe than black single wall

[PA. Woodsman]

I took apart the 7 1'2 feet section of black single wall pipe that is inside the house to see what shape the elbow was in, I had discussed this a bit ago and I was able to just clean it up and it should be good to go for another season, took it to the local stove shop and they said it was solid yet just some surface rust so I cleaned that up. I also cleaned the pipe, it wasn't real thick with deposits and it came off like dust as usual, no glazing at all because I burn dry wood at somewhat hot temperatures. I took a look up into the section of stainless steel pipe that is outside the house and noticed that it also wasn't bad at all, in fact it had less buildup than the inside black single wall pipe did so I left it go. I've been burning since 1989 and can clean the pipe every few years, it's never been an issue and this light coating isn't going to matter until at least next year, but my question is why do you think there is more buildup on the single wall pipe that is indoors than the thicker stainless steel pipe that is outside?

Thanks!

 

[ABMax24]

The single wall pipe is un-insulated and therefore cooler, these cooler temperatures allow creosote to build up. The outside stainless chimney pipe is insulated and will remain warmer, minimizing buildup.

It could also be a function of the surface finish of the material, the more polished surface of the stainless material may build less creosote compared to the rougher interior finish of the single wall.