Cleaned the chimney

Mine looks that way. Now. May clean it today. The pipe looks smooth inside. I think its the cool exhaust gas and the really cold metal in the winter.

When we had our snow n ice I was running g wide open and had ice circles hanging from the cap for 2 days.

Cats are clean but I think the cap collects what's left.

I have a 3.5 cuft cat stove that I just put new cats in this year and burning wood that is 2 years old and 20% or less MC.

 

I may cut mesh out next winter and then reinstall or put a cap over it and just youll the metal down in the summer.

 

Lots of low , smolder 24 to 36 hour +
burns cause my cap to gunk up some too.
January was warm & shoulder burns like now amplify the
wood's moisture content

I don't get much creosote when I burn hotter.
drier 3 year wood for me helped a lot too

I clean & inspect mid winter & before a new burn season ,
just a good "peace of mind" thing for me.
Sometimes, a waste of time, nothing,
sometimes I get some creo.
Worth it for the long burns, great heat output & efficiency.

Part of burning wood, clean & inspect
& strive for drier wood

 

I've noticed this year, that after installing more Class A, the cap hasn't done the icicle thing this year.
Not sure why, but I'll take it.

 

It was hard not having icicles forming when it was constantly sub zero! I burned the stove hard one day to try and thaw them off the cap with no such luck.

 

I was half expecting that with more pipe outside and colder temps, that 'd have a big problem this year with icicles.
Hasn't happened.

 

Our mesh screen under the cap had some creo buildup too yesterday when I went up to brush/sweep the flue. But not as bad as your picture, swags - it was still breathing fine. The buildup was typical (oddly, same in mild winters as in Arctic deep freeze like this). I expect this from our finicky VC Encore downdraft cat stove, but always thought the BK's did a better job of consuming the unburnt gasses before they left the stove.