Unseasoned wood or too cool of a operating temp loger , that's the only cause of such accumulating . Ocurrs often especially when green wood is used or the stove damper throttled back . Secondary cause , when uninsulated chimneys cool down the cooler internal temp can allow creosote to accumulate brother !

Thanks! Your Info explains a lot as to why this was my first to see since the 1980 install.

1. When I went back to clean it was not as bad as what I initially saw. I went up to Ck/Service a Turbine Rotating Noise. Plus, it was too Cold vs My Work Habits…

2. I feel this was not a 1st but my 1ST to see vs the 6’ of Insulated 12” ID Pipe to Show this.

3. The Pipe has been Basically Self Cleaning sitting on a 6’ High Firebox with Hot Fires.

4. My Firewood Collections off the Curbs has continued to supply wood with help.

5. Our Old Neighborhood has so many Large Trees being Trimmed X Plenty Wood.

6. Most Small Trimmers will give you “Cut To Length Wood Close” vs Paying. To Dump…