# Discoloration of chimney pipe



## jarvis (Feb 12, 2010)

Hi all,
I finally fired my wood furnace for the first time this past weekend. It's a Woodchuck 2900 connected to about 30' of Supervent 8" class A stainless chimney pipe. I unfortunately got some wet wood that had been sitting outside under the edge of a roof, so I couldn't get a very hot fire going. My flue temp only reached about 200 degrees and I only had about three pieces in the firebox before I realized it simply wasn't going to burn hot enough to get a decent fire going. So, after about an hour or so I raked the pieces apart and blew the fire out rather than let it smolder all night. 

A few days ago I was leaving for work and noticed my chimney pipe is now discolored at the top, right below the rain cap and only in this one spot. I took a picture this morning but the sun was just rising so it's a little dark...but I had to leave for work so it's the best I could do. The spot is maybe 6"-8" large and is bluish in color, the same type of blue you see when chrome is overheated. It doesn't seem to extend below the chase cap and I can't see anything inside the chase. What could have caused this? The fire only burned for a little over an hour and never was that hot...I can't see how there would have been enough heat way up there to discolor it like that. I'm going to pick up a couple cords of dry wood this weekend but I'm concerned about what this bluing means before I fire it again. Does this pipe normally discolor through normal use, or do I have other problems?


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## shoeboxlen (Feb 14, 2010)

I dont run stainless but my regular pipe that connects to my chimney discolored due to the heat from the fire. I would not worry about it heat will cause a discoloration.


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## tbsdolmar (Feb 14, 2010)

Was the wind blowing? Mine gets that way when the wind blows fairly hard.


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## jarvis (Feb 14, 2010)

I don't remember if the wind was blowing that day. I don't understand how there could have been enough heat way up there to turn it blue. That was my main concern, I didn't think the outside of a class A insulated pipe should get that hot to where it would cause discoloration (assuming the heat came through from the inside). I've been gone to work all week during the daylight hours so I hope tomorrow I can get a better look at it.


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## ewdudley (Feb 14, 2010)

It sure looks like discoloration caused by heat, but given the batch of wet wood involved it would have to be creosote and/or related gunk condensates from smoke roiling in the vicinity of the cold metal on the outside of the flue.


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## 101x81 (Feb 14, 2010)

ewdudley said:
			
		

> It sure looks like discoloration caused by heat, but given the batch of wet wood involved it would have to be creosote and/or related gunk condensates from smoke roiling in the vicinity of the cold metal on the outside of the flue.




i agree with ed, if that was by overheating, the flue should be dark from bottom to top. mine look the same and there is not a trace of creosote inside but a very very light coat of dust, coffee colored.


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## trailhound68 (Feb 14, 2010)

I discolored my stainless insulated flue when I left home with the ash door open. That chimney saved my garage. I returned to find an empty fire box and a 
discolored pipe about 15' of 20' total. I'm a firm believer in Metal-Fab, the mfgr.
Is it possible that small section lacks insulation? Mine shows discoloration near to the boiler and lessens to none towards the top sections where it's cooler.


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## berlin (Feb 14, 2010)

That discoloration is NOT from the stainless getting hot. That's the direction the winds were blowing when you had a fire. It is cold outside, the moisture in the exhaust gasses condensed w/their burden of tars and soot and left a small stain. C'mon people, have you never seen a chimney stained in the direction of the prevailing winds, industrial, residential, or otherwise?


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## jarvis (Feb 15, 2010)

I finally saw it today in better light. The only time before I was able to see it was in the morning when I left for work as the sun was just rising. The spot is on the west side of the pipe, so it was always darker on that side and it gave the illusion of the pipe being blue because of the direction of the sun. When I got home from work it was dark, so it wasn't until this afternoon I was able to view it in direct sunlight. It does look more like a soot stain, the blue appearance was apparently just an illusion because of the direction of the sun and time of day. Thanks for the replies.


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