Chimney Glaze

[BrotherBart]

Ok, I know the answer in a perfect world but here goes anyway. With all of the talk in my neighborhood about me lining my flues, one of the neighbors wants to do his too. I went up and took a look at his clay tile masonary chimney and it is the same as mine, 11X7 inside 12x8 outside. The chimney has a paper thin, and I do mean the thickness of a sheet of notebook paper, glaze of hard creosote. I took a pocket knife and chipped off some to the tile to see how thick.

If he lines this thing is he really looking at the exploding chimney adventures that Karen Duke talks about? Or if the liner sets this stuff off is he just going to have a seven or eight hundred degree cook-off that probably won't even be noticed? And if he lines it with the crap in there should he hold off insulating the top for this season to give it a place to go if it does light off?

If I was in a liability situation like a dealer I would tell him it has to be as clean as a fall morning. I actually believe it ain't gonna hurt anything.

 

[Todd]

When I lined mine I had the same thing. Local sweep said it would be fine and it would be real difficult to get all the glaze off. I just ran a brush up and down as good as I could. So far so good, no explosions yet.

 

[webbie]

Almost impossible to get that thin glaze off...it's baked on like powder coat paint.

I agree with Todd....if it is not in bog gobs, you are prob. OK.

 

[jabush]

The guys who lined my chimney did not brush it first(of course they didn't secure my Tee to the stove either, so...). I don't know if it didn't need it...or if they were not worried about it due to the wet mix they poured around the liner. I'm thinking once the wet mix sets up, it creates a dense, solid mass between the liner and the flue tiles. If the liner did generate enough heat through the solid insulation to touch off creosote, I don't believe there would be enough air for it to combust. Now as far as other types of insulation...I don't know. I seem to be one of the few on here who had the wet mix poured as insulation.
Also, who is Karen Duke and what happened to her chimney???

 

[elkimmeg]

Karen Duke was an active member here, that advertise on this site ( Victoria Fireplace ) One of the sites oldest menbers, that has not posted in quite some time. They also restore older brick chimneys and fireplaces. One brand stove she sells is the BUCK line
Her location is in VA

 

[jabush]

Thanks Elk. I did a search and found her website.

 

[webbie]

It's usually a good idea to sweep before a lining....that is, assuming there is something to sweep out. Our guys always used to bring along hte sweeping equipment, and we would do it if needed.

I agree that it would be near impossible for creosote to ignite which is around your poured cement.

As Elk says, Karen is a very experienced member who started out in the chimney business. She therefore has an insight that many dealers lack.

Concerning the subject at hand, we should be aware of a few things....

Yes, the chimney industry is/was guilty of trying to scare the public with the "get our of the house now" type of advertisement...but, truth be told, this was a very real possibility with heavy users of the older stoves. In 4-6 weeks, enough tars could be built up to create a nasty chimney fire. This is MUCH less likely with modern stoves.

There are various types of chimney deposits with different levels of danger. The worse is what I call "tar", which looks just like roofing tar and tends to BOTH glaze the chimney and also build up in small gobs - this is probably because it softens up as it heats and flows down into formations.

As much as I used to discount the danger, I have seen this stuff catch on fire and it is truly amazing! A relatively small amount if it can cause a nasty surprise - although it needs the other factors such as high temp to ignite and plenty of air to continue burning.

Many of the other types of chimney soot do not burn at all - in fact, most are the product of creosote that has already burned. Large formations of easily breakable creosote are usually composed of ash and tar mixed - my guess is that it is creosote which has ignited but then gone out due to not enough air. I think it would be tough to ignite this again.

Then there is ash and flyash, which cannot be ignited at all. They still classify this as creosote or soot....I could call it soot or fly ash.

Given that any hot fire needs LOTS of air, a tight installation becomes even more important and you can start to see why Elk and others are always talking about tight block-off plates.