Hot bricks & Tar Buildup

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fatjay

New Member
Oct 15, 2014
37
Eastern PA
I switched over to hot bricks in my clawfoot wood stove last year, as I am away a lot, and it's much easier for my wife to handle than an arm full of wood.

Last year I had a great experience, everything went well. This year I picked up a pallet and brought them home, and for the past week I've been burning left-over's from last year. Last night, however, I threw on some of the new stuff. It was noticeably different, the packaging, the size of the bricks, and the feel, even though it was the same company.

This morning I come down and open the stove, to toss a few more on before heading for the shower. When I opened the door, I was shocked to find tar stretching from the door to the stove like bubble gum. This is the first time I'd seen it like this.

Has anyone else experienced something like this with the bricks? Never had the issue before.

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Holy yuck! That looks like a combo of bad fuel and low oxygen environment. I have yet to hear of a complaint about brick fuel not being dry, but I suppose this could be the first. Strange.
 
wow that is a nasty looking cawley. where where the old bricks stored over the summer? They can take on a lot of moisture if in a damp environment. But that looks like more that damp fuel to me what is the rest of your setup like?
 
Yuk. That is really odd. Normally if a brick fuel is wet it will fall apart into sawdust. If you cut one of these bricks open it is damp inside? Definitely call the manufacturer and tell them. You may have a bad batch of fuel.
 
They definitely aren't wet, I've seen what happens when they get wet. I ran the past week on my last batch of hot bricks with no issue, then last night these. I'm at a loss. I called my supplier and he said he's had a lot sold in the past few weeks but hasn't received any feedback.

Cleaned everything in the spring, then again a few weeks ago to make sure nothing had decided to make a home there over the summer. All is crystal clear for the season and burning well. Keeping at a steady 400-500F which is about 2-2.5 on my flue dial.
 
fatjay said:
400-500F
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Where are you taking those measurements? Regardless i am sure that you were well below those temps anywhere in the system to get that mess. Can you describe the flue setup? Have you checked it after seeing that mess? The only thing that i have seen that could come even close to that is a blocked flue.
 
What does your chimney cap look like, stained? plugged? normal?
 
bholler said:
Where are you taking those measurements? Regardless i am sure that you were well below those temps anywhere in the system to get that mess. Can you describe the flue setup? Have you checked it after seeing that mess? The only thing that i have seen that could come even close to that is a blocked flue.
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You have the same stove as me, just larger. My air is controlled by the draft wheel on the front, and my temperature is from the rear burner on top. My chimney cap looks normal, it's fairly open.
 
Totally at a loss here, I would send the chimney brush down the chimney and verify there's no blockage of any type any where in the system.
 
fatjay said:
You have the same stove as me, just larger.
Click to expand...
yes i know i work on several 400s. What are your pipe temps at? What is your startup and loading procedure? I am just running though any possibilities because that is a huge mess and i am not sure what could have caused it yet. What type of chimney do you have what size how tall ect?
 
Supposed to be in the 60's for thanksgiving. I can't imagine what it could be. Bricks are dry, airflow is good. Unless, what if one of those bricks split in half and expanded, falling against htat slot at the front door blocking the air? They expand when they burn I've noticed.

I load in 6-8 at a time, 2x2x2 typically fits rather well. Start-up I use a fat log and news paper. News paper burns fast giving that initial burst of heat to get the draw going, then the fat log provides the rest of the heat and ignites the bricks. I've been burning around the clock for the past week though, haven't stopped since I started on the evening of the 18th.

Chimney is double walled 5" ID and insulated, goes right out the wall behind the stove, then strait up past the second floor by 2-3 feet. My cap is not in great shape and falling apart, but causing a less restrictive pass instead of a more restrictive pass. Could that have anything to do with it?
 
fatjay said:
I load in 6-8 at a time, 2x2x2 typically fits rather well. Start-up I use a fat log and news paper. News paper burns fast giving that initial burst of heat to get the draw going, then the fat log provides the rest of the heat and ignites the bricks. I've been burning around the clock for the past week though, haven't stopped since I started on the evening of the 18th.
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ok at what temp do you start to shut down? what is the temp of the stove pipe?

fatjay said:
Chimney is double walled 5" ID and insulated, goes right out the wall behind the stove, then strait up past the second floor by 2-3 feet. My cap is not in great shape and falling apart, but causing a less restrictive pass instead of a more restrictive pass. Could that have anything to do with it?
Click to expand...
Have you confirmed that it is not plugged since this incident?

fatjay said:
I've been burning around the clock for the past week though, haven't stopped since I started on the evening of the 18th.
Click to expand...
What do you do when you reload? How long have you been burning this setup? what does the dirt you usually take out after cleaning look like?
 
your stove top temps are a little low also. I typically go by pipe temp so i just went down and checked with my pipe cruising at about 275 my top is 700 on the front burner and 650 on the back
 
When I first start, I have the door open until there's a good roar, then close it down and set it at 4 until the temp comes up to 400 or so, then dial back to 2 which provides enough air to maintain 400-500 for a solid 5-6 hours on 8 bricks. When it drops down to 200-250, I'll open the door, spread the ashes, and reload, add a fat stick, and set it at 4 for 10-15min, plenty of time to get back to 400+. The only time I'll do a partial load is if it needs it around 6pm, I'll load 4 or so, just dropping them in, and it'll last until 10 when I'll load with 8.

The cap got blown off during a storm this past summer, as a result it's bent up a bit, sort of a 45 degree. There's no blockages, as I've been in there since then. But in my mind it would let the air escape more quickly than a flat cap, maybe causing a more rapid draw on air, cooling the front of the stove, causing the buildup?

My thermometer hits red at 500, my pipe off the back is horizontal, and the thermometer doesn't get a good reading on it for whatever reason. It goes strait out the side of the house, I don't have a vertical shaft inside. My chimney starts pinging around 600, so I try to stay under that. My burn zone according to my thermometer is 300-550.
 
I don't know what the pinging of hte chimney means, but I assume it's not good. Pinging is the wrong word. It's more like pouring dry rice on plywood? Or crinkling tin foil?
 
fatjay said:
My burn zone according to my thermometer is 300-550.
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That is for the pipe not the stove top. And yes it will ping a bit as it comes up to temp. What do you mean it does not get a good reading if you put the thermometer on there and it is working it should give you a good reading. When i load mine i have the dial at 10 till my pipe hits 400 or so then shut it down to 7 to hold it there for about 10 mins then shut it back to about 3. At that it cruises nicely with the pipe at 250 to 300 where it should be. Now the dial numbers will vary allot depending on fuel and chimney height so yours will be different.
 
fatjay said:
I don't know what the pinging of hte chimney means, but I assume it's not good. Pinging is the wrong word. It's more like pouring dry rice on plywood? Or crinkling tin foil?
Click to expand...
That is perfectly normal. You are hearing the pipe expand and probably hearing some of the buildup in your pipe pulling loose and falling. If you start burning at higher temps you wont hear the crinkling as much just some pings
 
My rear pipe is hard to read. On top you have to be standing over it to see, and on the side it falls off. It also reads about 100F when the stove top was 500F, which felt to low to me, like it wasn't making good contact.
 
I was under the impression that 700F at the stove top was to high and could cause the cast iron to break. If it's safe, I'm more than willing to give it a try though, see what happens.
 
fatjay said:
On top you have to be standing over it to see, and on the side it falls off. It also reads about 100F when the stove top was 500F, which felt to low to me, like it wasn't making good contact.
Click to expand...
is it single wall pipe coming out the back?
 
Single wall out the back, 2' and into the wall, horizontal.
 
fatjay said:
I was under the impression that 700F at the stove top was to high and could cause the cast iron to break. If it's safe, I'm more than willing to give it a try though, see what happens.
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nope 800 is typically the start of what most consider over firing. 700 is fine. I would get a new thermometer and put it on the pipe. If it really is 100 that is obviously a problem. and it should stick to the side no problem
 
You mentioned that your cap got blown off and damaged in a storm this summer resulting in the top being bent at a 45 degree angle. You think that would allow exhaust gas to escape easier, rather than pose some sort of restriction. That sounds logical on a calm day; however, what if you had some wind blowing in the direction that would cause the bent cap to funnel the air straight down your flue? If that happened and the exhaust gasses got stopped or greatly slowed down do you think it could cause your bricks to just smolder and produce that tar like substance you got?
 
If it isn't nasty outside I'd be tempted to make a 3 brick teepee outdoors with these new bricks and see how they burn. The idea that the intake got blocked may be worth checking out. Maybe try putting in one less block next time so that there is more room in front of the intake?
 
I think that over all you are not burning hot enough but that did not cause this one time huge mess. Something had to have changed to cause that. I persoanlly would take everything apart and confirm that the intakes the pipe and the chimney are all clear
 
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