Fire brick observations

[Easy Livin’ 3000]

Cleaning out the stove ahead of season 3. Tasks include removing refractory and deciding how many replacements we need.

Most are in excellent shape. Three of the full bricks and all three cut bricks all have some splarging (see picture). They were all located in front of the doghouse. I've surmised it occurs due to thermal shock- cool air washing over the hot bricks.

Called around to the local fireplace shops and masonry supply houses after some time doing interweb searches. Here's what I found:

Best: local masonry supply- $1.68
Worst: big box stores- $39 for box of 6
Local fireplace store- $4.

I'm going to put the full bricks with the splarging in the back with the damaged part facing the outside, tucked under the retaining clips. For the partial bricks, I'll just flip them over, splarging side down. Good for at least one more season. I'll grab a half-dozen when I'm in the neighborhood of the local masonry supply

 

[WoodyIsGoody]

Cleaning out the stove ahead of season 3. Tasks include removing refractory and deciding how many replacements we need.

Most are in excellent shape. Three of the full bricks and all three cut bricks all have some splarging (see picture). They were all located in front of the doghouse. I've surmised it occurs due to thermal shock- cool air washing over the hot bricks.

Called around to the local fireplace shops and masonry supply houses after some time doing interweb searches. Here's what I found:

Best: local masonry supply- $1.68
Worst: big box stores- $39 for box of 6
Local fireplace store- $4.

I'm going to put the full bricks with the splarging in the back with the damaged part facing the outside, tucked under the retaining clips. For the partial bricks, I'll just flip them over, splarging side down. Good for at least one more season. I'll grab a half-dozen when I'm in the neighborhood of the local masonry supply.

Thanks for the detailed report!

Do you know whether the firebricks you quoted are of the same manufacturer? I'm far from an expert on this and would like to know more. Because I've seen so many fire bricks of varying quality (besides simply pumice/non-pumice). Some are complete crap, others last and last and last. And that's quite a price spread in the bricks you quoted.

My strategy with firebricks has always been to not remove them without a good reason. Even cracked ones were allowed to stay unless the crack was such that it might fall out or the brick was in danger of completely disintegrating. I've even been known to re-install cracked ones (that needed to be temporarily removed for some other reason) as long as the crack was such that it wasn't in danger of falling out.

Finally, are you trying to invent a new word, "splarging"? I think the word you might be looking for is "spalling".

 

[byQ]

ED 3000, I built a masonry heater and studied up on fire brick. I learned that all fire brick aren't equal. I had the opportunity to buy fire brick that was classed as 'super duty'. My cost was the same as if I bought 'low duty' firebrick. A good choice? Should I buy the super duty? Usually low duty bricks are used. What you find in box stores and fireplace supply stores are usually the lower duty bricks.

So I began studying up on fire brick and asked a few masons about fire brick. What I learned: the brick come in 3 general ratings, 1) low duty, 2) medium duty, and 3) high/super duty. I asked, what's the difference? In general the difference is the amount of alumina (metal) vs sand in the brick. The more metal equals heavier, and the higher the duty status (and usually higher in cost).

Mason1 argues with Mason2,

Mason1: You are better off buying low duty firebrick because the higher sand content makes the bricks more flexible to the constant heating and cooling that occurs in wood stoves, and these bricks are cheaper and lighter. The higher duty brick will crack because they are so dense they don't do well going from hot to cold to hot.....they are made to stay hot all of the time - like in incinerators.

Mason2: Baloney! There is no proof that medium/high/super duty bricks will fracture going from cold to hot to cold ....... These heavier bricks are tougher, too. They will last longer against the constant forces of having firewood thrown onto them. Buy super duty if you can, or at least medium duty. Those low duties will wear out after a couple of years.

Mason1: Well maybe. Why spend more when the low duty bricks are good enough? And besides when you get into putting higher duty status bricks in your wood stove you are changing the wood stove because these bricks are more dense. The stoves were made to work with low duty bricks. The higher status bricks will cause the stove to overheat.

Mason2: What, there's no proof! The higher metal content of these bricks will allow the heat to escape faster, so the opposite is true. You want to warp your stove? - put insulating fire brick in it. The heat won't be able to get out. The low duty bricks are more insulating!

Mason1: Yes but the denser bricks will hold more heat which will cause the stove to get hotter. Go with what the manufacturer put in the stove originally.

Mason2: They only put these low duties in their stoves to cut down on cost. I would spend a little more for the 'better' bricks.

In conclusion, most masons are putting higher status fire brick in masonry heater fireboxes because they last longer/can take more abuse. But they use lower status bricks in other areas because they are cheaper. Wood burning isn't really much trouble for any class of fire brick. But all of this is something to think about.

 

[Easy Livin’ 3000]

Thanks for the detailed report!

Do you know whether the firebricks you quoted are of the same manufacturer? I'm far from an expert on this and would like to know more. Because I've seen so many fire bricks of varying quality (besides simply pumice/non-pumice). Some are complete crap, others last and last and last. And that's quite a price spread in the bricks you quoted.

My strategy with firebricks has always been to not remove them without a good reason. Even cracked ones were allowed to stay unless the crack was such that it might fall out or the brick was in danger of completely disintegrating. I've even been known to re-install cracked ones (that needed to be temporarily removed for some other reason) as long as the crack was such that it wasn't in danger of falling out.

Finally, are you trying to invent a new word, "splarging"? I think the word you might be looking for is "spalling".

This will be season 3, not 24x7, but we probably provide 90-95% of our heat from the stove.

I make up words all the time, my goal being that the reader understand what I'm talking about. Someone needs to help the language evolve. I'm way more qualified than most to participate in the evolution. ;-)

 

[Easy Livin’ 3000]

ED 3000, I built a masonry heater and studied up on fire brick. I learned that all fire brick aren't equal. I had the opportunity to buy fire brick that was classed as 'super duty'. My cost was the same as if I bought 'low duty' firebrick. A good choice? Should I buy the super duty? Usually low duty bricks are used. What you find in box stores and fireplace supply stores are usually the lower duty bricks.
So I began studying up on fire brick and asked a few masons about fire brick. What I learned: the brick come in 3 general ratings, 1) low duty, 2) medium duty, and 3) high/super duty. I asked, what's the difference? In general the difference is the amount of alumina (metal) vs sand in the brick. The more metal equals heavier, and the higher the duty status (and usually higher in cost).

Mason1 argues with Mason2,

Mason1: You are better off buying low duty firebrick because the higher sand content makes the bricks more flexible to the constant heating and cooling that occurs in wood stoves, and these bricks are cheaper and lighter. The higher duty brick will crack because they are so dense they don't do well going from hot to cold to hot.....they are made to stay hot all of the time - like in incinerators.

Mason2: Baloney! There is no proof that medium/high/super duty bricks will fracture going from cold to hot to cold ....... These heavier bricks are tougher, too. They will last longer against the constant forces of having firewood thrown onto them. Buy super duty if you can, or at least medium duty. Those low duties will wear out after a couple of years.

Mason1: Well maybe. Why spend more when the low duty bricks are good enough? And besides when you get into putting higher duty status bricks in your wood stove you are changing the wood stove because these bricks are more dense. The stoves were made to work with low duty bricks. The higher status bricks will cause the stove to overheat.

Mason2: What, there's no proof! The higher metal content of these bricks will allow the heat to escape faster, so the opposite is true. You want to warp your stove? - put insulating fire brick in it. The heat won't be able to get out. The low duty bricks are more insulating!

Mason1: Yes but the denser bricks will hold more heat which will cause the stove to get hotter. Go with what the manufacturer put in the stove originally.

Mason2: They only put these low duties in their stoves to cut down on cost. I would spend a little more for the 'better' bricks.

In conclusion, most masons are putting higher status fire brick in masonry heater fireboxes because they last longer/can take more abuse. But they use lower status bricks in other areas because they are cheaper. Wood burning isn't really much trouble for any class of fire brick. But all of this is something to think about.

I'll ask about this at the masonry supply place when I stop in. Based on the phone conversations, I'm lucky to have found any locally. The most expensive ones I've found so far locally are boxed, vogelzang/us stove branded. These were available by the brick at tractor supply for $3 a pop. Clearly the light duty bricks.

 

[begreen]

Are the firebrick unusually light or normal weight? If they are light they may be pumice firebrick. These are more expensive but do a better job of insulating the firebox. SBI sells them for about $5 Canadian.

 

[Easy Livin’ 3000]

Are the firebrick unusually light or normal weight? If they are light they may be pumice firebrick. These are more expensive but do a better job of insulating the firebox. SBI sells them for about $5 Canadian.

They felt lighter when they were new, by my recollection. I think they are the pumice ones. Problem is, I'm fresh out of Loonies at the moment! Seriously though, shipping usually is the deal breaker on bricks.

 

[madison]

Thanks ED for the post.

I seem to be in the same boat with you and firebrick "length of service". I have used the OEM light weight "pumice" bricks in my PE T6 and have been very dissatisfied with them. Most of my issues are similarly located - around the ash chute and inlet baffle. My pumice bricks deteriorate in that area within a single burning season. I will flip them and rotate them to the sides of the stove to get another year out of them.

I have experimented with heavier bricks from Tractor supply and have had good luck with those not breaking down. I have been reluctant to using the heavier (and much less expensive) bricks throughout the stove due to some comments from other forum members.

I have been burning 100% locust for the past few years and believe that the extreme heat from the secondaries coming out of the inlet baffle leads to the breakdown of the pumice bricks. I will get large chunks of rock like "ash" on cleanouts in the area in question. My limited experimentation with the heavier bricks and locust,,,, i do not get these chunks, which leads me to believe the chunks are pumice aggregates or breakdown products of the pumice material...

 

[begreen]

That is odd. Do you use the ash chute? If so I am wondering if there's an air leak there. Ours has been sealed up with ash for a long time. Our bricks are the same age and are still original. Maybe try keeping more ash on the firebox floor? Last winter we burned about a cord of locust in addition to 2 cords of doug fir. The floor bricks still look ok. There is one cracked brick in the rear, but nothing serious yet. I am the one that cracked it by banging into it with a split during a reload.

 

[madison]

I used the ash chute once. I have actually considered sealing it with high temp adhesive, I do let it fill with ash and do not disturb it.

More ash in the firebox is a good idea and one that I have considered to be a source of my problem, I do tend to clean out the box at least once a week. Obsessive compulsive on the cleanouts is an issue.

 

[Easy Livin’ 3000]

Stopped by a fireplace store that I happened to be passing. $4 per brick, like the other local fireplace store. They were much heavier and denser than originals.

 

[begreen]

I used the ash chute once. I have actually considered sealing it with high temp adhesive, I do let it fill with ash and do not disturb it.

More ash in the firebox is a good idea and one that I have considered to be a source of my problem, I do tend to clean out the box at least once a week. Obsessive compulsive on the cleanouts is an issue.

Therein lies a difference. Our firebox gets cleaned out once a month, or more. That is one of the benefits of burning doug fir. It's quite low ash. I only burn locust when a) I have it and b) when it's very cold.

 

[Hogwildz]

3 years for firebricks is an unusually short life span.