Pumice Stone condition - thoughts?

[jpcjguy]

Hi all,

So I have a Boston Enviro 1700 and it is a couple years old. I have used it for 2 seasons and the previous owner probably 2-3. Here are pics of my pumice stones. How long should they last? They are pretty crumbly. Am I doing something wrong? Too hot? bad wood? New to all this.

 

[Prof]

The pumice bricks don't stand up well, even if you are easy on them. They apparently make the stove more efficient, but I replaced a few in my old stove with the harder and cheaper tractor supply versions. I didn't notice a difference. Are you leaving an inch or so of ash in the bottom when you are burning? Might help keep the bricks on the bottom in better shape.

 

[velvetfoot]

The back wall seems to get a lot of abuse. 5 years is about right.
I've replaced mine with standard, and less expensive, firebrick, which are more rugged and recommended by the stove dealer.

This might stir controversy amongst the hearth.com cognoscenti however.

 

[begreen]

Our pumice bricks will be going on 12 yrs. without replacement in the fall. I have cracked a couple and will move them to the floor, but overall these bricks have stood up well. I am careful not to abuse them and they still look good.

Jpcjguy, you bricks are spalling. It's hard to know their history before you. It looks like at some point some cracked side bricks were swapped out and put on the floor. The bricks have some more seasons in them. You can extend their life by not slamming wood into them and keeping an ash bed over them. Don't scrape aggressively when shoveling out ash. Leave a 1/4 -1/2" when cleaning out.

 

[Highbeam]

They suck but you aren’t supposed to replace them with the cheap and common nonpumice ones. It could affect the clearances or some other unlikely reason.

 

[begreen]

They suck but you aren’t supposed to replace them with the cheap and common nonpumice ones. It could affect the clearances or some other unlikely reason.

They're fine if not abused.

 

[bholler]

Honestly I find they last about the same if not more than standard splits. They are softer and wear away but they don't crack nearly as easily. And as far as cost goes we pay about less than a dollar more per pumice brick.

 

[jpcjguy]

So I did some reading on the differences in firebricks - and besides the fact that my head is swimming, it clearly seems like a "Ford vs. Chevy" debate when comparing the pumice vs. standard ones. Of course the Enviro part number firebricks are $$$$ so I won't be going there. Since I have an insert, not a free standing stove, is there any reason I can't use the standard ones from like Tractor Supply? Local options are limited here in Richmond, VA as it is not a big market for wood burning. My local specialty fireplace store does not even sell bricks!
The local brick supply does sell some - they are from Superior Clay - Firebricks and the guy said they are considered low duty for up to 2000 degrees and are $1.75 each.

 

[jpcjguy]

So I dug up my manual and it says "When replacing bricks, use only pumas type fire bricks". Obviously someone did not spellcheck , but is this based on performance or CYA? Of course I am out of warranty so no issue there.....

 

[bholler]

So I dug up my manual and it says "When replacing bricks, use only pumas type fire bricks". Obviously someone did not spellcheck , but is this based on performance or CYA? Of course I am out of warranty so no issue there.....

It is based on performance mainly but replacing them with standard brick would technically void the ul listing. But I really don't see any that need replaced there

 

[Highbeam]

Replace pumice with pumice. I find them inferior products but will do this to maintain the UL listing which is a good idea to have if your house burns down!

 

[bholler]

Replace pumice with pumice. I find them inferior products but will do this to maintain the UL listing which is a good idea to have if your house burns down!

Why do you think they are inferior? I find exactly the opposite

 

[Highbeam]

Why do you think they are inferior? I find exactly the opposite

I have found the pumice to be soft and fragile. Rapid erosion and chunks spall off when you remove clinkers. In my home I am currently running one stove with each type. Maybe our softwoods are harder on them.

Of course, I have a much longer burn season than most and the current bricks are almost 10 years old. It’s not like they’re made out of wonder bread but pretty close!

 

[bholler]

I have found the pumice to be soft and fragile. Rapid erosion and chunks spall off when you remove clinkers. In my home I am currently running one stove with each type. Maybe our softwoods are harder on them.

Of course, I have a much longer burn season than most and the current bricks are almost 10 years old. It’s not like they’re made out of wonder bread but pretty close!

Soft woods may be I don't know. I find the hard brick crack much faster than the pumice ones erode. For most of my customers. But either way unless you abuse them they last long enough it shouldn't be a big expense.

 

[Highbeam]

Soft woods may be I don't know. I find the hard brick crack much faster than the pumice ones erode. For most of my customers. But either way unless you abuse them they last long enough it shouldn't be a big expense.

Im not a wood “chucker” so I don’t have crack problems and maybe 10 years is just the average life expectancy for bricks. The high density bricks in the Englander look like new. Almost still glossy.

Talk about sweating the small stuff! On the bright side, pumice bricks should be easier to cut to fit. They’re really getting eroded in my BK.

 

[begreen]

Soft woods may be I don't know.

Nah, I only burn softwoods. Not an issue. I try to be careful about wood placement and not slamming in wood in a hot stove. I also need to dump ash much less frequently due to burning doug fir. But I probably burn 2/3ds the hours and fuel that Highbeam does in a year because we have the more efficient heatpump to cover swing season temps above 45º. Our bricks have at least a few more seasons left in them. If they get me to 15 yrs, they owe me nothing.

jpcjguy, they are sold online here:

Pumice Firebrick Splits 6-Pack

Pumice firebrick splits measure 4 1/2' x 9' x 1 1/4' ; the most common size for wood stoves.

www.stoveworld.com

 

[qwee]

The pumice type bricks are very different from regular type fire brick. They block energy, whereas regular fire brick absorb it (sometimes slowly). I would think one would be changing the whole burning 'chemistry' inside their wood burner by switching from one to the other.

The pumice bricks would probably force more heat energy out the top of the stove (if they were on the bottom and sides). Obviously the regular fire brick would provide more thermal mass which would even the heat out of your stove (but take longer to heat up and cool down). One could play with their burning chemistry by changing the duty status of their fire brick (if it was a regular fire brick stove).

If you are finding the brick in your stove getting damaged/chipped get a higher duty brick - they come in low, medium, and super duty. Generally, the duty status correlates to the amount of alumina (metal) in the brick. The higher the duty status the tougher the brick, and the heavier/denser the brick will be - due to having more metal in it. Super duties transfer heat more rapidly than a low duty brick (which have more sand and air voids, thus slowing down the heat a little bit).

Some worry that the super type bricks may crack easier because they are so dense - but some have used them and found them to work fine - but they cost more, and are probably overkill. The low and medium duty might be better in a wood stove because they have more internal give - thus when they are cycled through heating and cooling (like in a wood stove) they don't microfracture (because of the little voids in the brick give flex). But they chip easier.

 

[velvetfoot]

See, I told you it was controversial.

 

[stoveliker]

the

The pumice type bricks are very different from regular type fire brick. They block energy, whereas regular fire brick absorb it (sometimes slowly). I would think one would be changing the whole burning 'chemistry' inside their wood burner by switching from one to the other.

The pumice bricks would probably force more heat energy out the top of the stove (if they were on the bottom and sides). Obviously the regular fire brick would provide more thermal mass which would even the heat out of your stove (but take longer to heat up and cool down). One could play with their burning chemistry by changing the duty status of their fire brick (if it was a regular fire brick stove).

If you are finding the brick in your stove getting damaged/chipped get a higher duty brick - they come in low, medium, and super duty. Generally, the duty status correlates to the amount of alumina (metal) in the brick. The higher the duty status the tougher the brick, and the heavier/denser the brick will be - due to having more metal in it. Super duties transfer heat more rapidly than a low duty brick (which have more sand and air voids, thus slowing down the heat a little bit).

Some worry that the super type bricks may crack easier because they are so dense - but some have used them and found them to work fine - but they cost more, and are probably overkill. The low and medium duty might be better in a wood stove because they have more internal give - thus when they are cycled through heating and cooling (like in a wood stove) they don't microfracture (because of the little voids in the brick give flex). But they chip easier.

The superduty bricks do not contain aluminum (metal) but alumina (aluminum oxide). This is a pretty good thermal insulator at high temperature (and surprisingly a good thermal conductor at very low temps). There is no metal. The difference in thermal performance here, though, is indeed due to density differences.

 

[jpcjguy]

So I am coming back to this as the season will be here before I know it.
I figure I can flip some of them upside down and reuse. There were 2 cracked ones on the wall that I flipped and you can see the break line - hopefully that will hold for a season or two?
I took a pic of the one that is spalling pretty bad - it has lost some of its "thickness" but I figure I can still use it flipped correct?

I am going to order a 6 pack of these to replace a couple that just crumbled: Amazon product ASIN B00XC1YCTY
I have to cut two down to 3" wide - for the back row on the bottom - figure an angle grinder should do it ok.

Thanks all!

 

[Hoytman]

What about WoodStock stoves and their UL listing? Some of their stoves come with some type of bricks or soapstone. I highly doubt UL tested their stove in both configurations just to satisfy WoodStock wanting to give customers an option. Maybe they they did, but I doubt it.

Any type of bricks likely need seasoning or broken in. That is, cured just like the paint except this curing drives any moisture in the bricks out.

If your stove sits any time at all unused for a season, with the stove pipe left in, then there’s a good chance moisture has again infiltrated the bricks some. The “cure” for that would be a couple small fires to again drive any moisture out of the bricks. Once that is done, stoke it up.

Anyway...it all sounds good. LOL!

 

[Hoytman]

It does seem some pumice stones seem to last while other do not. I still think it’s a moisture issue. Them again, I have seen a lot of pictures of Quadra-fire bricks just turned to dust and seemingly in stoves with little use. Oh well. Bricks of any type are cheap.

I have read that some bricks absorb heat and protect the steel of the stove while other types of bricks like pumice reflect heat back into the firebox for better efficiency. Seems like those might further protect the steel.

Often thought of replacing clay bricks in a stove with soapstone, OR leaving in the bricks and adding an additional layer of soapstone just to play around and see what changes. Of course, this would be done on a test stove outside before doing it in the house.

 

[stoveliker]

To my understanding UL only tests the configuration that the vendor pays for. It has nothing to do with what UL likes to do or not. Getting one unit tested can easily run into the tens of thousands of dollars. I f the stove is UL listed with both types of stone, it has been tested with both types of stone. At the price for each test.

 

[Hoytman]

I’d like to see some hard evidence of that. Reason being, many of us are well aware how the stones can change the burn characteristics of the stove. Not saying you are wrong. I just happen to think that stove performance would be substantially different and even mentioned in brochures. I can’t imagine stones not extending the heat life of a steel stove and WS not mentioning it.

Aren’t they lined all the way up the inside of the stove sides and back instead of just one brick high in the sides and back? Aren’t they available with regular bricks and lined that way as well as available with soapstone inside that way? I’m not sure if they are, but I thought they were. If the stones didn’t change performance then why offer them as an option? If the performance isn’t changed then it really doesn’t make sense to offer them lined that way. Especially at the cost difference. If the performance is changed then why isn’t listed?

Surely if both configurations have been tested as you suggested one would think there is a benefit to it and that benefit would be mentioned in some sort of brochure listing the performance difference. Doesn’t make sense to offer a stove with a “liner” option just because they’re soapstone if they don’t offer any significant difference in performance.

I don’t mean to sound argumentative. I’m just thinking out loud and asking questions I don’t have the answers to. Would be nice to see some concrete evidence if there is any.

 

[bholler]

I’d like to see some hard evidence of that. Reason being, many of us are well aware how the stones can change the burn characteristics of the stove. Not saying you are wrong. I just happen to think that stove performance would be substantially different and even mentioned in brochures. I can’t imagine stones not extending the heat life of a steel stove and WS not mentioning it.

Aren’t they lined all the way up the inside of the stove sides and back instead of just one brick high in the sides and back? Aren’t they available with regular bricks and lined that way as well as available with soapstone inside that way? I’m not sure if they are, but I thought they were. If the stones didn’t change performance then why offer them as an option? If the performance isn’t changed then it really doesn’t make sense to offer them lined that way. Especially at the cost difference. If the performance is changed then why isn’t listed?

Surely if both configurations have been tested as you suggested one would think there is a benefit to it and that benefit would be mentioned in some sort of brochure listing the performance difference. Doesn’t make sense to offer a stove with a “liner” option just because they’re soapstone if they don’t offer any significant difference in performance.

I don’t mean to sound argumentative. I’m just thinking out loud and asking questions I don’t have the answers to. Would be nice to see some concrete evidence if there is any.

If they are selling it with bricks as an option it absolutely had to be tested both ways.