# How much does your firebrick weigh?



## precaud (Feb 20, 2009)

A standard firebrick is 9" x 4.5" x 2.5". Most modern stoves that use firebrick seem to be using "splits" - bricks that are half the thickness (1.25") of standard firebrick. I thought it might be interesting to get an idea of the weight of the bricks used in various stoves. Converting it to lbs per cubic foot (pcf) will help track down same-density replacements if/when they are needed.

So when you have a chance, take a full-size brick out, measure and weigh it if you have a scale that is decent, and report in. If it's a standard "split" (9x4.5x1.25) multiply times 34.13 for the cu. ft. weight.

A full-size brick from my Quad 2100M brick weighs 28.8 oz., which is 61.5 pcf.


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## BrotherBart (Feb 20, 2009)

Standard split brick 3 pounds 8.8 ounces.


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## precaud (Feb 20, 2009)

BB, you must have had one sitting on your desk... by "standard", you mean 2.5" thick?


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## BrotherBart (Feb 20, 2009)

"Standard *split* brick 3 pounds 8.8 ounces."


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## Hogwildz (Feb 20, 2009)

The majority of the brick I seen was 1-1/4" thick.  In stoves, stores etc.
So in my book standard would be the most commonly used.


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## precaud (Feb 20, 2009)

Yeah, but the standard was set before they were used in wood stoves... and standard or 'straights' are 2.5" thick, and 'splits' are 1.25".


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## Jimbob (Feb 20, 2009)

The bricks that come on the P.E. stoves are ~ 2 lb. a piece. 9X4-1/2X1-1/4.
The same-sized heavy ones the stores sell as replacements are ~ 4 lbs.
This is according to some notes I took a few years ago.


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## CrappieKeith (Feb 20, 2009)

Yukon's 9x6x2...9lbs...12x6x2...12 lbs.
3200 degree rated.


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## precaud (Apr 10, 2010)

I just got in some of the "real thing" - 22 bricks of K-30 (2900º) Thermal Ceramics insulating firebrick. It's a nice, rugged brick, not crumbly at all, and should hold up to abuse inside a firebox quite well. A 9x4.5x2.5" brick weighs 3 lbs, for 51 lbs/cu ft density. Thermal conductivity (K) is 0.97 per inch which is excellent. It's a little late in the season to be running experiments, but I look forward to playing with it next fall...


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## begreen (Apr 10, 2010)

My bricks are too hot to measure. Stoves been burning for a week now and will be at least through tomorrow morning.


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## precaud (Apr 10, 2010)

Yeah, you guys are really getting a late-season slam up there.

Your bricks are likely the same as the Quad's, I think PE and Quad both use the pumice bricks.


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## begreen (Apr 10, 2010)

Indeed. After the record Feb and Mar temps my garden is now in freak out mode. Definitely a weird weather pattern this year.  

I'll be interested to read about how the new Thermal Ceramics bricks work out. Were they easy to get? How expensive?


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## precaud (Apr 10, 2010)

Interesting that NOAA's models are calling for warmer and dryer than average conditions up there:
http://www.cpc.ncep.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/page2.gif

They're been pretty right on down here - cooler and wetter than normal.

I got the K-30's at an industrial auction, surplus from one of the local DOE-funded labs. I was bummed that someone else knew what they were and wanted them - I had to pay $40 for the lot. But that's how much the shipping cost would have been had I bought them elsewhere, so no complaints...


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## BrotherBart (Apr 10, 2010)

My bricks in the 30-NC are the two bucks apiece variety and you can have and keep your pumice, thank you very much.  :coolsmirk: 

As to weird weather, been in the nineties for three days and going down into the thirties tonight. What the hell is that all about?


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## begreen (Apr 10, 2010)

precaud said:
			
		

> Interesting that NOAA's models are calling for warmer and dryer than average conditions up there:
> 
> They're been pretty right on down here - cooler and wetter than normal.
> 
> I got the K-30's at an industrial auction, surplus from one of the local DOE-funded labs. I was bummed that someone else knew what they were and wanted them - I had to pay $40 for the lot. But that's how much the shipping cost would have been had I bought them elsewhere, so no complaints...



Yeah, NOAA suckered me in with that prediction. I planted several items out of the greenhouse into the main beds during March. Needless to say, they are not happy. 

Nice deal on the bricks. That's less than $2 each. Let us know how they work out.


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## precaud (Apr 10, 2010)

> you can have and keep your pumice, thank you very much.  cool smirk


Well I'll take the other side of that one. I think the pumice bricks are hard to beat, really. Excellent specs, cost effective, and durable enough as long as you don't abuse them. At the end of season 3 with the Quad, the bricks look no different than they did on day one. Being so close in density and K-factor, I don't think the K-30 bricks will make any improvement over them so I probably won't waste my time on that exercise. The material I'm most interested in comparing the K30 to is the Skamolite, which is used in the X33. While it's a definite improvement over metallic liners, I'm not convinced the Skamol is the best material overall. We'll see.



> Yeah, NOAA suckered me in with that prediction. I planted several items out of the greenhouse into the main beds during March. Needless to say, they are not happy.


Ouch. I hope they survive. That arctic jet stream has been really persistent this year. Let's hope it breaks soon!


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## Battenkiller (Apr 10, 2010)

precaud said:
			
		

> I just got in some of the "real thing" - 22 bricks of K-30 (2900º) Thermal Ceramics insulating firebrick. It's a nice, rugged brick, not crumbly at all, and should hold up to abuse inside a firebox quite well. A 9x4.5x2.5" brick weighs 3 lbs, for 51 lbs/cu ft density. Thermal conductivity (K) is 0.97 per inch which is excellent. It's a little late in the season to be running experiments, but I look forward to playing with it next fall...



Sounds like pretty good stuff.  I have a couple of cases of IFB in my basement (no name on box, Chinese in origin I'll bet).  I just grabbed one and tossed it on the scale.  3 lbs, 7 oz.  They appear to be a nominal size (about 1/8" short in each dimension) 9" x 4.5" x 2.5" brick.  Not sure what the thermal conductivity is, but I purchased it from a company that makes pottery kilns, so it must spec out OK for that application.  They were quite cheap IIRC.  It is not as porous looking as the stuff in my wife's hot glass kiln, but I can't get one of them out to weigh since they are cemented in place.  I also have a small laboratory kiln that goes up to 2500ºF.  Gut feeling is that the brick in both of these units is less dense than the loose brick I have.

I have lots of hard firebrick "splits".  They weigh just a hair under 4 lbs. each, so are a bit denser than the stuff BB pulled out of his stove.  I also have a few bricks of an extremely light refractory material that came from a jewelry repair supply house.  They are 6" x 3" x 1.5" and weigh 5 oz, so density is only 20 lbs/cu ft.  They can withstand an oxy-acetylene jeweler's torch (>5000ºF) all day without getting hot on the other side, but the extreme temperature makes short work of the material.

I'm curious to know at what temperature your brick has a K value of 0.97/in.  Most IFB only has a K that low at temps around 500ºF.  Thermal Ceramics doesn't have specs for K-30 IFB on their website.  With most brick, the lower the K value, the less heat it can withstand without damage, or at least that's a trend I've noticed from various spec sheets.


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## precaud (Apr 10, 2010)

Battenkiller said:
			
		

> I'm curious to know at what temperature your brick has a K value of 0.97/in.   Most IFB only has a K that low at temps around 500ºF.  Thermal Ceramics doesn't have specs for K-30 IFB on their website.



You're right, it appears they don't offer a K-30 brick anymore except in Spain. My data are from a PDF sent to me last year by an eBay vendor that was selling some mil surplus K26 and K30 Thermal Ceramics bricks. The only K-values given are at 1000F; 0.389 for the K-30, so .389 x 2.5" = .97/inch . And yes, graphs of K vs temp for all IFB's appear to slope upward from left to right; i.e. they lose insulating value at higher temps, though still far superior to other viable alternatives. Not sure that's a bad thing for stove use, though.



> With most brick, the lower the K value, the less heat it can withstand without damage, or at least that's a trend I've noticed from various spec sheets.



Yes, I think you've identified the tradeoff. The lower-temp IFB's are more porous, and therefor insulate better, but they break down easier. That's why, last year when I was looking into this stuff, it looked to me like the K-28 or K-30 brick would perhaps be the sweet spot for woodstove use; porous enough to insulate well, but with higher density and crush strength to withstand some abuse.

It sounds like your Chinese IFB would be a K-32 equivalent or thereabouts. Should be fine for woodstove use.


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## precaud (Apr 10, 2010)

Here are some specs for what TCI now calls their JM-30 brick, it is rated 3000F, 65 lb. density, K at 1000F = 0.418 which is 1.05/inch:
http://www.matweb.com/search/datasheet.aspx?matguid=df32b3d5d2944b38995373cf26b9ae7d

Crush strength is 439 psi vs 275 for the K-30, so this stuff would hold up even better to abuse.


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## begreen (Apr 10, 2010)

I don't know much about these bricks. The discussion makes me wonder if anyone has made a 2 layer brick that combines a tough, high density surface on one side, with a more porous insulation surface on the other side?


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## precaud (Apr 10, 2010)

BG, I'm not aware of any such. It sounds expensive. I guess it should be said, that's the basic idea behind Jotul's cast iron/ceramic wool sandwich. If the iron didn't weigh so darned much, it would work alot better...


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## Battenkiller (Apr 10, 2010)

precaud said:
			
		

> BG, I'm not aware of any such. It sounds expensive. I guess it should be said, that's the basic idea behind Jotul's cast iron/ceramic wool sandwich. If the iron didn't weigh so darned much, it would work alot better...



Given the price of a new Jotul, they should give you a titanium/Kaowool sandwich. :roll:


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## precaud (Apr 11, 2010)

That's no kiddin'...


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