Recycled kiln bricks and possible water based mortar residue...

[Lburou]

We're cutting dome bricks and need some reassurance concerning the potential downside of a thin residue of old mortar remaining after recycling the firebricks. We don't want any surprises.

I've just rubbed the brick sides together to clean it off (1/32 to 3/32 inch crust & a slow process). I'm concerned that the original mortar used for the kiln, 50 years ago, could be vulnerable to water damage, but don't know how to determine that (does anybody here know?).

I've cut maybe 70 bricks and on two or three of them, soaking in water loosened the mortar layer enough to scrape it off with a putty knife. Most residue is unaffected after soaking for cutting.

I plan to have a permanent cover over the oven, eventually. I'm using the home brew mortar for the oven construction. I can keep it pretty dry during construction, and until curing is complete. If there is an issue, I could cure it before insulating it.

Any thoughts are welcome.

Thanks for your input.

[Tscarborough]

Re: Recycled kiln bricks and possible water based mortar residue...

Just build the thing.

[david s]

Re: Recycled kiln bricks and possible water based mortar residue...

Check to make sure they're the right bricks. You need dense firebricks not insulating firebricks. If you pick one up it should be heavy.

[Lburou]

Re: Recycled kiln bricks and possible water based mortar residue...

Check to make sure they're the right bricks. You need dense firebricks not insulating firebricks. If you pick one up it should be heavy.

Thanks David, there is no doubt, they are medium duty fire bricks

Its easy to change a thing like mortar residue at this point, just wanted some reassurance there was no blind side coming

I appreciate your helpful response.

[Johnny the oven man]

Re: Recycled kiln bricks and possible water based mortar residue...

I'm always hesitant to advise on using 2nd hand firebricks.
Do you really know what sort of environment they have been working in?
Could have some REAL nasties in them. Have they been used in a pottery application where glazes have been used. How about a nasty metals, or even worse a cremator of some sorts!!!! Could have come from a chimney stack emmitting flourides.
Just not worth the hassle unless you are 100% sure.

[Lburou]

Re: Recycled kiln bricks and possible water based mortar residue...

I'm always hesitant to advise on using 2nd hand firebricks.
Do you really know what sort of environment they have been working in?
Could have some REAL nasties in them. Have they been used in a pottery application where glazes have been used. How about a nasty metals, or even worse a cremator of some sorts!!!! Could have come from a chimney stack emmitting flourides.
Just not worth the hassle unless you are 100% sure.

Thanks for your thoughts

The bricks on my house were baked in the kilns that were torn down. No nasties or glazes or bone fragments to worry about. Was just concerned about the residue of the original mortar, and I guess nobody has any advice, save to go ahead and build the oven

[Pdiff]

Re: Recycled kiln bricks and possible water based mortar residue...

My oven is built from recycled kiln bricks (lumber kilns). On the dome, I used 1/2 bricks, putting the cut face in. I started out trying to clean like you, but eventually just started using them as they were. Occasionally I had to scrape a bit to get a good fit, but had no problems. The dome was uncovered (under tarp) for about a year before I could get a housing built around it. I had no problems other than the usual cracking in the overlaying mortar. I doubt it was due to old residue. I did take the advice of others here and used new brick on the floor. It made a tighter fit and smoother surface as many of the used bricks had worn edges that would have left big gaps.

Pdiff

[nissanneill]

Re: Recycled kiln bricks and possible water based mortar residue...

Lburou
go ahead with your build.
My oven s documented well, was built with recycled firebricks from our demolished abbertoirs where they were used in the steam boilers. I picked them over and collected them myself from the site so I knew their history.
I also used the home brew with fabulous results, 2 mixes on succeeding days and the dome was done with the floor cut to fit between mixes!

Good luck and happy building

Neill

[Lburou]

Re: Recycled kiln bricks and possible water based mortar residue...

My oven is built from recycled kiln bricks (lumber kilns). On the dome, I used 1/2 bricks, putting the cut face in. I started out trying to clean like you, but eventually just started using them as they were. Occasionally I had to scrape a bit to get a good fit, but had no problems. The dome was uncovered (under tarp) for about a year before I could get a housing built around it. I had no problems other than the usual cracking in the overlaying mortar. I doubt it was due to old residue. I did take the advice of others here and used new brick on the floor. It made a tighter fit and smoother surface as many of the used bricks had worn edges that would have left big gaps.

Pdiff

Lburou
go ahead with your build.
My oven s documented well, was built with recycled firebricks from our demolished abbertoirs where they were used in the steam boilers. I picked them over and collected them myself from the site so I knew their history.
I also used the home brew with fabulous results, 2 mixes on succeeding days and the dome was done with the floor cut to fit between mixes!

Good luck and happy building

Neill

Thanks for the encouragement!

We are passed the concern for the unknown mortar residue. Of all the 200+ bricks cut so far, only those first few bricks showed the crumbling residue after soaking. No longer a concern. Glad to hear others have had good luck with recycled bricks.

We have a half brick soldier course, nine chains, and inner arch completed (always with a cut face in). I'll be closing the dome as soon as I can get around to it.

Using the home brew, with calcium aluminate option. Some surface cracking due to the accelerated curing of the mortar. No big deal expected there.

Thanks again for the encouragement!