Will these bricks work for the dome?

[llRobinll]

Hi there,

First off, great forum. The information present here is amazing. I don't think I would even have considered building a pizza oven if it wasn't for this forum, so thanks!

I am currently building a 30" (due to limited space) pizza oven with my father and we just finished the 4" vermiculite isolating layer. We have proper fire bricks for the oven floor and already have the ingredients to make the "homebrew' mortar.

Since we are on a budget we decided to use clay bricks for the dome. We are currently in contact with someone who has 270 yellow bricks left from building a house (they were used for an inside wall) we can get for cheap. According to the seller they are noticeably heavier and harder then the other bricks he has. He also mentioned they are hard to break. I have included some pictures and I'd love to know what you guys think of these bricks, I personally have no expertise in this field and neither does the seller.

Any input or tips are welcome!

Kind regards, Robin

EDIT: sorry, I'm having some difficulty adding the pictures. Working on it...

[llRobinll]

Sorry, forgot to add the pictures...

[Gulf]

Hi Robin,

Welcome to the forum. If any non firebrick will work, my guess is that, those pavers would. I testeds some yellow pavers inside my oven and was impressed by them. Of course, yours are from a different clay source. So, who knows for sure. I would try to get one of the bricks and fire it several times in the coals of a charcoal grill. That will let you know if they are even remotely suitable for the oven.

Good luck on the build.

[llRobinll]

Hi Robin,

Welcome to the forum. If any non firebrick will work, my guess is that, those pavers would. I testeds some yellow pavers inside my oven and was impressed by them. Of course, yours are from a different clay source. So, who knows for sure. I would try to get one of the bricks and fire it several times in the coals of a charcoal grill. That will let you know if they are even remotely suitable for the oven.

Good luck on the build.

Hi Gulf,

Thank you very much for the info. We will try to get a couple of them and throw them in our Weber Chimney fire starter with some coals to see what happens. Anything we should be looking out for in particular?

Also, I am unfamiliar with the term 'pavers' but from your reaction i take it that you think these are made from clay?

thanks again!

[Gulf]

Yes, they appear to me as being made from yellow clay. Probably the same type clay that has long been preferred for firebrick. However, firebrick are fired to a higher temperature than building brick. That has something to do with vitrification. I'll let others address that as it is "above my pay grade".

A lot of streets, here in the US, were once paved with clay brick "pavers". Some are still in use. Those paver bricks were larger and thicker than standard building bricks. A brick paver today is any brick without holes that would make a smooth walking surface for a sidewalk, patio, or floor. They are usually closer to standard bulding brick sizes. They may or may not be made from clay.

Great idea on the Weber chimney. If you can borrow another from a friend, two is even better. Turn the second one upside down and place it on top as a chimney extension to increase the draw. The increased draw will pull more air in at the bottom allowing the coals to start faster and burn hotter. (It is good trick to know for starting charcoal) Also, if you can get some natural lump charcoal, lump will burn even hotter. Get a few coals started and then place the brick in the center of the chimney. Add the coals around the the brick until the chimney is full. Them place the second chimney. You may even add a few more after the second chimney is in place. They will help keep the second chimney stable. When it burns down, use something for a set of tongs and a good glove to pull the brick upward to get some more coals to fall underneath. Then, add a few more coals around it to extend the firing.

I would save one of the brick as a control for comparison later. If the brick have been wet, I would first bake them for a while using indirect heat on the grill. (Introducing a wet brick to direct flame impingement is not what you would do during the curing "drying " process). And, it would not be fair for the test.

What you are looking for is a brick that cracks and falls apart on it's own without being forcefully manipulated. (IE: crumbling in your hands) That is a fail. You want a brick that will not easily degrade and shed pieces continually on to your food..That is what a "concrete" paver would do. Your test should end up somewhat better than that. They may not be as stong as a firebrick or even your control brick, but they may be a good heat bank and last for many years. Firebrick are what we advise. But, there are many folks, oiut of necessity, that build with natural clay as well as clay pavers.

It will be your call after the test. Please let us know how it turns out.

[llRobinll]

Hi Gulf, thanks again for all of the info!
We got some yellow end red clay bricks to test and I included the result in the picture below.

Since we were out of charcoal we decided to built a big fire in the fireplace and put them in the middle of the fire.
We first let them dry a bit next to the fire like you said and them placed them directly into the hottest part of the fire.

We tried theyellow brick first and after half an hour or so we heard a pop and we saw the brick was cracked in two. After taking it out of the fire it fell apart even more... The pieces themselves are still solid and not crumbly but I would think this is a big fail?

We then tried the red clay brick and that one did much better. It got so hot the the brick itself started to glow red. We let the fire die down and after a while I checked the brick and it still looks strong and solid. Unfortunately this brick is of the type with a cavity on one side so we'd have to find another place to get a similar one.

I do think the bricks got unrealistically hot since the heat came from all sides instead of just one. There also still is the possibility that the yellow one still had some moisture trapped inside. We still have one left, so we might let that one dry some more and try again.

[Gulf]

That may very well be a fail for the yellow paver. But, do try to make sure that the second one is dry if you decide to do another test. Good idea looking for a solid red clay brick like the one you tested. If the red clay with the frog turns out to be your best bet, lay them with the frog up. You can fill the indentation with homebrew mortar.

[Gulf]

Robin,

I remember that the subject of using non-firebrick came up a good bit on the UK Wood-Fired Oven Forum. I haven't visited over there in a while. This one keeps me busy enough. cobblerdave and david s were both very active over there. Either may remember some revelations of a few of those builds. Also, a visit over there may be worthwhile to the success of your build. We don't want to loose you over here though!. We just want you get all of the experienced advise that is available. There have been a few folks who have opted for a "home brew " type of castable. That may be another option for you that can be sourced locally for a budget build. Please keep reporting back on what you find and all the steps of your build. We also want to get feed back on how well materials hold up to time and frequency of use.

[david s]

Just by looking at a brick and its appearance can be quite misleading and bear no relationship to its suitability. Similarly hitting a brick with a hammer or throwing into a fire is unlikely to give you an indication of its longevity. It is the materials contained in the clay combined with the degree of vitrification and temperature fired to that determine their suitability. Generally a brick with a high proportion of alumina is better also a low level of iron oxide. Generally red indicates a high level of iron oxide. Higher temperatures the brick has been fired to also better but there are exceptions. A fully vitrified clinker brick fired to 1200 C may suffer from thermal shock while a low fired brick with an open body may perform better. This information is unlikely to be available so although a brick may prove in practice to be quite serviceable it also may not. We used to source creamy house bricks from Cooroy that proved quite suitable for kilns fired to stoneware temperature (1200 C+). A similar looking house brick with a different composition may prove disastrous. Attached are pics of failed solid reds used in a really old fireplaces. The spalling may have taken many years to develop, one firing probably not.