Fireclay bricks or quartz bricks

[Daco]

I'm planing to start to build my firewood oven.
I was at the warehouse and they are convincing me to buy quartz bricks instead of fireclay bricks. What do you guys think?
They told me that fireclay brick have some toxic ingredient inside....

[Gulf]

Daco,

Welcome to the forum. "Quartz brick" is a new one on me. I don't know what toxic ingredient could be in fireclay. Can you ask the warehouse for a link to a MSDS for each of those type of brick?

[UtahBeehiver]

Might be sematics? Agree with Gulf, get a composition of the the two bricks. I looked up quartz bricks and the one I saw had a composition of fire bricks we normally see on this end, ie this case was 42% Alumina Oxide and Iron Oxide. I did see another "clay" fire brick that was composed of 96% silica which could be an issue if this is the type of fire brick they are talking about. It would be helpful to know what the "toxic" element they are talking about. Is there a cost difference?

[Daco]

This is what i found on the internet

	Silica brick	Fireclay brick
CHEMICAL PROPERTIES
SiO2 (%)	95	65
Al 2 O3 (%)	0.7-1.5	23
Fe 2 O3 (%)	1	0.18
CaO (%)	3
Na 2 O+K2O (%)	0.35	0.18
MgO (%)		0.18

[UtahBeehiver]

So which ones are they selling you??

[RandyJ]

I would agree with Utah as to what are they telling you is the bad ingredient? You don't want to be dry cutting any of the bricks as the will all have negative effects on your health. As for normal fire bricks the stuff they are made of is all combined in to the brick and should not be comming out of them.

Randy

[Gulf]

"Silica firebrick" brings up a lot more hits for me. The search for it brings up that it's primary use is in glass firing kilns. I'm sure that there is somebody on this forum that has some experience with it. But, it is above my pay grade. They may be able to tell you how suitable it is, and how difficult it is to cut. However, the "23% Alumina" clay firebrick are. That will work just fine in your oven. Most ovens on this site are built with them. The heat up time, heat retention etc. all work fine in a wood fired oven. That material more closely resembles the clay that humans have been making ovens from for thousands of years. The only difference is that is has been fired to make it last much longer in use. The toxic material that the warehouse is probably referring to is "aluminum". That is not "alumina" in the same form.

My vote: Go with the clay firebrick .

[Daco]

Thanks for the advice. I will stick to the traditional fireclay bricks.
Is the form of the oven important?
I want to use an old cast-iron bathtub for the form, than put fireclay bricks and insulation at the end...

[Tscarborough]

Silica firebrick are insulating firebrick, not suitable for an oven.

[JRPizza]

Daco, yes the form of the oven is important, as if the door height to oven height ratio is wrong the oven won't draw properly, and the shape might have an impact on how efficiently the oven heats (cold spots, circulation). I have seen many designs that seem to work well - round, barrel shape, beaver tail, so you probably can't go wrong copying one of those. If you are going to build an alternate design, I'd suggest understanding the differences between what you want to build and what is proven, and see if those differences matter. You can post them here on the forum and get opinions.
That said, I'm sure we would all like to see what you have planned and will watch your build with great interest.

[Gulf]

Daco,

It is great that you are going with the clay firebrick. (Thanks TScar Tscarborough , your post may have helped me to put two and two to together) I think that MrChiptster mrchipster may have had a bad experience with used silica brick on his first oven. Check this thread out. If you read down a few posts, you will see that I have couple hundred of them that I have had for about 40 years. I did not know what they were, but I knew what they were used for. I will be using them for that same purpose (as an insulator) in my upcoming "bassackards" outdoor fireplace .

I've seen folks build wooden sliding forms for barrell vaults that looked pretty simple to me. Not only is the shape of a cast iron tub not the strongest shape for a barrel vault but, it would be heck to remove.................... You were planning on removing it?