red Vs. fire bricks for the dome

[bickmeier]

I am beginning a bread/cooking oven using a Scott/Rado barrel vault chamber with stepping arches to round off the back and taper the front to establish the flue vent and door.
I have the fire bricks for the floor and would like to use plain red clay bricks for the dome. I see a lot of old ovens with red clay bricks. As long as they fit tightly together, is there a problem with the red clay bricks?

I can buy all of the tapers and wedges I need in red clay for $0.70 a pop, as opposed to $2.00 each for firebrick.

My Brick supplier pushed off Sairset on me, but now I have my doubts. I'm leaning toward an old fashioned lime mortar. Any opinions????

[Tscarborough]

Sairset is fine for the oven lining unless for some reason you are planning on hosing it out or something. As for the "red brick", that is not enough of a description to determine suitability. Is it solid or cored? Extruded or pressed, new or old, sandy or hard fired.

[DrakeRemoray]

Is the oven going to be outside? Sairset I believe is an "Air-Set" mortar which will remain water soluble. Ok for indoor, but not supposed to be used outside.

Scott says you can use red brick for the dome...are you going to be baking bread primarily (since you are not building a pompeii, I assume you are going to be a heavy bread baker). A little spalling might not be a big deal in bread baking that it would be if a bit fell into a pizza...

Really consider your insulation depeding on your usage. If you are going to be baking 50 lbs of bread, then you can probably insulate under the hearth slab, but if you are going for smaller bakes, you will need insulation right under the hearth bricks or you will spend all your money/wood/time firing that thing...

[Tscarborough]

Sairset is actually a HEAT set. The inside of my oven will never even get damp since I keep the door on it.

Red extruded, cored face brick will not work.

[GianniFocaccia]

I errantly built a firepit with Sairset and after the first rain it crumbled likedry oatmeal. Why not go with poor-man's mortar? It's cost-effective and lots of builders have used it with no problems to report.

[dmun]

tapers and wedges I need in red clay for $0.70 a pop

Now this is news. Shaped red brick? Tell us more.

[Tscarborough]

A firepit is exposed to the rain, an oven is not (shouldn't be on the oven itself, anyway). Sairset type refractory cements are very sticky, cheap(er), have a fine aggregate (and thus can make very small joints), and you do not waste any since you do not have to mix a batch.

[DrakeRemoray]

T, I am sure you are right that sairset will work in an oven since it never really gets wet, but it is really not supposed to be used "exposed to the elements". And it is defined as an air-set mortar here and here. Usually the air-set mortars are easier to find as they can be used in all indoor fireplaces. The usual advice here is to use a traditional refractory or home brew mortar that you mix up, not an air-set product. Your mileage may vary...

Drake

[Tscarborough]

Yep, I normally recommend either home brew or heat stop, but the reality is that for an amateur, wet type refractory is often the best choice for an oven (not a firepit or outdoor fireplace).

It is an air SET, but it is a heat CURE. Home brew and Heat Stop are both hydraulic, that is, they will set and cure underwater and do not require exposure to air.

[GianniFocaccia]

Oops... my bad! For the record I did not use Sairset (which appears to come in a bucket and is premixed). I think it was Sairbond and came in a 55lb bag.

Sorry for the erroneous report.