Do I have to use Fireclay in my mortar for the dome?

[saviomf]

Hi all, I am building a barrel oven, and following some builds from this forum and others. Everything's going great, except one issue: I can't source fireclay cheaply. Do I need it in my refractory mortar? I am planning to use lime, sand and cement, will that suffice? What exactly are the benefits of fireclay? Isn't the lime which binds it together? Cheers.

P.S Love this forum

[dakzaag]

You need some clay, it takes the heat. Try a pottery supply, they will not likely recognize "fire" clay, but they will have a lot of clay. Personally, I believe just about any clay would work, but ask the supply house and they will be able to make a recommendation. Remember that the oven will not reach temps much over 1500 F which is quite low for pottery firing so the clay should have a low vitrify (bisque?) temp. Most fireclay is actually just dust from the making of firebrick. If you made all your cuts first with a wet saw, you would have all the fireclay you need just by saving the gummy slime at the bottom of the saw pan. I cannot say what kind of clay will work the best, but I have seen some grey and yellowish clay that acts and looks like fireclay.

[david s]

Yes, any clay should suffice, but avoid bentonite as it has extremely small particles which leads to greater shrinkage which can cause problems. The cheapest source of clay I can find is Bricklayers clay. If you have to get some through a pottery supplies place the cheapest and most suitable should be ball clay. Don't get clay in a plastic state, what you want is powdered clay.

[jonv]

When you say you can't source it cheaply, how much did you find it for?

How much do you need - I found several places where it was reasonable, but some have minimum order requirements?