Wet Saw.....2 Thumbs way up!
I rented a wet saw -the Mason Mite II- to cut my firebricks in half. The results were spectacular as I halved 100 in about 90 minutes, including learning to use the saw and refilling the water and discarding used water. After reading how cumbersome and dusty the chop saw was, the $70 seems like an excellent investment. The cuts are amazingly clean, and I cut several odd sizes for possible use as keystones. There was no dust and clean up was a snap. That being said I have a couple questions. First, is it acceptable to set the oven floor in place with refractory mortar? I was told by staff at my materials supplier that fireclay and refractory mortar are the same thing. Second, how long does the floor have to set before construction of the dome can begin? Lastly, how many rings of the dome can one build consecutively without compromising strength and risking collapse? In other words does each ring need to cure or set before moving on to the next? Thanks in advance for your wisdom.
"A little knowledge is a dangerous thing" and ....
(M) I have a paucity of it, so consider other input before acting only on what you read from me:
(WV) I rented a wet saw -the Mason Mite II- to cut my firebricks in half. The results were spectacular <snip> are amazingly clean, and I cut several odd sizes for possible use as keystones. There was no dust and clean up was a snap.
(WV) That being said I have a couple questions. First, is it acceptable to set the oven floor in place with refractory mortar?
(M) No! You want your fire bricks to be able to expand without cracking.
(WV) I was told by staff at my materials supplier that fireclay and refractory mortar are the same thing.
(M) According to what I've read on this forum, "fireclay" is only one of several ingredients in the refractory mortar recommended here previously:
"Begin laying your bricks using refractory mortar (8 parts mortar sand, 3 parts Portland cement, 2 parts fire clay). The bricks will follow the angle and curvature set by the wood shim. After the angle is held in place with mortar, remove the shim; fill the open space created by the shim with mortar, and move on."
(M) NOTE! This mortar is for the dome, and NOT for the floor!
(M) You can find the original plans at
(WV) Second, how long does the floor have to set before construction of the dome can begin?
(M) Immediately since the thin, sand & fireclay layer (NOT the refractory mortar!) has no cement binder in it and doesn't need, or "want" to be set.
(WV) Lastly, how many rings of the dome can one build consecutively without compromising strength and risking collapse?
(M) As long as the dome doesn't fall in, you won't compromise strength. Most builders can complete 6 or 7 chains (courses) before they need support. I didn't use a beach ball or medicine ball but two builders did so and have reported great success that way. I tried balloons which worked OK until they started popping. Most builders used styrofoam vanes, which I also used and which were easily removed after building was completed.
(WV) In other words does each ring need to cure or set before moving on to the next?
(M) Nope; as long as the bricks are supported until the mortar hardens.
(WV) Thanks in advance for your wisdom.
(M) You mean, perhaps, Thanks for nothing.
(M) I'm not trying to toot my own horn since almost all the ovens I've seen are more professionally done than mine. Also, I've made a lot of changes to the standard procedure but if you're curious about one way to build your oven (not necessarily a recommended way, either) go to these two URLs on this Web Site:
You're preaching to the converted on the wet saw - It makes a nasty job simple and clean. A word to those who, like me, are buying the HF cheap wet saw: the $20. when I bought it, and now $30. blade isn't full diamond through the width of the exterior band. It cuts slower and slower, and finally stops cutting entirely, with about a quarter inch of band still on the outside. That said, I did all my geodesic shapes, a bunch of slate, and a bunch of red brick cuts before it gave out.
You can certainly set the floor bricks with refractory mortar: that's how the modular oven floors are put down. It's not the same as fire clay. That sludge in the bottom of your cutting pan on the saw? That's the same as fire clay. It's ground fired refractory clay.
How many rings can you lay up? It depends on how solid your support is underneath. With four vanes you can lay up two at a time. With more, you could go further. There's a limit to how much you can do in a day. As someone said, it's not a chain gang, it's supposed to be fun.
no support needed
As one who used the shim method to find brick angles for the dome I used no internal support except for on the ring I was working on (support for this was just temporary bricks inside the dome to hold up the end bricks in each in progress chain). Once the keystone for each ring is in place the weight of the bricks holds the chain solidly in place - good luck trying to make them move after. The curing of the mortar has little if no impact on strength.
Now, if you use an internal support and the bricks do not have solid contact between each other (because they lean only on the support and not each other) you may have stability problems that the curing of the mortar may help with - you just need to be cautious if you use a support that you compress the bricks against each other.
Using the shim method you could theoretically build the entire dome in one day - but Dmum is right, keep it fun. I do suggest with the shim method you have a helper for the last few rings, otherwise it gets pretty dicey at times.
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