I've finally started our oven in Costa Rica

[dmun]

Re: I've finally started our oven in Costa Rica

Tapered firebricks are a refractory supply item. They form the doorways and tops of kilns and furnaces in a number of applications. They come in various duty ratings and are quite expensive compared to the low duty rectangular bricks you get at the brickyard.

If you live in a big place, there is probably an ANH (Harbison-Walker) branch nearby, or a pottery kiln supplier should be able to order them (Just don't get the insulating kind)

[sjmeff]

Re: I've finally started our oven in Costa Rica

Carlos - thanks for the detailed response. This is very helpful. I don't believe that tapered bricks are available around here though I will check. Either way, I think I'll try to do this as you described (drawing the arch and then laying out the bricks on the ground). If I can get it to work that way, I'll attempt the second, outer arch.

I will let you know how it goes! Thanks again.

Cheers,
Stephen

p.s. Last year I was at Earth University in Lim?n for a week for work. Absolutely wonderful staff and students. Very inspiring. I can't wait to get back to Costa Rica.

[carloswlkr]

Re: I've finally started our oven in Costa Rica

the circular arch landing with the tapered bricks looks really nice. I wanted to ask what technique you used for this.

Stephen, Thanks for the kind words. I have enjoyed building it immensely.

My arch was very easy, thanks in no small part to the ready availability of tapered firebricks. I started off by deciding the width and height I wanted for the inner arch, then I drew the arch on the floor using a compass (actually, the compass was at the brick foundry; at home I used a string and a piece of chalk). Next, I started lining the bricks along the half-circle to see which ones pieced together best. If you don't have access to tapered bricks, you could easily use the same technique with rectangular bricks to determine the size of shimmy you would need to use to get a uniform arch and gap between each brick.

My inner arch was made with bricks cut in half, stacked with the cut side towards the inside of the oven. I used the flat part of a long level to make sure the face of the bricks were in line as I went up. I think I only set down 4 or 5 courses the first day, and the remainder on a subsequent day. I cut a support out of two pieces of plywood, using the same radius of the circle that I had measured for the arch. With the support in place, setting the rest of the bricks on the first arch was quick work.

To determine the outer arch, I added an inch (or was it an inch and a half?) to the radius of the circle, and drew another half circle on the floor. I laid out the bricks again along the new arch, to see which ones fit best together. I ended up using a combination of #22 tapers (same as I used in the construction of my dome) and the regular #1 standard firebrick (these are local foundry brick size numbers -- since I'm a newbie, I have no idea if these numbers are standardized). The outer arch is 1 1/2 bricks in depth (13 1/2" total), and for stability, I offset cut and full-length bricks as I built the first several layers up until the vent, at which point, I continued the outer arch with a standard length brick and another plywood support system.

The inner and outer arches lined up easily, and are connected with a very thin layer of mortar. Both arches have a standard 2 1/2 " thick rectangular brick laid on its side to add a bit of height, and the half-circle starts from that height.

Does this help at all? Again, I think mine was quite easy to do, since all the bricks were laid square (or if you don't have tapered bricks, you would still line them up square along the inner edge). I like the clean look, and didn't have to calculate very much to achieve it. But there are some great looking opening arches on the forum with a wider opening, tapering in to a more narrow inner arch, and I take my hat off to those who were able to tackle those beasts!

Good luck!

[sjmeff]

Re: I've finally started our oven in Costa Rica

Carlos - I'm really enjoying watching your build. As others have commented, the circular arch landing with the tapered bricks looks really nice. I wanted to ask what technique you used for this. I feel like I could probably forge my way through the first arch, but when it came time for the outer one (leaving a lip for the door), it would be difficult to get the two to line up well.

Thanks,
Stephen

[carloswlkr]

Re: I've finally started our oven in Costa Rica

I did two more fires on Friday and Saturday to get the oven to temperature for last night's Oscars party. I may have been over zealous on friday, reaching pretty high temps. The oven cracked a bit more, and you could see the moisture escaping from the cracks. But they are all along mortar joints, and none is very visible from inside, so I'm not worried.

I had my first test pizzas on Saturday as we were cleaning up the mess and readying the ranchito for Sunday. The dough wasn't my best, but the oven worked like a charm. I bought new tools (had a rake and shovel made, and found a brush that will work), and tested them out, too.

Last night was my baptism by fire. We had a group of friends over, and made 16 pizzas. It was a great night, and everyone brought something to contribute. We had some creative pizzas, like a white pizza (no sauce) with caramelized onions, fresh mozzarella, goat cheese, and mushrooms; several with shrimp; a pair with anchovies; and an assortment with varying combinations of roasted peppers, marinated eggplant, feta cheese, prosciutto, arrugula, kalamata olives... and the last two were sweet pizzas with chocolate fudge sauce and fresh strawberries.

It was a great night, and the oven was a joy to work. Now I'm off to Honduras for another week, but when I return, I'll get to work insulating and finishing the odds and ends.

Meanwhile, here are a few shots of the oven, party and pizzas.

Thanks again for all the advice and feedback over the last few weeks!

[Les]

Re: I've finally started our oven in Costa Rica

Carlos,

I think you have the record for the smallest crack - you did good. I would bring it up to plasma (in due time) and keep an eye on it. If it gets 4 times larger, then throw the blanket on it and call it good. You have no worries!

Les...

[Dutchoven]

Re: I've finally started our oven in Costa Rica

carlos
speaking now from experience...cracks are going to happen...they suck when they happen but they happen no matter what...I believe everyone's ovens have cracks...just some of the cracks can't be seen...James told me when my oven cracked that the cracks that appear in the beginning don't usually seem to move again....all looks normal to me
Best
Dutch

[carloswlkr]

Re: I've finally started our oven in Costa Rica

I got home from the beach last night to find the two design styles. My wife chose one, and again changed her mind about round vs square, so we'll be going with round pipe. It's a somewhat odd looking transition from the opening vent (a 4 1/2" x 10" rectangle) to the 8" round pipe, but I think it'll look good once it's installed. I burned another curing fire last night with the mock-up attached, and it seemed to help the draw even more.

Again, I'm away from my build for 5 days, but I took plenty of pictures and video of last night's burn, so I'll have clips to keep myself company. Meanwhile, here are a few pictures of the curing fires and the make-shift shelter I've erected to keep the oven dry in case it rains in my absence.

Pictured also are the small hairline cracks that have appeared after the firings to date. The one in the opening arch is in a mortar joint, and follows the joint until it juts up against a brick. The outer crack seems to be in the layer of refractory mortar that I used to smooth over the oven, but I couldn't find a corresponding crack on the inside of the dome.

[carloswlkr]

Re: I've finally started our oven in Costa Rica

Thanks, all. Not sure which I'll go with... The chimney supplier did a mock up of two designs for the transition from the oven to the pipe I had asked for, and left them at the house yesterday. We should arrive home from the beach tonight and take a decision. Hoping all went well with the second fire, but I haven't looked inside since after fire #1 on Thursday morning. Crossing my fingers here...

[dmun]

Re: I've finally started our oven in Costa Rica

American flue liners are square (or rectangular) with rounded corners, European ones, as well as the manufactured chimney systems are round. Both seem to work fine.

[glennb]

Re: I've finally started our oven in Costa Rica

Hi Carlos,
I'm a fan of the round chimney to suit the igloo shape, but it's entirely up to you.

Looks like we'll both be cooking our first pizzas very soon (maybe next weekend).

[Dutchoven]

Re: I've finally started our oven in Costa Rica

any thoughts on square vs round chimney pipe?

In my opinion it is entirely up to you...I don't think it will make much difference in the oven's performance...great job on the oven
Best
Dutch

[carloswlkr]

Re: I've finally started our oven in Costa Rica

any thoughts on square vs round chimney pipe?

[carloswlkr]

Re: I've finally started our oven in Costa Rica

Thanks George. Curing is going well. I kept a fire going for about 2 hours last night, hovering around 350. It did flash up to 450 a couple of times when the flames got high, but I think all in all it was OK. I left a medium size piece of wood on the coals and closed the entrance with fire bricks before I went to bed. I haven't insulated yet, so last night, the outside of the dome started getting warm...

We're off to the beach this weekend, so I won't see the oven again until Sunday night. I can already feel separation anxiety setting in...

[gjbingham]

Re: I've finally started our oven in Costa Rica

I love your oven. Really nice! Let us know how the curing is going.
G.