Oatmeal on the Dome

With winter rains approaching as fast as the new year, it was time to get back to building. Waterproofing the dome is the next task that I need to complete. My plan was is as follows: wire mesh over the insulation, to be covered with vermiculite concrete. On top of the vermiculite concrete, I planned to apply a hard, water resistant, stucco shell colored to match teh existing stucco walls.

From the Baker's Notebook

I keep a plain, black sketchbook in the kitchen and use it as a notebook to prepare and record each days bread dough formula, temperature calculation, and kind of flour used, etc.

My goal for yesterday was to make enough dough for about 12 pizzas. Because I do a hand mix, I've been needing to add a lot of flour once the bread hits the bench, so I decided to try a lower-than-usual hydration of 72.5%.

Here are my notes transcribed from my notebook:

Rain, Rain, Go Away (by Sunday)

Early Wednesday morning I picked up some anchors and a masonry drill bit from the hardware store and drilled, sealed and bolted the flue base back into place. The tarp went back on the oven dome to await the rain, which arrived late Thursday night.

If the rain eases on Sunday afternoon, I plan to have the oven up and running for a pizza party. Otherwise, if the rain persists into Sunday night, pizza next week!

Regardless, dough will be made Sunday AM and put into the fridge. This week's dough will be with the fine Caputo #00 flour, as (once again) no Giusto's at Surfa's!

Oops.

Because rain was forecast for Monday, and because I haven't had time to water-proof the dome, I decided to throw a tarp over the oven. In the past, I have removed the flue pipe, and placed it inside the oven, so that the tarp fits snugly.

On Saturday, when I tried to unscrew the flue pipe, I pulled the metal plate that attaches to to the oven arch off with it. Seems like just cementing this in place with refractory cement is not enough. I guess I'll be picking up a few masonry anchors this week, and looks like I''l be drilling, holes in the bricks and res-seating the base plate with some furnace cement on Saturday -- weather permitting -- as more rain is forecast.

Cold Front

Approaching weather (yes L.A. has weather) is pushing our now-customary Sunday night bake ahead one night to Saturday. It's 60° in the backyard now, and it will probably drop into the 50s by the time I am ready to bake, so the plan is to go for a big, hot fire that will bake pizza and keep us warm.



Today's dough recipe (by weight) was as follows after the jump:

No Sticks and a Plan

The bake on Tuesday went pretty well. 10 pizzas, no problems with the red sauce ones breaking up or sticking. I got a late start firing the oven (LA traffic), and so I rushed that a bit with no major consequence except the heat on the floor was a little low for the last few pizzas.

Had some pears, so I capped off the night with a gorganzola, pear & leak pizza. Fantastic.

Cold Oven

Sadly, no pizza on Sunday.

Instead, pizza bake will be happening tonight!

Just mixed up 5 lbs. of dough. Giving it an hour to ferment, then a fold, another rest, then pre-shape, divide, shape, and into the retarder until 2 or 3 this afternoon.

I have the oven door all laid out, but not cut. I was hoping to build it today so I could bake bread for Thanksgiving, but sadly it may not happen. My plan is to make the door by sandwiching 2" of 2600° insulation between a piece of sheet metal (for the interior side), and a piece of plywood. If that design works, I'll upgrade the plywood to solid oak.

Pizza Pictures

Just a couple of pictures from last night. We made 11 pizzas in about 2 hours; could have made more if we had more dough.

I started the fire with three pieces of almond wood at around 3:00 in the afternoon. This has quickly become routine for me, so even though the oven was completely cold (60 degrees) I wasn't worried about having it hot by 4:30.

Pizza Encore

We had so much stuff left over from Friday night, that we decided to do another pizza night on Sunday. I had to make up a new batch of dough and prepare a couple of gluten-free crusts for some of our guests.

I was pretty much out of the (pricey) Caputo 00 flour and the only bread flour I could find in the neighborhood market was Gold Medal.

Pizza!

I spent Friday morning picking up last minute supplies: Surfas for a new metal peel, and a wire brush/scraper combo thingy; cheese, toppings, and firewood from the grocery store; Baller's for a dowel and hardware to extend the handle on my old wooden peel.

At around 1 PM, I mixed dough, then went back out to work on the peels and brush.

Final Test Firing

With a real pizza bake planned for tomorrow night, this was the last opportunity to test-fire the oven.Today's target: carbon burn-off on the entire dome. Supposedly, at around 700° the black carbon that builds up on the oven walls is supposed to turn white (clear). Once the whole oven turns white, you can bank the fire and start cooking pizza.

The oven was still at around 100° from yesterdays burn. I'd stacked my last 3 pieces of almond wood in the oven overnight to kiln dry. At around 11:15, I started the firing with kindling and 2 sticks of almond wood and a piece of 2x4 right in the center of the floor. It started out great, so i decided to throw the third log on, and almost immediately knocked the fire out (yay me!).

I rebuilt it with more kindling and a few pieces of scrap birch. It was quickly licking the roof of the oven.As the oven heated up, the fire changed from something akin to a standard fireplace to a fuel burn of turbulent flames rolling over the surface of the oven dome.

At around 11:45 I saw the first sign of "whitening" of the carbon that had built up on the oven ceiling. By 11:15, the entire oven except a couple spots near the opening had cleared! I was so happy, relieved, excited, whatever! The oven works! It really works!

I spot checked the walls and ceiling at 11:30; 750°+ on the walls, 800°+ at the apex of the dome, and 650° on the hearth! Amazingly, the outside oven temperature still at around 70°F! I banked the fire to the side and watched as tendrils of steam worked their way out of the insulation -- hopefully, that's the last of the water.

Tomorrow we bake!

Day 12: Insulation

I'm now planning to keep the igloo shape, and because I didn't want to mess around with the vermiculite cement stuff, I decided to insulate with Cerablanket.



It's fairly easy to work with. 50 SqFt easily covered my 45" diameter dome. The blanket is held in place with a few galvanized wire straps anchored with concrete screws. The blanket really changes the shape of the oven. During the test firing yesterday the inside temperature at the back wall was around 500° right where the fire was, the outside temperature at the same location was 81°.

Next is to figure out how to encapsulate the oven and its insulation in a waterproof jacket. I have three ideas in mind:

• Stucco; easiest to install, but perhaps the least interesting look-wise. I suppose I could cover the stucco with tile, brick, or...
• Metal; this appeals to me as it would keep things going in the "steampunk" direction style-wise. I'm looking at both steel and copper as possible materials. Copper is appealing because I have the tools to work it. Steel -- rusty with big rivets and metal bands -- really appeals to me aesthetically, but is clearly a lot more work and I think I would need help forming the pieces.
• An Andy Goldsworthy-style stone "pinecone."

Later Firings

I've been slowly building up the temperature with successive firings. I got it up to 350° average wall temperature in about an hour today. Hoping to have it at pizza-making temperature by Friday!

Books & Machines

Back in September I took an oven & pizza building class at Machine Project taught by sculptor Michael O'Malley. He recommended these two books:

They are both fantastic. I especially enjoyed the Hamelman book, Bread, because it explains how bread works. Michael was also using this interesting mixer:

It's called the Assistent made by Electrolux, Sweden. It's asymmetrical, space saving compared to a Hobart standing mixer, and has a built in timer instead of an on & off switch.

On the second day, the class built a temporary pizza oven on Alvarado Blvd. Video here, link to more photos here.

First Firings

Everything was really wet after the storm so I let everything dry out for a week then did a test burn of a couple wads of newspaper and a chunk of 2x4. Smoke started leaking out of some hairline cracks around the bricks at the top of the dome. After things cooled down I pushed additional mortar into these joints with a grout float. Two days later I fired it again with a slightly larger pile of stove wood (a half dozen pieces) no smoke out of the dome! However, a lot of smoke out the oven door. It seems my flue opening is much to small! I may need to rebuild it, or cut out some material with a grinder sometime in the future.

You can see how small the opening is in the picture. Smoke skirts the edges of the opening and swirls out the front, especially if the wind changes direction to blow from behind the oven.

Day 11: Mud All Over

Two days later, and new bucket of mud has been applied over the whole thing. The flue has arrived and been fitted too! (Looks a it like a steam engine to me.)

Anyway, everything is done just in time as I am going on a 1 week camping trip and a typhoon is coming in a couple days.

When I get back from the trip, my work vacation is over, too.

Day 10: Arch and Flue

The flue opening is the least well documented part of the Forno Bravo plans. I found some proportions of 2:1 of flue to flue opening and followed that. [later I would realize that my flue opening is much to small!]

The flue opening was formed by cutting out segments of the brick arch over the oven vent/landing. I decided on a metal flue, and mounted the flue pipe base directly on top of the flattened top of the flue opening. I spent the rest of the day covering as much of the dome exterior with mortar and filling large gaps with bits of brick. I got about a third of the dome covered before I had used up bucket number two of refractory mortar.

Day 9: More Courses; More Troubles

I started on more courses a day or two later. Everything was going pretty smoothly -- I thought! -- until I noticed that the open ends of the vault were sagging inwards. Luckily the refractory mortar was still plastic and some wedges and props got everything pretty much back in line (or circle). I had to add some squinches to make everything fit correctly.
Messy but virtually invisible -- as this area will be right inside the oven door. I was ready to do my first completely closed ring. It came out slightly eye-shaped, but no worries: I figured I could fix it on the next course. I was now on the last few courses, and the angle of the bricks meant that I needed some more supportive forms.

I also built the side walls of the oven landing/flue arch so that they would have plenty of time to cure hoping to thus avoiding the thrust issue I encountered with the oven opening.

I cut a plywood circle with the jigsaw and marked a bunch of concentric circles for guides. This was propped up in the center of the vault with a scrap of 2x. Wedges laid on the plywood supported the bricks at the correct height.

At this point I fixed the out of roundness issue with two more squinches. (covered with mortar on the right of this image.) A few rings closed the top. I immediately popped out the form and cleaned up the mortar on the inside of the dome. Dome done!

Day 8: Arch Troubles!

It was time to spring the arch for the oven door. I quickly made a ply wood template and cut and laid in the arch bricks. Everything fit perfectly. I pulled the arch support and then trouble struck: the mortar on the piers supporting the oven door arch had not set enough and the thrust from the new arch started spreading the thrust blocks.

Some clamps quickly stopped the movement. At this point I also realized that the new arch could not adequately absorb the forces from the incomplete oven dome rings. More clamps, and some bricks for counterweights helped get me back on track. At the end of the day, I had the oven opening and 4 courses.

I love the look of the oven at this point with the clean interior and the bristle-block exterior. I wish it could stay this way!

Day 7: Helpers!

With the base and floor done, I figured things would go pretty quickly from here. I convinced a couple of friends to come over and help.

I cut two quarter circles of plywood to the diameter of the finished oven dome and used these to true the floor and the dome vault. The great thing about these forms were that they would fit out the oven door so I could use them for all the courses, and they could be positioned wherever I needed them.

Generally this meant at the start of a course and under the brick I was working on. I also used them to check that the arc of the vault was staying true and to make corrections as needed.


With one person cutting bricks and me placing them it did go pretty quickly too a point -- but it ended up taking three times longer than I thought. [9-year-olds can help cut bricks, too!]
I had fabricated wood wedges to the correct angle needed between bricks. I used these a lot on the later courses, but the early courses went together without incident. Once the angle was set correctly on a few bricks in a ring, it was easy to "feel" the right angle on the remaining bricks in that ring.

Day 6: Oven Floor

I cut the ceramic insulating board into the appropriate shapes using a jigsaw. The pieces were glued down with coupe dabs of liquid nails. [Note: Ceramic insulation is nasty stuff and needs to be treated as a hazardous material -- respirator, eye protection, gloves, etc.]

The insulation material loves to soak up water. Before setting the floor bricks in their fireclay-and-sand base, I had to liberally wet the board with water. I had to work quickly with the fireclay mixture as the board soaked the moisture out of it in seconds.

I wasn't too worried about the bricks overhanging a bit as I was planning to cover the entire oven in an oven enclosure. [This later changed, requiring some remedial cutting with a masonry saw on an angle grinder!]

Day 5: Dry Layout

The next day I did a couple of dry layouts to get the dimensions and oven location on top of the slab worked out. I took a lot of photos for future reference. There were two things I needed to work out: The general location of the oven, and the size of the oven floor.

Because of some site limitations, I had planned to place the oven dome back as far as possible on the slab. I wasn't sure how much space I would have for the oven landing. A couple of layouts got me the info I needed.

I had decided to go with the ceramic insulation board for insulating the oven floor, so I measured for that and ordered it from a local oven supply. I also did a couple of layouts with different herring bone patterns for the floor -- I wanted to make sure that the front line of bricks wasn't going to have a lot of awkward cuts.

The final dry layouts were marked in the slab with chalk. Nothing to do now but wait for the slab to dry a bit more.

Day 4: Slab & Block Fill

Day four was a quick, 3-hour work day. Concrete was mixed and poured into the block voids and slab form. At this point had hadn't decided if I should go with ceramic board or vermiculite concrete for the insulating layer. The surface was left rough for application of another layer if needed. The finished slab is 56" square and about 4" thick over the block and 3.5" over the span.. The target is to get the oven floor to 40" above the patio; the existing block base is 32 inches, the slab adds 4 inches, the insulation layer will be 1.5 inches thick and the bricks are 2.5 inches thick. That adds up to 40 inches -- right on target!

I eased all of the edges of the slab -- this isn't really necessary, as this is going to be covered with other materials eventually -- but it's a very satisfying task.

Day 3: Rebar and Formwork

I placed more rebar and mesh. Two #4's in the bottom of the lintel, and #4's at the top pf each wall and in every other core. More #10x8" mesh; this time as bottom reinforcement for the 3.5" slab. The bar across the front opening was bent so it will be one continuous piece for some lateral support.

The 2x6 forms for the foundation slab were modified to make new slab forms.I used some load tie downs to secure the 2x6's and placed scrap pieces at the midpoint of each 2x6 to keep the forms from bowing.

I cut and beveled plywood to support the middle of the slab while it's being placed. The plywood form that covers the middle part is in two pieces that can fit out the "door" once all the concrete sets. All the wood is wedged into place to allow for easy removal and the plywood is covered with plastic to keep it from sticking to the concrete.

Day 2: Laying Block

After letting the slab cure for three days, it was time to lay block. Unfortunately, I chose the hottest day of the year: 106+F! I had a hard time keeping everything wet and workable.
I also miscalculated my block needs and had to run out and buy 9 more blocks! Anyway here is the finished block base.

Day One: Excavation and Slab

First step is to dig out the space for the supporting the slab. The slab is framed from 2x6 so the slab will be 5.5 inches deep. The excavation is about 7" deep. The last inch or so was into sandstone bedrock. I filled the excavation with 1.5 inches of sand, leveled it, placed a vapor barrier, put a little sand on top to keep it in place and then set in the forms.

The slab will be 60" square and be reinforced on the bottom with 2, #4 rebars running underneath where the block walls will eventually go, and #10x8" wire mesh on top.




Here is the slab placed and finished at the end of Day 1. those are #4 dowels placed in what will be every-other block cell (16" o.c.). The slab is broom finished where the block will go and steel troweled smooth in the center, which will remain exposed.

Oh, and pulling out the old fence post was a bear!

Day Zero: Choices

Before I can start I have to make two choices: What kind of oven, and where should it be.

The first choice was pretty simple: I decided to go with a design based on the free Forno Bravo "Pompeii Oven" plans. The plans can be downloaded for free from the Forno Bravo website. The plans have been used by hundreds of oven builders and the site also has a great oven builder forum.

My second choice was: where should I build it?

I had already planned a backyard kitchen area but not planned for an oven, so I spent a little time sussing out the best location. I narrowed it down to two possible locations: In a corner of the existing kitchen, or on a new pedestal where I was originally planning to build a (now banned by AQMD) outdoor fireplace. I sought out my neighbor for the final judgment.

It's going to go here. Just need to remove that old fence post... And build a base...



I put together a materials list for the base and oven. Everything but the special refractory oven items was available from West Los Angeles Building Materials. The refractory mortar and insulation game from Laguna Clay in the City of Industry.

By the way, Forno Bravo has a Pompeii oven "kit" that you can order from them with all the materials that you need. It's a very god deal. I had to run around a lot to find what I needed, and I saved maybe $50-$100 dollars versus the kit. I also had to make due with some less than ideal materials.