Buckley Rumford Fireplaces
Office Oven
11/11/09

The basic plan is to replace the too-small 16" prototype oven with a Superior Clay 36" oven. The larger oven seemed to fit best obliquely behind the 30" Rumford fireplace and, to save as much space as possible, we decided to make the base circular and follow the hemispherical form of the oven. Since the flue is behind the oven, we laid the flue from the entrance tunnel over the top of the oven dome like a Mohawk haircut.

At 20" above floor level we poured a 4" thick reinforced concrete base, added 4" of insulating concrete made with perlite and vermiculite mixed with one eighth part Portland cement.

Firebox under oven - We decided after studying Larry Carnes' kiln that we would build a firebox directly under the oven. The idea is to build a fire under the oven (and maybe also in the oven) to get the temperature up high enough to use the oven as a kiln. Larry says he can get his kiln up to 2,400 deg. F. The under firebox may also heat the oven without a fire in the oven so there's more room for food or it may become an ash dump or a way to get air to the back of the oven - whatever. This is an experiment. If all fails and the oven floor caves in I can always fill the firebox and lay a new firebrick hearth.

Fit - The oven sections had been around here for over a year and were broken. I fit the broken dome together as well as I could and filled the gaps and parged the whole dome with about one inch of Insulstick.

Insulation - Over the clay oven liner and coat of refractory mortar we parged about 2" of DeltaCrete insulating refractory. Then we added two or three inches of the Portland/Perlite/Vermiculite concrete described below.

    Perlite and Vermiculite were obtained from a local garden store where it is mostly sold to lighten soil. The Perlite came in a 3.5 cu.ft. bag and cost $20 while the Vermiculite was in a 4 cu.ft bag for $30. (See picture of bags) We made samples which seemed similar in weight (light) and strength (weak). The Perlite was dusty and settled to almost half it's dry volume when mixed with about 10% Portland cement and water. The Vermiculite maintained its volume when mixed. Being white, it was easier to tell when the Perlite was thoroughly mixed. All things considered, both products seemed about the same.
After that layer, more to create a bond break and room for expansion than for insulation, we layed about 1/2" of ordinary fiberglass insulation over the dome, held down with metal lath and plastered the whole dome with regular Type S mortar.

Finish - Left the washed mortar finish, blue tile trim and pizza!

Break-in - The first fire we started in the oven and in the firebox underneath the hearth. It seemed to take a long time (three hours) to get up to temperature and, when we thought the oven was hot enough to cook pizza the crust burned before the cheese melted. Interestingly, water seeped out of the oven base enough so that it puddled on the floor. The oven drew perfectly.

Some cracking appeared, especially near the opening where the outer shell was in contact with the tunnel liner. We filled the cracks, when hot, with pure Portland cement which seemed to work in that they did not re-appear in the next fire but left the finish sort of blotchy.

The next time we decided to only build a fire in the oven, thinking that the fire under the hearth made the hearth too hot relative to the oven atmosphere. It was better but still seemed to take long time to heat up.

The next two fires were day-long affairs to try to drive the water out. Probably the seeping water is the excess water used to mix the insulating pearlite and vermiculite concrete. And probably the oven isn't very well insulated as long as the insulation layer is soaking wet.

The picture with the dragon is of the oven after it had been fired for about six hours. All the smoke had been burned off the inside of the oven, indicating (I think) that the walls were more than 1200 degrees F. Cracks have not appeared in the oven liner and the repaired cracks in the outer shell did not re-appear. Water still seeped out. The dial thermometer and the radiant thermometer both seem erratic. Maybe the oven is too hot for their 1,000 degree limit.

Broken-in After a few fires we now can heat the oven up to "clean" (1,200 deg F) in about two hours. I give it another half hour to become fully saturated with heat - then scrape the coals to one side, wash the floor with a wet brush or rag and start cooking. At probably at least 1,000 deg. F, pizza takes about 90 seconds. As the oven cools to about 800 deg.F the pizza takes two or three minutes and maybe is more evenly done. The insulation has dried out, the seeping has stopped, there are still some cracks around the entrance and flue due to being in contact with the lining but it's great fun and a great success - and keeps the office warm.


Mom's Perfect Pizza Dough
(Makes enough dough for six 9inch pizzas)

5 cups unbleached all-purpose flour (see note), plus more if needed
2 teaspoons table salt
1 teaspoon instant dry yeast
2 cups cool water (65 degrees), plus more if needed
Olive oil, for brushing

Mix 5 cups flour, salt, yeast and water with an electric mixer fitted with a dough hook until a coarse ball of dough forms. (about 4 minutes.) Let dough rest for 5 minutes.

Mix again until dough clears the sides of the bowl and barely sticks to the bottom. (Beat at medium-low speed about 2 minutes.

If dough is too soft and sticky to hold its shape, mix in more flour, a tablespoon at a time; if too stiff or dry, mix in more water by the tablespoonful. Let rest for 5 minutes.

Mix again until dough is slightly sticky and supple, 2 to 3  more minutes. If dough is too soft to hold its shape, mix in more flour by the tablespoonful; if too stiff, mix in water by the tablespoonful. (Dough should be translucent when stretched.)

Place dough on a floured counter, and dust with flour to absorb surface moisture. Fold into a ball and place in a bowl brushed with olive oil, turning dough to coat with oil. Cover the bowl with plastic wrap and let stand at room temperature for 30 mutes. Refrigerate overnight. (If making pizzas that day, let dough stand at room temperature for 1-1/2 hours. Punch it down, reshape it into a ball and return ball to bowl. Cover and refrigerate at least 2 hours.)

The next day (or later the same day after dough has been chilled), remove dough from refrigerator 2 hours before making pizzas. It will have expanded somewhat and will be softer and more pliable.

Using a plastic bowl scraper dipped in water or with wet hands, gently transfer dough to a floured counter, deflating it as little as possible. With a pastry blade or knife dipped in water, divide dough into 6 equal pieces. Gently round each piece into a ball and rub with olive oil.

Line a baking sheet with parchment or a non-stick silicone baking liner. Brush with olive oil. Place dough needed to make, pizzas today on the sheet and loosely cover sheet with plastic wrap or a food grade plastic bag; refrigerate if not using within 2 hours. Place extra balls in individual zippered freezer bags; refrigerate or freeze. Use refrigerated balls within 2 days and frozen balls within 3 months.

Let dough stand at room temperature for 2 hours before making pizzas.

Note: If desired, substitute a little wholewheat or other wholegrain flour up to 1 tablespoon per cup –for the all-purpose to give the crust a countrystyle taste.

First time I made this I was on my not buying groceries until we used up all our stores kick so, being short of flour, I added a fair amount of soy flour and oat flour – maybe as much as a half-cup apiece. Worked great!

PIZZA INGREDIENTS

Dough
Flour
Corn meal
Olive oil
Mozzarella cheese
Goat cheese
Gorgonzola
Pears
Artichoke hearts

Sun-dried tomatoes
Mushrooms
Onions
Peppers
Garlic, roasted
Spinach
Red sauce (marinara)
Pesto
Sausage
Pepperoni

Puff Pastry

Superior Clay Bake Ovens
Buckley Rumford Fireplaces
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