Red Clay Brick Oven in the Philippine Islands

[jayjay]

Hello:
I am jayjay and I love on a remote island in the central Philippines.
We build an oven for our birthdays this year. We found a man to
make the bricks. The bricks were made, sun dried and then kiln fired.
The bricks are not all the same size as they were made by hand in a
small mold that made three bricks at one time. The clay was from
different batches and the bricks were made a different different
times. We put up a platform, about 5 hollow blocks high, using
rebar three times in the five rounds. We then put a four inch cement
platform on the base, The base is about 6 1/2 foot wide and 8 foot
long. There is a hold in the side toward the back, to put wood under.
There is a devider about 2/3 the way from back to front. There is an
ash hole and a hold in the very front under the oven door. That area
will catcht the ashes and will also store small items.
We let the platform dry for two weeks. Then we got the bricks
and installed the base of the oven. We then put a ring of bricks around
the hearth, on edge, the end that was 2 x 4''. We put the edges together
so that the 4 x 8'' edge of the bricks showed inward. We then placed
row after row of bricks set in arches so that the top of the arch was 18 inches off the floor of the hearth. We then put in a door, about 20 inches
wide and with an arch of about 15 inches off the floor of the hearth. We
put in a chimney of about 6 x 4 inches, and about 3 foot high. We capped the chimney with a 6 side brick. the chimney draws well unless there is
a big flame in the oven, when such a big flame is accompanied by a roaring fire, the smoke does come out the front of the owen. We will have a door build soon.
After the clay was dry, we encased the clay bricks in about 8 inches of
cement. With the clay we used straight cement and added some salt and a little lime. With the cement over the bricks we added about 8 sacks of
gravel or same and one bag of cement, (portland type), and left the forms
in place throught 14 earthquakes where our small island town was the epicenter. We do not see any cracks in the dome or the oven in general, except a few hair line cracks around the chimney... after a few weeks and little rain, we set small curing fires and after a few days did a large fire.
Our oven did not get the outside of the oven very hot, with the exception
of the front. We built the fire in the front, and then pushed the fire back. We also thought that we saw the white glow on the bricks. Most of the dome was was clear of char.
The flat back still had char. We brushed the floor of the oven and made
dough and then pizza. We did not have the oven hot enough to bake the pizza. We pulled the coals forward, got a blaze going and then pushed the fire back. We baked the pizza with the aid of the fire. The oven was warm about four hours later and it was barely warm in the morning. The front of the oven and the front arch were hot in the evening and very warm in the morning. We guess that our oven is going to need a heck of a lot of our
type of wood to get the oven hot enough to actually back. Most our
wood is 1/2 to 2 inches thick and about two foot long. We hope to find a better source of wood soon.
We need help on knowing when the oven is hot enough. We also need help on how to build a fire.
Our hearth is 3'4'' x about 4 1/2 foot. The inside of the dome is about 2'8'' wide and 3 foot long. The door area is about 18 deep and about 20 inches wide.
We need suggestions on how to get the oven hotter more quickly and how
to keep it hotter longer. We are open to any and all suggestions.
JJ
Philippine Islands

[dmun]

I'm out of my element here, but isn't the Philippines a volcanic island chain? Volcanic pumice, or tufa, is a natural insulator that's been used in ovens since the time of the Romans. There's not much you can do under the oven at this point, but you could add a lot of insulation on top.