TECHNICAL BULLETIN
                                                     
                                          51011-BK
 
                          WOOD-BURNING OVEN
 
                      by REV. BERTRAND SAUBOLLE
 
This oven was designed and built for use in the Godavari
School in Kathmandu, Nepal. It is built of solid brick, with
a sheet iron door. A wood fire is burned in the oven, the
ashes removed, and the bread slipped in to bake in the heat
retained by the thick brick wall. The oven for the school has
a baking space of about 122cm x 122cm (4' x 4'), but some have
been built with oven floors as large as 183cm x 183cm (6' x
6'). (For larger sized baking areas, of course, the size of
the entire structure has to be adjusted.)
 
The designer and author, Rev. Bertrand Saubolle, is a Jesuit
priest who, in addition to all the time spent in teaching and
mission work in India and Nepal, has developed and refined
skills in such areas as beekeeping, solar heater construction,
production of methane from animal dung, and gardening, Father
Saubolle has been an enthusiastic VITA Volunteer for more than
ten years. VITA welcomes this opportunity to bring notice of
Godavari School and Father Saubolle's work to a wider
audience.
 
Please send testing results, comments, suggestions, and
requests for further information to VITA.
 
                                           Revised May 1981
 
                                           ISBN 0-86619-091-0
 
                                 VITA
                   1600 Wilson Boulevard, Suite 500
                     Arlington, Virgnia 22209 USA
                 Tel: 703/276-1800 . Fax: 703/243-1865
                      Internet: pr-info@vita.org
 
                           WOOD-BURNING OVEN
 
                             (FOR A BAKERY)
 
This oven <see drawing> is constructed of brick and mortar--a cube with an

wbo1x1.gif (600x600)


outside dimension of 183cm (72"). The baking space is 91.5cm
(36") from the floor, measures about 122cm X 122cm (48" X 48"),
and is set back into the face of the brick about 38cm (15").
This inset helps the oven retain heat and provides a ledge or
shelf in front of the door on which to maneuver pans and
things. The chimney is located above the ledge, outside the
oven door.
 
The roof of the baking space is not a dome but a simple arch--46cm
to 56cm (18" to 22") high in the center and sloping to
about 30.5cm (12") high at the sides. There is no slope from
front to back. It is not a good idea to make the arch more than
61cm (24") high,
because a higher
arch requires more
firewood to heat the
oven and also puts
the source of the
radiated heat that
bakes the tops of
the loaves further
away.
 
The floor of the
baking space should
be of firebrick, if
available. Ours is
of the hardest ordinary
building brick
we could find. We
chose burnt bricks
(which are mostly
rejected by masons), not just red baked bricks, but bricks
burnt black, at least in part. As far as possible, the same
kind of bricks should be used for the arch.
 
Below the layer of firebricks, or burnt building bricks, or
ordinary building bricks, ia a 10cm (4") layer of sand and
crushed glass. This, we were told, retains heat better than
plain brickwork. I don't believe it. But since we had plenty of
broken window panes and old broken bottles, we crushed them all
up and mixed them in. Below the sand, if you use it, or below
the firebrick, is just plain brickwork right down to the floor
of the room.
 
Our chimney is a dream. If you construct your oven well,
especially the chimney part, not the faintest wisp of smoke
will enter the bakery. After ten years of use the front of our
oven is not even the least bit discolored. The chimney is
constructed outside the oven door (see drawing) and not through

wbo2x2.gif (600x600)


the center of the arch, as some make it. The chimney should
have an inside diameter of 23cm or 25.5cm (9" or 10"). Ours
rises straight up through the roof. Our bakery is in a
one-story building. If yours is not, there should be no
difficulty in leading the smoke out by the side wall of the
bakery through a metal stovepipe.
 
Make the door-frame of the oven of 3.75cm or 5cm (1-1/2" or 2")
angle iron with the angle facing the brickwork all around, so
that the bricks fit snugly into the angles, and the metal
protects the brick edges from chipping. Suit yourself for the
size of the opening. I recommend 35.5cm (14") wide so that
30.5cm (12") baking sheets can fit easily without tilting, and
say 30.5cm or 35.5cm (12" or 14") high. Have four hooks of thin
iron rod fixed to the door-frame and protruding from it the
width of a brick so as to anchor the frame to the brickwork.
Make the door itself of .32cm (1/8") sheet iron. The bottom of
the door-frame should be fixed flush with the floor of the
oven.
 
The inner dimension of the ledge or shelf just outside the oven
door is the same as the width of the door-frame. The outer
measurement is 91.5cm (36"). This allows maneuvering room
needed to get at the extreme right and left inside the oven.
The ledge is protected with a sheet of galvanized iron which
bends down for several centimeters (inches) in front as well.
As with the floor of the oven, the surface of the ledge should
also be flush with the bottom of the door-frame. All three
should be quite level. This facilitates the shoving in and
pulling out of loaves. The hardest bricks should be opposite
the door where most shoving and scraping take place.
 
Our oven has no back wall of its own. We built it against the
end wall of the room--and for a special purpose. The room
behind our bakery is used as a storeroom for things that need
to be kept dry, especially during the monsoon--things like
flour, biscuits, cake mixes, spaghetti. If you want a room like
this heated by your oven, dig a hole into the wall at the level
of the oven floor, 91.5cm (36") long and 46cm (18") high,
leaving only a thin partition--12.75cm (5") thick, the width of
a brick--between the oven and the room. The room will get very
dry and pleasantly warm. <see drawing>

wbo3x4.gif (600x600)


 
To control the admission of heat, put a door to the dug out
space. This room is excellent for drying wet clothes during the
rains.
 
HOW TO OPERATE THE OVEN
 
Build a fire inside the oven with a good armful of logs. Leave
the door wide open until the wood is all burned. Pull out the
embers and ashes and put the bread in. Then close the door.
 
After baking the bread, the oven is still hot enough to bake
lighter things like cookies, muffins, or buns.
 
The handles for the scraper for removing the embers, and for
the paddle for putting in and pulling out the loaves, could be
either of light wood or of that light metal tubing used for
electric wires--although the metal tubing may get too hot to
handle without some kind of protection for the user's hands. <see drawing>

wbo4x5.gif (437x437)


Make them 183cm (72") long. The paddle blade could be 30.5cm or
20.5cm (12" or 8") of strong galvanized iron or thin iron
sheeting.
 
Note:  Drawings were taken from Cloudburst II article based on
       the original VITA/Father Saubolle design.
 
VITA Technical Bulletins offer do-it-yourself
technology information on a
wide variety of subjects.
 
The Bulletins are idea generators
intended not so much to provide a definitive
answer as to guide the user's
thinking and planning.  Premises are
sound and testing results are provided,
if available.
 
Evaluations and comments based on each
user's experience are requested. Results
are incorporated into subsequent editions,
thus providing additional guidelines
for adaptation and use in a
greater variety of conditions.
 
========================================
========================================