booklet was prepared by a team of VITA Volunteers
Edmund Hazzard, St. Louis, Missouri
Dr. Robert G. Luce, Schenectady, N.Y.
Jon E. McNeal, Rexford, N.Y.
Ed Gutowski, Schenectady, N.Y.
Jim Curtis, Schenectady, N.Y.
FIRST PRINTING FEBRUARY 1967
REPRINTED FEBRUARY 1976
REPRINTED FEBRUARY 1977
REPRINTED APRIL 1977
REPRINTED AUGUST 1991
1600 Wilson Boulevard, Suite 500
Arlington, Virgnia 22209 USA
Tel: 703/276-1800 * Fax: 703/243-1865
The VITA Solar
Cooker was especially designed to be sturdy, relatively
easy to make, easy to repair, and low in cost. It uses the
of the Fresnel reflector which concentrates light and heat
several simple reflecting surfaces. Most other cookers use a
reflecting surface. The VITA Fresnel design has a number of
-It gives a
broad uniform focal region the size of the cooking
than a sharp, intense spot of heat, making it
safer and more
-Rings can be
added or removed to increase or decrease the
cooker described in this manual is designed to
heat for the cooking needs of a medium-sized
-to use cheap
readily available materials. In the United
materials used are mainly Masonite sheet,
Mylar, wood, and iron strip. In both the United
Morocco, the cost of materials is about three
($3.00). In developing countries the Mylar will have
to be imported
but it is lightweight and inexpensive,
-to be as
simple as possible.
The VITA Solar
Cooker requires more labor than, for example, forming
a paraboloidal reflector by spinning an aluminum sheet; the
may make it uneconomical for developed countries, but this
designed specifically for developing ones.
decides to begin manufacturing this solar cooker, there
are some serious drawbacks that should be considered
carefully. It is
generally agreed that an average of 2,000 or less hours of
year is too little for the cooker to be practical. It should
pointed out that the cooker will be more effective in dry
The cooker is
not effective early in the morning or late in the
afternoon; therefore it could not be used by people who
their large meal in the evening. Also the women must accept
cooking outside in the open.
cooker is not difficult to use once one is accustomed to
it, it does require some instruction. Experience in Morocco
that learning to use it is about like learning to knit;
can probably not expect a "natural" market to
exist; one must be prepared
to follow up manufacturing with personal introduction.
cooker construction is not difficult, spreading the
Mylar on the glued Masonite is tricky and requires some
will probably ruin the first few cookers in the process of
Therefore it is probably impractical to plan on making fewer
dozen or so cookers as a start.
perhaps most importantly, one wants to be sure that
other cooking procedures are comparatively quite expensive.
how much time or money does the average family spend on
and hence how long would it take to recover the initial
savings on fuel costs? This is probably an important
a subsistence agricultural economy where there is not much
Also, of course, the cooker can never be used all the time
so it can
never substitute completely for convential cooking methods.
I. TOOLS AND MATERIALS
lists all the tools and materials needed to build the
Cooker. The best choice of materials may vary from
place to place.
Other kinds of wood or composition board may be
cheaper than the
materials indicated here in some countries. Any
such as plywood or certain sheet metals, can substitute
for the Masonite.
A. Reflecting Surface
blade or sharp knife
window washer (squeegee) or a smooth
rubber windshield wiper
(double print photograph roller)
boards 5 =. x 5 cm. x 135 cm.
coping saw (bandsaw if available)
About 120 cm.
x 120 cm. Masonite (0.3 cm. to 0.6 cm. thick)
as free as
possible of pits and structure defects,
80% - 95%
ethyl alcohol approximately 50 cc/cooker
(resin, hardener, and solvent 80% - 95%
approximately 75 cc. of mixed cement
Clean dry cup
stick (size of pencil)
A roll of
aluminized Mylar (.0005" thickness) 160 cm. wide
paint or if not available use good oil paint
Ruler and pencil
of drilling metal (6 mm. diameter)
15 cm. strip
of 18 mm. x 3 mm. hot rolled iron
Two (2) 2 cm.
x 120 cm. boards (oak for strength but pine
woods are sufficient)
aluminum nails (or screws) about 5 cm. long
10 cm. x 6
mm. bolt with fitting wing nut
C. Utensil Holder
of drilling metal (6 mm. diameter)
or metal cutting hand saw
40 cm. strip
of 18 mm. x 3 mm hot rolled iron
50 cm. strip
of 18 mm. x 3 mm. hot rolled iron
stock 25 mm. x 25 mm. x 80 cm.
preferably a hard wood
Two (2) 25
mm. x 6 mm. steel bolts and fitting wing nuts
One (1) 11
cm. x 6 mm. steel bolt with fitting wing nuts
One (1) 3 cm.
x 6 mm. steel bolt with fitting nut
II. HOW TO MAKE THE VITA SOLAR COOKER
Note: Be sure you feel you can complete all the steps before
Construction can be divided into nine parts:
Applying a sealing finish to the Masonite
Making the surface smooth and dust free
Applying thin uniform coat of adhesive
Applying the aluminized "Mylar"
Cutting out the rings
Preparing the legs
Bending the rings into shape and mounting
them on the legs
Providing a cooking vessel support
Providing an adjustable brace
1. Applying a
sealing finish to the Masonite (to keep the Masonite
glue and moisture).
If the 120 cm. x 120 cm. Masonite is rough
to the touch,
sand it smooth with medium sandpaper. If it
step can be omitted.
Brush polyurethane paint smoothly on both
sides of the
covering all areas. If polyurethane paint is
available, a coat of epoxy cement may be used in
side (the side to be used as the reflector),
or lacquer may be used on the back. Do not
or lacquer on the front.
Let the paint dry on a dust-free area.
Clean the brush with oil base paint thinner (or
varnish, or water for epoxy).
2. Making the front
surface smooth and dust free.
Choose the smoother side of the Masonite as
(or the side
with epoxy already on it.)
Using a safety razor blade, remove major
such as drip
marks, from this front side.
Rub the surface smooth with steel wool or
feels very smooth to the touch. If it does not,
coat of sealer to the smooth side, let it
dry and sand
From scrap wood cut out four (4) wedges 10
cm. long and
5 cm. high as
shown in Fig. 2. These will be used in part 4.
Nail four (4) pieces of scrap wood into a
150 cm. square
shown in Fig. 1. This will be used in step 4.
3. Applying a thin
uniform coat of adhesive. See Fig. 2.
Note: Before you
prepare the epoxy, complete steps 4A and
4B so that the Mylar
will be ready to be glued.
Some important notes to remember about
hardens in about 20 minutes on the
and in a bit longer time when spread
Once hardened, it will not dissolve
hardening it may be dissolved in water,
water is added it will never harden.
tools and containers which touch the
with water before it hardens if you
use them again.
Do not let
water come into contact with the cement
used for the actual cementing.
Do not mix
hardener and resin except when actually
preparing to use it.
Do not put
a spoon covered with hardener into the
Do not put
a spoon covered with resin into the
Mix equal portions of hardener, resin and
80% - 95%
alcohol in a
clean dry cup with a clean smooth stick.
tablespoons or six teaspoons of each should be
Dust the Masonite surface with a clean, dry,
immediately before applying the prepared cement.
Masonite on a table or a similar large flat
preferably above the ground, to lessen the
dust that will settle on the surface while
Pour the prepared cement on the center of
and spread it
evenly over all the surface in a very thin
coat with a
stiff squeegee or rubber blade. Use long,
strokes to prevent ridges and press down quite
Roll the cemented surface with a
double-print roller until
appears shiny and uniform from a glancing
out ridges and regions of varying thickness
by going back
and forth in various directions. Again,
Clean all the equipment within a half-hour.
next step first if you have time.) Don't
let any water
get on the cemented surface of the Masonite
and keep the
surface away from dust. The cemented surface
workable for at least a half-hour.
4. Applying the
Decide which side of the Mylar is
aluminized. It is
of the roll (if the Mylar comes in a
roll) or the
shinier side or the side from which the
be rubbed off with your fingernail and
you can see
the scratches you have made, through the
last test is absolutely certain.
Using a safety razor blade, cut a 160 cm. x
section from the Mylar roll.
Nail the Mylar to the top of the 135 cm. x
135 cm. square
step 2E) with the alumunized side down. Use
or carpet tacks or thumb tacks or staples
every foot or
so, or nail down four (4) wood strips
frame. Stretch the Mylar tightly enough so
that it hangs
down a few centimeters in the center. The
Mylar is very
strong but it tears very easily so be careful
when you nail
See Fig. 1
for the above two steps. If you have a
the easiest way to fasten the Mylar is to
vertically down in front of the frame.
Place the frame over the glued surface of
on the four
(4) wedges with the aluminized side down.
wedges out until the center of the Mylar hangs
a few cm.
above the center of the glue-covered Masonite.
(See Fig. 3)
Apply the Mylar to the Masonite with a stiff
the center outward (see Fig. 3A), using
strokes. Try to keep the Mylar quite taut
glued area and the frame so that the Mylar
does not touch the Masonite until the
pull it down.
If the Mylar rips from the frame and falls
Masonite, it will form many ridges and bubbles.
In any case,
ridges and bubbles are sure to form and the
Mylar must be lifted and reapplied in the
following procedure: spread the Mylar, starting
center as far toward the edges as possible, using
suppled by the frame. Gradually lower the
the force of the strokes rip the Mylar from
the frame. If
serious ridges or bubbles appear far from
free the Mylar from that region either by
frame or by ripping the Mylar from part of
the frame and pulling it upward and outward
by hand. Don't
the four corners as they will be sawed off
applying the Mylar is the most difficult
building the solar cooker; it takes some practice
and you are fortunate if the first few
Trim the overhanging edges of the Mylar with
a razor blade.
With a needle or the razor blade, puncture
all the air
press them down; small air bubbles fixed in
this way are
hardly noticeable afterward.
Clean the surface of any traces of glue with
a damp cloth.
Allow one day for the glue to dry.
5. Cutting out the
rings. (see Fig. 4)
Locate the geometric center of the Masonite
where the two
diagonals meet. Be careful not to tear
Cut out the rings with a coping saw or a
jigsaw if one
using the holes in the supplied template
as radii. It
may be convenient to nail down the center
the whole sheet, keeping the saw stationary.
This may save
the trouble of drawing out the rings.
From the inner ring cut out a section with a
edge of .5 cm.
From the next most inner ring cut out a
a width at
the outer edge of 2.8 cm.
6. Preparing the
Cut Out the two legs, using the template
may wish to
copy the template onto sheet metal.) Use
2 cm. x 12
cm. x 150 cm. pieces of wood. At the
notch one leg
from above and one from below as shown on
so that their edges are flush.
Fit the two pieces together at the 2 cm.
Cut a wooden
tie bar about 40 cm. long (with 45[degrees] ends if
like) and nail or screw it to the backs of legs
so that the
legs form an angle of exactly 90[degrees]. (See Fig. 5)
7. Bending the rings
into place and mounting them onto the
legs. (See Fig.
Place the inner ring (#1) on the frame and
closed at one
of the cross pieces, nailing both ends to the
Nail down the ring at the other places where it
frame as well, using 5 cm. aluminum nails (or
Do the same thing with ring #2; the ring
the slots in the legs.
C. Saw through
ring #3 if you haven't already. Work it
slots on the frame and ovelap it somewhere
crosspieces. It should overlap 8.8 cm.
and 6 cm. on the inner edge. Clamp it into place.
D. Do the same
with the outer ring (#4). It should
19.8 cm. on
the outer edge and 14.5 cm. on the inner edge.
E. Place a light
source about five meters from the cooker
and point the
cooker at this source. Looking at the
about a meter directly in front, adjust
rings #3 and
#4 until the reflection is even all the
all four rings. If the rings and legs
cut, very little adjustment would be
F. When you are
satisfied, there are two ways to fasten
the outer two
rings in place:
the rings by bolting or riveting
through the Masonite where they
overlap, at two or three locations not
on the same radius. Then nail
to the frame; or:
2. Cut a
wider slat in one of the crosspieces
overlap the rings on top of this
crosspiece. Nail through the two
Masonite. This latter method is less
durable and produces a less satisfactory
shape of the outer rings.
G. Clean the
rings with a damp cloth and paint or tape
edges of the rings to prevent weathering
8. Providing a
cooking vessel support.
Any support will
do as long as the pot is placed so that the
pot rests in the
bright focal region about one meter from the
A separate tripod is one possibility.
design is as
Drill a 6 mm. hole about 2 cm. from one end
of a 50 cm.
x 18 mm. x 3
mm. strip of hot-rolled iron. Using a
radial indentations around the hole on one
Bend the strip into a circle of the desired
size to hold a cooking vessel), with the
on the outside of the ring formed. A
form will help.
Drill a 6 mm. hole in the other end of the
strip at the
they overlap to form the closed ring.
directly opposite this one.
Drill a 6 mm. hole 1 cm. from each end of a
40 cm. x 18 mm.
x 3 mm.
strip of hot-rolled iron. Score around
chisel. Place this strip in a vise so
cm. are securely held. Grip the strip
4 cm. from
the vise with a wrench with adjustable jaws;
give a quarter turn so that the end is
the other end. (Fig. 7)
Bend the horizcntal ends to form a
"U" with the chisel
marks on the
inside and the ends about as far apart as
the width of
the ring formed in step B. (Change the
in step D if necessary.) Drill a 6 mm.
center of the bottom part of the "U".
Cut a 2. 5 cm.-deep slot diagonally into one
end of the
(25 mm. x 25 mm. x 80 cm.), a little narrower
mm. Flatten the edges of the rod and
6 mm. hole
across the slot. (Fig. 8)
Secure the metal "U" in the slot
with a 3 cm. x 6 mm. stove
the metal ring between the ends of the "U" with
two 25 mm. x
6 mm. stove bolts and fitting wing nuts, with
between the ring and the "U" if you wish.
Cut a short triangular wooden block to fit
the vertex of the two legs. Nail it in
Take the cooker outdoors.
Rest the support rod in place
vertex of the two legs, place a pot in the metal
ring and aim
the cooker at the sun. Change the
support rod projects until the brightest part of
spot is on the bottom of the pot. Mark
Chisel off the upper edge of the support rod
at its lower
drill a hole down through it, the vertex of the
the triangular wooden block. Bolt the
an 11 cm. stove bolt with fitting wing nut.
9. Providing an
Brace the cooker
in a position facing directly into the sun
so that the
bright focal spot is on the bottom of the cooking
It must be adjusted about every twenty
moves. The angle adjustment can be done
pieces of wood
propped against the tie bar. A better
however, is the
leg assembly shown in Fig. 9. This will
It requires s strip of iron, two 4 cm.
a longer bolt,
and two pieces of wood, one about twice as long
other. Their exact length will depend
on your latitude
and the time of
day the cooker is commonly used.
Anchor the legs
firmly to keep the cooker from being blown
over by the wind.
Mylar and epoxy may have to be imported.
they can be obtained in the United States
chrome metalized Mylar, 160 cm. wide, $1.00
U. S. per yard:
Coating Products, Inc.
West Forest Avenue
Englewood, New Jersey 07631
Astro Special 1100, 8 pounds per gallon
$1.30 U.S. per pound.
Astro Special 2950, 8 pounds per gallon
$1.65 U.S. per pound.
Chemical Company, Inc.
Schenectady, New York 12309
Figure 10. Using the Cooker
1. Install the
support rod in place in the vertex of the two legs.
Aim the cooker at
2. Adjust the
support rod so that the brightest part of the focal
spot hits the
bottom of a pot placed in the support.
hole through the
support rod, the vertex of the legs and the
block. Bolt the rod in place.
3. Brace the cooker
so that it faces directly into the sun, with
the bright focal
spot on the bottom of the cooking vessel.
shadow of the
cooking vessel will be in the center of the cooker.
If the shadow is
outside the center, the cooker is not facing
direatly into the
4. Adjust the cooker
every 30 minutes as the sun moves.
SOLAR COOKER LEG TEMPLATE
This template is to be used to make a 152-cm
(5-toof) template for the legs of the VITA
Solar Cooker. See Paragraph 6A and Fig. 5,
page 11. The complete template is AB (88.5cm)
plus BC (63.5cm). To make the template,
cut out the four pieces shown and
string or a straightedge
to be sure ACB is a
SPECIAL NOTE ON THE VITA SOLAR COOKER MANUAL
Although we are
sending you the VITA Solar Cooker Manuals, we feel
it is important to point out some limitations in its
use. These are
partially covered on pages 1 and 2 of the manual and are
The VITA Solar
Cooker is not useful for day by day cooking in most
circumstances. To be
useful requires understanding of the following
The cooker is probably not practical where
of the hours of sunlight is under
hours per year.
The cooker is not useful for cooking meals
morning or late afternoon.
The cooker must be frequently shifted in
use (once every 10 minutes or so) to take
advantage of the sun's position.
Making a good contact between the Mylar film
backing is tricky and requires practice.
probably ruin a few cookers in the process
learning how to make this seal. For
it is important to order enough materials
few cookers in hopes of getting one good
one. After this techniques
mastered, there is
little material spoilage.
It requires the development of some
with the cooker. This process can be
developed by a trial and error procedure.
experienced people have compared this learning
to be about as difficult as learning how
In many areas of the world the cooker cannot
economically with existing methods of
cooking. For example, one should
would take to recover the initial investment
cooker from the savings on fuel that
about because of its use.
To properly introduce the cooker to a local
populace requires careful thought and painstaking
effort. Those experienced in the
introduction should be consulted to see how it
best be put to use in the given culture.
Aside from local taboos (religious,
traditional, etc.) there will be the very formidable
of resistance to change. People will be
point out the difference in taste (whether there is
not) the longer or shorter cooking times, the
required to store the heater, the need for being
while cooking, etc.
the cooker does represent a method of putting the
free-for-the-asking energy of the sun to work, and if this
accomplished economically in your community, it will bring
advantages of a more smoke-free atmosphere, less real danger
flame, and an opportunity to prove to the local people that
method can sometimes prove to be an advantage over old
thereby reducing that major obstacle to progress,
If you decide to
go ahead with the construction and introduction
of the cooker with full knowledge of its problems and
you think through a plan of introduction, you could well
make a real
contribution to the people of your community.
Do not, however, expect
to quickly build a cooker properly the first time and be
cooking with it on your first try.
Good luck in your efforts.
SOLAR COOKER ADDENDUM
VITA has been
able to locate a substitute for one of the less easily
obtainable materials (aluminized Mylar film) called for in
the solar cooker
substitute is aluminum foil. The
problem of using aluminum
foil, however, is that conventional attempts to fasten the
foil yield discouraging
results (the foil wrinkles easily) and commonly available
and/or glues will not hold the foil to the cooker surface
following procedure, then, will help you over the
difficulties of applying
aluminum foil successfully:
1. Remove the
foil from the roll with a minimum of wrinkling;
2. Apply the
cement in the same manner mentioned in the manual.(*)
apply the cement to not more than one foot of the
surface at any one time;
3. Gently lay on
appropriate length of foil down on the cemented
anchoring one end of the foil with one hand to
4. Smooth the
foil with your right hand, keeping that hand wet
by dunking it
in water (if your right hand becomes dry while
foil, it will tend to bounce along the foil,
5. The foil is
then rolled with a roller. Do not press
6. Repeat the
above process on successive sections of the cooker
the cooker is covered. If too many wrinkles
on the foil,
remove that section and try again.
substitute for the epoxy cement shown in the manual is "waterglass"
(sodium or potassium silicate).
A fairly strong solution of
water-glass when applied as a substitute to the epoxy cement
harden within 20 minutes when placed in direct
sunlight. Note that
"water-glass" will dry most rapidly in dry
climates, so where
extended drying periods are needed, do the gluing in a cool
The water in this mixture will tend to soak through the
it is suggested that you place the masonite disk on a flat
to prevent warping.
And if the glue is too thin, it can be
made more pasty by mixing in a smooth filler powder such as
or kaolin, without affecting its hardness or stregth.
Material submitted by:
Mr. Terance Maaske
IF YOU NEED MORE
manual or on other technical matters, VITA (Volunteers in
Technical Assistance, Inc.) can send it to you.
have specific questions, VITA can put you in contact with
an expert who can answer them.
VITA is an
international association of scientists,
engineers, technicians, businessmen, educators and others
who volunteer their spare time to consult on questions
from persons in developing areas.
Simply send your
Volunteers In Technical Assistance
Boulevard. Suite 500
Post Office Box 12438
Arlington. Virginia 22209-8438 USA
To help the VITA Volunteer who answers your request, you
1. Be quantitative -- give measurements, costs, materials
2. Describe the best solution, if any, found nearby and
3. Indicate a deadline for action.
You will hear directly
from the VITA
Volunteer; keep in contact with him; inform
the VITA Office if
Volunteers in Technical Assistance (VITA) is
a private, nonprofit, international development
organization. Started in 1959 by a group
of concerned scientists and engineers, VITA
maintains an extensive documentation center
and worldwide roster of volunteer technical
experts. VITA makes
available to individuals
and organizations in developing countries a
variety of information and technical resources
aimed at fostering self-sufficiency--needs
assessment and program development support;
by-mail and on-site consulting services;
information systems training.
It publishes a
variety of technical manuals and manuals.