An incubator for a science project need not be as elaborately constructed as a commercial incubator. One can be made from cardboard boxes and glass and the other from plywood (or similar material) and glass.

Don't expect 100 percent success in hatching eggs in these or any other incubators. Commercial hatcheries with all their highly automatic and specialized equipment do not average much more than an 80 percent hatch of all the eggs they incubate. Plan on hatching no more than 50 percent, and you may not even succeed in hatching that many.

The following supplies are needed to construct an inexpensive cardboard box incubator that will hold three dozen or more eggs:

• Two cardboard boxes, one 16 inches wide x 20 inches long x 13 inches (or more) high
• One pane of plexiglass, 16 inches x 20 inches
• 1/4 mesh welded hardware cloth
• One porcelain socket and light bulb or one commercial heating element
• Cake tin (water pan) 1-1/2 inches deep x approximately 9 inches x 13 inches
• Glue
• Masking or duct tape
• Newspapers, wood shavings, or styrofoam
• Two brooding or incubator thermometers

Instructions for Making an Incubator

1.      Place the smaller box inside the larger one. The inner box should be higher than the outer box and approximately two inches smaller in both length and width.

2.      Mark a line on the inside box approximately 1/4 inch below the level of the outside box. Use a yardstick to make a straight line on the inner box after it is removed from the outer box.

3.      Cut off the top of the inside box along the line made in step 2.

4.      Use cut-away pieces of the inside box to line the bottom of both the inner and outer boxes where there are openings where the flaps do not meet. If there are no cut-away pieces, cut up a third box to use.

5.      Put glue on the bottom of the inner box, and then center the inner box in the outer one. There should be a one inch space between the sides of the boxes. Secure the inner box until the glue dries.

6.      Mark a line on the flaps of the outside box where they come in contact with the inner edge of the inside box.

7.      Cut off the flaps of the outside box along the lines drawn in step 6. Cut the corner pieces on a diagonal so that they will make a neat, flat corner.

8.      Stuff strips of newspaper lightly into the space between the boxes. Do not bulge the sides of the incubator. Wood shavings, excelsior, or styrofoam can be used in place of newspaper strips.

9.      Use tin snips to cut a 2-inch square from each corner of the 1/4-inch mesh hardware cloth, then bend the projecting pieces of the screen down so that they form legs to support the screen.

10.  Place the cake tin, that will cover about one-half of the surface area of the inside box, under the hardware cloth screen.

11.  Install the commercial heating element as directed in the instructions sent with the unit. If you use an electric light for heat, mount the porcelain socket on a board 6 inches square, then place the mounting board on the screen. Next, place a tube of cardboard around the light. Position the tube so that it surrounds the light and stands like a chimney, but to reduce the fire hazard do not let it touch either the light bulb or the covering plexiglass. An oatmeal box makes a good tube.

12.  Tape the flaps of the outer box to the sides of the inner box. This seals the area in which the insulating material was placed.

A Plywood Incubator

The following materials are needed:

• Plywood
• Plexiglass
• Cake tin - 13 inches x 9 inches x 1-1/2 inches
• 1/4-inch mesh welded hardware cloth
• Heating unit: either a commercial unit or porcelain socket and light bulb
• Masking tape

Click here for a detailed illustration of a plywood incubator.

You may construct the incubator according to the size desired. It can be a small one for only a few eggs, or it can be a somewhat larger one to hold several dozen eggs. The larger the incubator , the more difficult it will be to maintain a uniform temperature. In fact, you may find it important in the larger incubator to put in a small fan (three-or four-inch blade or smaller) with a low revolving rate.

A Still-Air Incubator

The following equipment and supplies are needed to convert a styrofoam chest into a still-air incubator:

• Plastic ice chests, 12 to 16 inches x 20 to 24 inches x 12 to 15 inches
• 1/4-inch welded mesh hardware cloth, 24 inches x 36 inches
• Masking or duct tape
• Heating cable and micro-switch assembly
• Cake tin (water pan), about 9 inches x 13 inches x 1-1/2 inches deep
• Pencil
• Pane of plexiglass, double strength, approximately 10 x 14 inches
• Brooding or incubator thermometer
• Screwdriver
• Razor blade or knife
• Pliers
• Tin snips
• Ruler

Construct the incubator in the following manner:

1.      Plan to construct the incubator well ahead of time. Order the heating cable and micro-switch assembly, and the thermometer. Allow two weeks for delivery. Order and pick up all other supplies and equipment. Read the instructions carefully. Plan to take two hours to construct the incubator. Plan to take three to four hours to check out the incubator.

2.      Assemble all the supplies, equipment, and the instructions for making the incubator.

3.      Make a platform for the eggs and thermometer. Use the tin snips to cut the welded mesh hardware cloth so that it is six inches longer and six inches wider than the inside dimensions of the bottom of the ice chest. Cut a three-inch square out of each corner of the welded mesh hardware cloth. Bend the projecting pieces so they form legs to support the mesh hardware cloth platform. Trim the rough edges of the legs. Cover the jagged edge with tape or turn the edge in so that it will not puncture the surface of the chest. Install the platform and water pan. The platform should fit loosely so that it may be easily removed from the incubator. In preparation for Step 4, make several marks one inch above the screen on all four sides of the ice chest. Remove platform and water pan before going on to Step 4.

4.      Protect the chest. Styrofoam has a low melting point. It will melt wherever it touches the heating cable. Protect it by running masking tape or similar material around the interior of the chest and then fastening the cable to the tape as illustrated. Place the upper strip of tape approximately 2-1/2 inches from the top of the incubator. Place the lower strip on the marks made in Step 3. Place the third strip halfway between the top and bottom strips.

5.      Install the micro-switch assembly. Use the 4-H electrical project recommendations and safety precautions in installing the micro switch assembly. Place the micro switch assembly on one of the end walls of the incubator. The center hole of the bracket should be approximately 5-1/2 inches down from the top of the incubator, and the electric outlet box should be on the upper side of the assembly.

Make three holes in the incubator so the two bolts and the temperature control bolt can be inserted through the incubator and the assembly. A pencil or other sharp tool can be used to make the holes. Insert 3/16-inch bolts from the inside, add the washers, and then tighten the nuts until the assembly is held firmly to the incubator.

Insert the temperature control bolt with the self-locking wing nut through the incubator. Now screw the ether (heat) wafer on the temperature control bolt. Insert the plug of the heating cable into the micro-switch assembly electrical outlet nearest the incubator wall. Insert the pilot light in the other convenience outlet.

Check unit:
- Plug the lead cord in a 110-V electrical outlet
-Pilot light should glow when ether (heat) wafer is not in contact with micro-switch
-Heating cable should warm up when the pilot light is on
-Screw the temperature control bolt clockwise until a click is heard and the pilot light goes out. Screw the temperature control bolt counterclockwise until a click is heard and the pilot light goes on. The resistance wire should warm up when the pilot light is on. Remove lead cord from 110-volt electrical outlet.

6.      Install the heating cable. Tape the midpoint of the heating cable to the top strip of tape at the end of the chest opposite the mirco-switch assembly. Complete installation of the cable by taping serpentine loops to the top and bottom strips of tape. The cable does not need to be fastened to the middle strip of the tape. Do not permit cable loops to touch each other. Replace screen and water pan. Check unit as described in Step 5.

7.      Make a window in the incubator by imbedding pane of plexiglass in the cover. Place the piece of plexiglass on the cover so that the space between the edges of the plexiglass and the edges of the cover are nearly equal. Stop!!! Read and understand the following directions before proceeding.

With the razor, cut around the perimeter of the glass, penetrating the top of the plastic cover to a depth of 1/4 inch. Do not cut through the top. Remove the glass and draw a pencil line 3/4 inch inside each of the cuts made by the razor. This is a smaller rectangle than that made by the razor cuts. Cut all the way through the cover following the pencil lines. Discard the piece cut out of the cover.

Make a line 1/4 inch from the top of the cover on each or the sides from which the discarded piece was cut. With a razor, cut along this line until the razor meets the earlier cut and the strip lifts out. This cut will be about 3/4 inch deep. Insert the glass in the recessed area. Fasten the glass in place with strips of tape. A window can be made in the side of the ice chest using this same technique, but the heating cable will have to be hung straight across and either above or below the window.

8.      Provide for ventilation of the incubator. To provide proper ventilation, it is necessary to make 16 1/4-inch holes in the long sides of the chest. The holes can be made with a pencil or other sharp instrument. The plastic is soft, so proceed carefully. Make four holes approximately two inches from the top and spaced four inches apart. Make four holes approximately three inches from the bottom when measured from the outside of the chest. Space these holes four inches apart.

9.      Test the incubator. Pour 1/4 to 1/2 inch of warm water (about 100 degrees F.) in the water pan. The use of the warm water reduces the length of time it takes for the incubator to warm up. Put the thermometer on the wire platform so that the bulb will be one inch above the platform. Place the lead cord over the side of the incubator. Place the cover on the incubator. Plug the lead cord into a 110-volt electrical outlet. Turn the temperature control until the pilot light goes on. Continue to adjust the temperature control bolt until the thermometer indicates the desired temperature.

10.  Plan to keep complete and accurate records. The best indication of how well the incubator was built and operated is a successful incubation experience.