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Constructing an Egg Incubator 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 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. 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. Cut off the top of the inside box along the line made in step 2. 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. 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. Mark a line on the flaps of the outside box where they come in contact with the inner edge of the inside box. 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. 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. 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. Place the cake tin, that will cover about one-half of the surface area of the inside box, under the hardware cloth screen. 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. 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. Hatching Failures Eggs do not hatch for reasons which may or may not be the fault of the person caring for the eggs. Below are a few common reasons for incubation failures. 1) Infertile eggs. Buy fertile hatching eggs from farms having at least one rooster with every ten hens. Avoid seasonal temperature problems by getting hatching eggs in the spring. Fertile eggs can be purchased from Asian supermarkets or Trader Joes. 2) Parent stock are weak, unhealthy, or fed a nutritionally deficient diet. Buy eggs from farms that care for the breeder flock by following sound poultry management practices. 3) Eggs are too old or improperly cared for before incubation. Care for the eggs as described. Do not store eggs for longer than 7-10 days before incubating. 4) Shell contamination. Incubate only clean or slightly dirty eggs cleaned with sandpaper. Do not wash dirty hatching eggs or allow eggs to sweat before placing them in the incubator. 5) Temperatures too high, too low, or too variable. Check incubator temperatures with an accurate thermometer, and adjust the thermostat accordingly. 6) Too little or too much humidity in the incubator. Obtain a hygrometer and measure the humidity before making further adjustments. 7) Eggs not turned often enough. Turn eggs at least two or three times daily. Commercial hatcheries turn eggs every two hours. 8) Improper ventilation resulting in oxygen starvation. Be sure all ventilation holes are open in still-air incubators. Forced-air incubators should start with vent openings half-opened. Increase ventilation after ten days until openings are fully opened at hatching time. 9) Rough handling of eggs. Ordinary handling does not harm the embryo because of the protection provided by the egg and amniotic fluid. Excessive handling and jarring of eggs while turning, especially during the first week, may be harmful.