The study of eggs is called oology and the study of plant and animal embryos is called embryology.  A candler is the key to "seeing" the daily development of the embryo.  By placing a simple cardboard box over a light source it allows the light to become concentrated and it beams out the small hole.  When the egg is placed up against the hole from which the beam of light is shining, it becomes semi-transparent and allows sight into the egg.

Materials needed for candler:

Cut a hole in the bottom of the box so that it will easily slip over a light source (novelty lamps or flashlights will work). Cut a hole level with the brightest part of the bulb, in the side of the box about 2.5 cm in diameter. The candling unit does get extremely hot, so make sure to place the hole on the side of the box so that the egg does not overheat while candling (heat rises).  Use the candler in a dark room with the brightest bulb that can be safely used.

Why candle eggs? 

There are many reasons to use a candler; it allows you to determine if eggs are infertile or whether a bacterial ring or blood spot has developed.  If an egg with a dead embryo remains in the incubator too long it will start to weep and may explode and contaminate the other eggs.

In early stages you can see the porosity of the egg, the working circulatory system, the heart beating, and the eyes.  But by the ninth day candling brings such delight upon seeing the embryo turn and bobble in its shell.  Candling also allows you to measure the responding variable of growth.  If you can get the embryo to hold still long enough you can measure its length.

 

Recording data:

Recording outcomes such as the number of eggs that have been lost due to infertility or met with disease and death (quitters), and the number of healthy births can be easily graphed.  During candling, attempts can be made to measure the length of the embryo using a ruler. Organizing outcomes compares the differences in the two sets of eggs.  My recorded data reflects a high number of bacteria attacks and death mainly concentrated in the refrigerated eggs.

Weight Loss:

Measuring the embryos length progression is only one way to measure development.  Another way to measure development is to weigh the egg.  It is interesting to discover that thriving eggs loose weight while in the incubation stages.  It is typical for eggs to loose 10%-13% of their original weight.  Humidity plays a role as does the consumption of the yolk by the embryo in the final stages of development.