Candling, Egg testing

Holding an egg up to the light was one way to determine if it was newly laid as described by Hieronymus Fabricius of Aquapendente (died 1619). Candling could also show if the egg was fertilized; or black spots ment the egg was bad. New eggs floated. Glass eggs and rounded egg baskets.


"Aquapendente [Hieronymus Fabricius of Aquapendente, 1533-1619] relates several ways how to know whether eggs are new laid or not; he would have them held to a candle, and then see whether the humours contained therein are clear, thin and transparent; for if they be otherwise, it is a sign the eggs are old, because the effervescence has embroiled and confounded the insensible parts of these humours, and made them dark. Lastly, hold an egg to the fire, and if a little watry moisture slicks to it, it is new; if not, it is old; because a new laid egg is moister than the old, and its humours being thinner, work easier through the pores of the shell." [1763]

Interior of a Kitchen, Pehr Hillestrom (1732–1816) in Nationalmuseum at Stockholm, Sweden -

"A new-laid egg will sink in water, bad ones are more or less buoyant; but this is a tedious way of testing eggs. The best way is to form sort of tube with the left hand, holding with the right hand the egg, close and opposite to this tube, in the light. If the egg is good the meat will look clear, and partly transparent; if bad, it will look dark with black spots in it." [Sanderson, 1846]

"Eggshells are porous or perforated right through by minute holes for the admission of air needed by the chick for breathing. Hence in time a part of the liquid contents of the egg evapotates. The white and yolk shrink and the resulting emptied space is filled with air. This space is normally at the broad end. And this is the reason why, in storing eggs, the point should always be downward.

To test eggs take a candle or electric light or lamp in an otherwise dark room and fit it with a candling chimney, which may be ob- tained at any poultry store or may be readily made from a piece of card- board. This is merely a cylinder of cardboard large enough to surround the candle or the lamp chimney, and having a tube inserted at right angles somewhat smaller in diameter than an ordinary egg, and about the level of the flame. Through this the egg can be observed against the light.

To test eggs, hold each one up against the opening of this cylinder, broad end upward, and look through them at the light. If the contents do not fill the shell, the egg is not perfectly fresh, and the larger the air space the older is the egg. The yolk should be perfectly clear and round in outline. If, besides the air space, there is a dark haze or cloud in the egg, it has become spoiled. If the cloud contains a black spot, the egg is bad." [Morse, 1909]

How to Candle Eggs. M.E. Pennington, M.K. Jenkins. US Depart of Agriculture Bulletin No. 565. May 11, 1918. Info and many colored pictures of scanned eggs HERE

Building an Egg Candling Room. Photos and sketches. Ice and Refrigeration May 1904 HERE

Glass egg in rounded egg basket. The glass egg was put under a hen to encourage it to lay eggs. The basket was shaped to hold the oval eggs. My grandmother was walking to the store swinging one of these baskets. She was surprised when her father followed behind picking up the eggs from the field, caught up with her and stopped her swinging. Forever.

SOURCES

A New and Complete Dictionary of Arts and Sciences. London: 1763
How to Candle Eggs. M.E. Pennington, M.K. Jenkins. US Department of Agriculture Bulletin No. 565. May 11, 1918.
Ice and Refrigeration Illustrated. Chicago: May 1904
Lloyd's Modern Poultry Book Guide and Directory. Chicago: 1894
Morse, Sidney. Household Discoveries: An Encyclopaedia of Practical Recipes. NY: 1909
A New and Complete Dictionary of Arts and Sciences. v2. London: 1763
Sanderson, J. M. The Complete Cook. Phila: 1846


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