Candling is a method used in

embryology Embryology (from Ancient Greek, Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, ''-logy, -logia'') is the branch of animal biology that studies the Prenatal development (biology), prenatal development of gametes (sex ...

to study the growth and development of an

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

inside an

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...

. The method uses a bright light source behind the egg to show details through the shell, and is so called because the original sources of light used were

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

s. The technique of using light to examine eggs is used in the egg industry to assess the quality of edible eggs. File:CDC PHIL 10147 – candling, non-fertile egg.jpg, A non-fertile chicken egg, with only a round yolk sac File:CDC PHIL 10148 – candling, fertilized egg, non-viable.jpg, A non-viable fertilized chicken egg, with a thin blood ring encircling the yolk File:CDC PHIL 10149 – fertilized egg, 11 days old.jpg, A fertilized chicken egg, 11 days old, with blood vessels surrounding the yolk

In plants

This technique can also be used to assess the quality and development stage of certain translucent plant

seeds In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...

, especially those of Lilies and their close relatives. Ripe, viable seeds have a visible

within them when viewed in transmitted light, so good seeds can be sorted out from the non-viable seeds and chaff, if desired. Candling is a highly useful method with certain species that germinate erratically or very slowly, as seed germination causes the embryo to enlarge. Candling can thus be used to estimate the optimal time for planting seeds that are being stratified. Care must be taken during candling, as drying or overheating will kill the developing seeds.

In lutherie

In lutherie, candling is sometimes used to check the thickness of the soundboard in various places, especially on lutes and historical guitars. This is especially necessary because these instruments have soundboards which vary in thickness, for instance the area where the

rose A rose is either a woody perennial plant, perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivar ...

is carved. It is also used to check for any flaws in the wood, or to check how tight a joint is, for instance on the centre seam of the soundboard. Traditionally, a candle would be used, hence the name, but usually nowadays a modern light is used, as this is less of a fire risk.

References

External links

Pacific Bulb Society
– Information about candling lily seeds
Candling and grading manual for shell eggs
– 1951 publication on egg candling by Kansas State Board of Agriculture Poultry farming {{poultry-stub