Candling

Candling is a method used in embryology to study the growth and development of an embryo inside an egg.

[1] This technique can also be used to assess the quality and development stage of certain translucent plant seeds, especially those of Lilies and their close relatives.

Candling can thus be used to estimate the optimal time for planting seeds that are being stratified.

[2] 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 is carved.