To store farm fresh eggs and maintain optimal quality, ensuring that the farm fresh eggs contain no cracks or blood spots is a very important step in ensuring successful storage. Eliminating farm fresh eggs that are not of the best quality will enable the remaining farm fresh eggs to have the longest possible storage time, regardless of your storage method. Determining the quality of farm fresh eggs can be achieved by using an egg candler to candle the farm fresh eggs.
What is candling?
Candling is where the farm fresh egg are placed over a light source to illuminate the inside of the egg so that you can see blood spots, cracks and the air pocket. Candling of eggs is usually done with an egg candler.
Why should I candle my farm fresh eggs?
Candling determines suitability and quality of the farm fresh eggs for storage and/or farm egg sales. Only using the perfect eggs for these purposes will ensure that your customers only get the best quality and for your own use it will help to ensure that your farm fresh eggs will store unwashed for up to 3 months in the refrigerator, for over a year when you water glass unwashed eggs and for up to 8 weeks if washed and stored in the refrigerator.
Candling will also determine those farm fresh eggs that are not perfect due to cracks and blood spots. If you are looking for ideas on what to do with these cracked eggs, be sure to check out my post on What to do with cracked eggs.
What is an egg candler?
An egg candler is any device that allows for light to be concentrated under the farm fresh egg. There are commercial egg candlers available, but a flashlight will work as well.
If you are using a flashlight, something to ensure the light is concentrated under the farm fresh egg is a must to properly illuminate the egg for candling purposes. I used a flashlight with my hand cupped over the light end for a long time and although it worked, as you can see in the photo with my hand cupped around my Hybridlight, it was not efficient and the bright light was hard on the eyes at times
To increase efficiency and make things easier for me, I built myself a counter top egg candler using an old metal coffee can, a light socket, a piece of cardboard, a piece of toilet paper roll and a 60 watt LED bulb. It works like a charm.
How to build a homemade egg candler
To build the homemade egg candler, I drilled a hole in the side of the metal can through which I threaded a two wire electrical chord. I put a two prong plug on the end outside of the can and on the inside I used a standard electrical socket and an 8-sided electrical box. Wire the socket by attaching the bared wires to the two spots on the back of the socket and attach the socket to the electrical box. The electrical socket and box does free float in the can but I drilled two holes in the bottom of the can to allow for the electrical box set screws to rest in. You could take those out and permanently attach the electrical box to the metal can, I just never did. 
The light bulb wattage is an important consideration. As you can imagine, it can get warm inside the homemade egg candler so for the longest time I used a small 40 W appliance bulb and then switched to a 40 W round chandelier bulb. But I was finding that with the farm fresh brown eggs, I was missing some of the hair line cracks that were in the eggs and it was causing problems with farm egg sale quality. So, I switched to a 60 W LED day light bulb. It is a bright light that does not throw off any heat and it illuminates the egg very well.
To finish off my homemade egg candler I cut out a lid for the metal can out of a piece of heavy cardboard a bit bigger than the metal can. In the center of the cardboard I cut a hole the size of a toilet paper roll. I taped the two components together using duct tape. The toilet paper roll will hold 99% of the eggs up so that you can roll the egg around to inspect it. For the smaller eggs, I just support it with my finger so it does not fall through the hole. The homemade egg candler just makes life a bit easier. 
How to use the homemade egg candler
I always wash all the farm fresh eggs and allow them to dry before starting the candling process. Washing them will eliminate a few cracked eggs because they can not handle the process of washing. But for those that do survive, once dry, candling is a clean, relatively easy process that will aid you in discovering the cracked eggs, those with blood spots and help determining the freshness.
If you are planning to water glass your farm fresh eggs you should not wash the eggs nor refrigerate them. Washing the egg removes the bloom which is necessary to be intact for this long term storage method. When you refrigerate the eggs, they need to be warmed to room temperature again prior to water glassing and the warming process will cause the farm fresh eggs to sweat, thus breaking down the bloom. Therefore, refrigerating of farm fresh eggs is not recommended. For a great tutorial on water glassing farm fresh eggs, click here.
Set the egg onto the plugged in homemade egg candler and roll the egg slowly around looking for imperfections in the farm fresh eggs. Be sure to check the top and pointy end of the farm fresh egg. But what are you looking for?
How to use the homemade egg candler - a perfect farm fresh egg
While rolling the egg around over the light of your homemade egg candler, you will notice a darker circle that typically is in the large rounded end of the egg. In this photo, notice the slightly darker area in the center of this white shelled farm fresh egg. That is the yolk. If your hens are free ranging or you are feeding garden scraps the yolk will be a darker color and show up almost like a black blob.
Brown shelled farm fresh eggs can be a little harder to see, but with the 60 W bulb in the homemade egg candler, it illuminates it well. In the photo below, the yolk is on the right hand side of the farm fresh egg appearing as a large circle.
Sometimes, double yolk farm fresh eggs can be seen.
You will also be able to see the air pocket on the large end of the egg. The size of the air pocket is indicative of the age of the farm fresh egg. The larger the air pocket, the older the egg. This is an air pocket from a 10 day old unrefrigerated egg.
How to use the homemade egg candler - blood spots in farm fresh egg
Although the odd blood spot in a farm fresh egg is normal, excess number of blood spots are indicative of a too high of a protein in your chickens diet. Blood spots will show up as a black spot when candling your farm fresh egg. 
How to use the homemade egg candler - cracks in a farm fresh egg
While gently rolling the egg around the the homemade egg candler you may notice lighter areas in the surface of the farm fresh egg shell. They can be almost any shape or severity. But when cracked, the farm fresh eggs should be handled differently. Be sure to read my post for information on What to do with cracked eggs.
The severity of cracks in farm fresh eggs can vary depending on what caused the crack. They can be fairly severe...
or a straight line very visible crack. Notice how the light shines through the crack.
Or, they can be a hairline crack that you can almost miss. Notice the small line of illumination in the bottom right ending in a small light spot. This is where having the higher wattage bulb in the homemade egg candler really helps as you will not feel it on the egg nor see it with the naked eye.
The cracks can be almost not detectible. You won't feel them on the surface and almost miss them.
But, a little light side pressure will cause the crack to be fully illuminated.
How to use the homemade egg candler - bad egg
Sometimes the hen will hide or bury an egg and I will not find it for some time. When I do, I have no idea and add it to the fresh farm eggs not realizing it is bad until it floats in the water or I see it while candling. The dark black spots move around easily indicating the egg has spoiled. Discard the egg.
Although candling your farm fresh eggs is a little extra work, I feel it is a critical step in the storage and quality control for farm egg sales and own use. By taking the little extra time, it helps to ensure success with with farm fresh egg sales and storage.
Do you candle your eggs?
Please be sure to join the My Boreal Homestead Life community and follow along as we explore this Homegrown, homestead life in a modern world.