Testing Egg Shell Quality

hydrometer eggshellquality

At the Egg Farmers of Alberta, we hold regional producer meetings,so we can share news about the industry, whether it’s from consumer groups, our colleagues at the Egg Farmers of Canada, or information about upcoming programs and events. These meetings are held in January and June, and this week, we held our June regional meetings across the province. We travel from Grande Prairie to Edmonton, then to Calgary and Lethbridge. We always incorporate a fun and educational activity over the lunch hour.

This go-round, we focused on egg shell quality. Egg shell quality is an important component of egg quality, and it can provide insight into flock health and productivity. Factors affecting shell quality and thickness include:

  • poor housing conditions
  • high temperatures
  • excessive sodium chloride (salt) in feed or water
  • flock age
  • bird stress causing acidic secretions in the oviduct and weakening shell integrity
  • antibiotic treatments
  • diseases, including infectious bronchitis and Newcastle disease
  • calcium and phosphorus levels in the feed

There are many more factors that determine egg shell quality, and all of these must be considered by a commercial egg producer. Weak shells, which are prone to cracks, may result in downgrades at the grading station. This may cost a producer premium pricing and/or may result in fees levied upon the producer for poor product quality. It is in everyone’s best interest to ensure hens lay eggs with strong shells.

We wanted to show our producers an easy method of determining egg shell quality in the barn, with items that can be found in their homes. One way to measure egg shell thickness is assessing specific gravity. Specific gravity is the ratio of the density of a substance in relation to the density of water. I don’t understand the physics behind the concept, and I won’t attempt an explanation. In this case, we can measure egg shell thickness by immersing eggs in a salt solution with a specific gravity 1.080. If the eggs sink, their shell quality is satisfactory. If the eggs float, their shells are thin and may be prone to more cracks, breaking, and so on.

We asked producers to bring eggs to the meeting, so we had a good representation of eggs from a number of barns, conditions, and flock ages. We mixed three salt solutions, with varying specific gravities. The weakest salt solution that an egg floats in determines its specific gravity. For example, if an egg floats in the solution with a specific gravity of 1.080, but doesn’t float in the solution with a specific gravity of 1.075, we would say that egg as having a specific gravity of 1.075.  Low specific gravity indicates thin shells and poor egg shell quality. It was evident that eggs from older flocks had a lower average specific gravity, which indicates that older flocks produce eggs with thinner shells. If a producer sees any trends in relation to specific gravity, they may think to look at management and environmental factors that impact production and flock health. In more serious cases, they would call their veterinarian and schedule a flock health visit.

Specific gravity is one of many tools that producers use to assess flock health and well-being. Happy, healthy hens produce high-quality eggs with strong shells.


  1. Bennett, C. (1993). Measuring Table Egg Shell Quality with One Specific Gravity Salt Solution. The Journal of Applied Poultry Research, 2(2), 130-134.
  2. Factors Influencing Shell Quality – http://www.thepoultrysite.com/articles/1003/factors-influencing-shell-quality/
  3. Density, Specific Weight, and Specific Gravity – http://www.engineeringtoolbox.com/density-specific-weight-gravity-d_290.html