the role of the eggshell
The shell of a bird egg is one
of nature’s greatest wonders. It stores
calcium for the embryo to use for growth, conducts
heat, allows water evaporation and also regulates
respiration. But first and foremost it protects
the internal contents of the egg against injury
eggshell is riddled with pores which allow oxygen
to enter the egg and carbon dioxide to exit. Eggs
need to loose weight during incubation and water
vapor also leaves the egg through the pores.
cuticle, the outer layer of the eggshell is the
first defense of an egg. It helps prevent water
and contaminants from entering the pores.
environment that the egg encounters within the
first few seconds after it is layed is critical.
At this time the egg is wet and its pores full
of fluid. If the shell comes in contact with a
dirty surface the film of water on its surface
provides the ideal route for bacteria, viruses
or fungi to enter the pores and move inside the
egg. Once the contents of an egg are contaminated,
cleaning and disinfecting the shell will not remove
the problem. So good nest hygiene and prompt collection
of eggs are crucial.
Prevention is the best control to reduce the number
of dirty eggs.
eggs coming from nests should be clean if the
nesting materials are kept clean.
production of floor eggs can be minimized if
the flock is trained early to use its nest boxes
by adding a few fake eggs.
should be gathered at least once a day or more
often. The longer eggs are left in nests, the
more likely they may be broken or dirtied. For
poultry, nests should be cleaned once a week
to remove dirty litter and manure, and replaced
with clean bedding materials. More often for
under the best conditions, some dirty eggs may
still result. Dirty eggs should be placed in a
separate container so they don’t contaminate
should eggs be cleaned before setting in an incubator?
Not necessarily. In many cases you could do more
harm than good for a couple of reasons:
All sanitizing procedures will remove the outer
cuticle from the egg as well as the dirt and
may leave the egg at greater risk from bacterial
Any cleaning procedure incorrectly followed
can contaminate the egg rather than sanitize
Cracked eggs should be discarded if possible and
should not be wet cleaned.
cleaning with abrasives is an option
for lightly soiled eggs but you run the risk of
breaking the egg. It is time-consuming and weakens
the cuticle. The fine dust created by abrasion
can also be pushed down into the pores, partially
blocking them and causing respiratory problems
particularly towards the end of incubation.
Dry cleaning doesn't work very well to clean up
eggs that have been smeared with the contents
of broken eggs in the nest.
you choose to use abrasives to clean the eggs,
remember to sanitize them from time to time in
water with bleach, and to allow them to dry fully
before use to avoid the same issues as wet cleaning.
cleaning is more complicated. Poor practice
has given egg washing a bad name because it can
cause more problems than it was designed to solve.
basic issue is that dirty eggs are covered with
bacteria, which have trouble getting through the
shell so long as it remains dry. As soon as the
shell is wet, they pass through the shell more
Soiled eggs may be cleaned using a brand egg wash
solution such as Brinsea®
Incubation Disinfectant Concentrate
following the manufacturer’s instructions
but it is essential to wash eggs in solution which
is significantly warmer than the egg
otherwise dirty water will flow inwards through
the pores and contaminate the inside of the egg.
If you cool the egg, the contents shrink slightly,
causing a partial vacuum inside which tends to
pull foreign matter into the egg.
Ideally eggs should be washed in a solution at
(105°F - 41°C) and rinsed in another solution
also at (105°F - 41°C) before being set
to dry on a clean surface. Thereafter they should
only be handled with clean hands.
Egg washers with thermostatic control are available
to ensure the solution is maintained at the correct
Problems to watch out for:
solution too hot (over 122°F – 50°C)
and immersion for too long can damage the
embryo. The egg contents will warm considerably
and the egg will take some while to cool after
it is removed from the solution. The embryo temperature
may reach such a level that it starts developing
but not at a rate that can be sustained long enough
for normal development. Particular care should
be taken with small eggs.
solution too cold (under 104°F – 40°C).
The air the pores will contract and pull some
of the washing solution inside the egg. The embryo
may be damaged by the solution itself or if the
solution is inactive by bacteria.
all the eggs in the same solution. You should
wash the cleanest eggs first leaving the really
dirty eggs for last. It is always best to change
the solution regularly rather than trying to add
more disinfectant to an already dirty solution.
gloves. Rubber gloves can be slippery when wet
and can easily get contaminated. It is preferable
to use freshly washed hands to handle eggs.
sanitizing procedure will weaken the egg’s
natural defense against contamination and should
only be undertaken with great care.
small scale production:
Heavily soiled eggs should be discarded if possible.
eggs are better handled as little as possible
and not sanitized before incubation.
Soiled eggs can be carefully dry cleaned or,
if wet cleaned, only washed in solution significantly
warmer than the egg.
more information on egg handling procedures before
incubation please refer to
our storage and
handling guidelines because the quality
of a chick all depends on the quality of an egg.