Candling your developing eggs is one of the most exciting parts of hatching your own chicks.
But not everyone knows how it's done or even what it means. I certainly didn't!
In a nutshell, candling is the name given to looking at the inside of an egg by shining a bright light into it. It's used to test whether an egg is good to go into the incubator, and during incubation to see whether the embryo is developing as it should.
One of my Wyandottes candled at day 5 - can you see the developing embryo and blood supply?
Talk to older people who used to incubate and they'll tell you it's called candling because it used to be done with - well, with a candle.
The egg was held over the flame in a darkened room, and that allowed the person to see through the shell.
Perfect? No, not really.
The problem with using a candle is that they tend to be unstable - and very hot. The last thing you want to do with a fertile egg is cook it. So candles had their drawbacks.
Definitely a step in the right direction, flashlights were not as hot, and a lot more stable.
Even now it's easy to use a small flashlight for candling. You just need a strong light - halogen bulbs are ideal - and either a home-made box or your hand made into a fist.
Dealing with the fist-version first, it works by the light being held inside the fist with the bulb close to the top and the egg balanced on the clenched fist.
The benefits of this are that it's a relatively cheap way of doing it, and it's very simple.
Drawbacks? The main one is that it's very easy to drop an egg balanced on a fist, especially if you're trying to take photographs at the same time. The light also tends to be less strong because some of it is absorbed by the hand.
If you're not sure whether you're going to hatch again (although I guarantee you will!), you may not want to invest money in a commercially-made candler.
A home-made candler isn't difficult to achieve and can be very effective. Have a look at this short video to give you an idea of how it can be done.
This is the modern equivalent of both the candle and the flashlight and is very easy to use. Powered by batteries, its light is not hot but strong enough to give an excellent view through the shell, especially if used in a darkened room.
Use it with an 'ovascope' and you have the perfect combination.
Why is candling important?
You can use candling for three reasons : to make sure that eggs are the best possible quality before they go into the incubator, to watch the embryo develop during the 21 days of incubation and to discard eggs which are not developing before they have a chance to spread bacteria to others in the incubator.
Candling can also help to analyse problems if you have a poor hatch rate.
Will candling tell me if an egg is fertile before it goes into the incubator?
No. The only way of knowing whether an egg is fertile - short of breaking the shell open - is by
incubating it for six or seven days. If you candle then, you
should be able to see a small embryo forming together with some
spider-like veins. Have a look at this picture to see what that looks like.
I usually leave eggs in the incubator until day 10 before I discard them. If I see nothing by then, it's time to take them out before they explode and cause bacterial damage to others.
How often should I candle my eggs?
How is it done?
It really isn't difficult. Particularly if you're new to candling eggs it's a good idea to use a soft surface so that, if you do drop one, it has a better chance of surviving. I use a folded towel.
Candling should be done in a darkened room, otherwise you won't be able to see anything very clearly.
Place whichever candler you're using on the surface and turn it on. Carefully take the egg from the incubator and stand it on top of the light. If necessary, cup your hand behind it to help you see better.
Candling in daylight won't work - you need to find a darkened room, or use an Ovascope.
How do I know what I'm looking for?
If you're new to candling, you will need help to gauge whether what you're seeing is what you should be seeing.
My step-by-step guide to hatching covers exactly that with text, images and video-clips. You can find out more about it here.
Does it matter which way up the egg is?
Not really. Fertile eggs should
always be stored with their more pointed end downwards and you can begin
candling in the same position. However, if you can't see clearly it can
sometimes help to turn it the other way up.
Does moving the egg when I'm candling damage it?
No, as long as you're careful and as long as you don't candle after day 18 of incubation. You will generally need to turn it to see what's going on inside, particularly as you come to the later stages of incubation.
Commercially-made ovascopes like the Brinsea have a turning wheel to help with this; otherwise just use your hand but be careful - eggs slip easily.
How long should the egg be out of the incubator?
As little time as possible. If you're just checking whether it's damaged or developing, candling should only take a few minutes. If you've got children who are keen to see what's going on inside, it may take longer.
As a 'rule of thumb', you shouldn't keep it out of the incubator for longer than thirty minutes absolute maximum. I try to candle when the incubator is cooling down for an hour, as it does each day.
Marking eggs during candling - is it safe?
It's perfectly safe to mark eggs as you candle them, and I find it helps with keeping an eye on progress.
Using a pencil (don't use a marker pen - the ink can infiltrate the shell), mark the day it was candled together with whatever your 'shorthand' is for "developing", "not developing" or "not sure".
It also helps to mark the air cell at intervals so you can see that it's still growing, particularly during the final stages when it's hard to see much else inside the egg.
This will tell you, once the chick starts to 'pip' - break through the shell - whether it's in the right place or not.
I also mark each egg either with its breed and with a number which I then keep on a chart.
This allows me to keep tracks on which eggs have been most successful and to look at possible areas where I can improve the likelihood of a good hatch.
Candling is a really fascinating experience, but it helps to know what you're looking for.
My free, day-by-day guide to incubating, candling and hatching your own eggs gives you exactly that.
To find out more, have a look at this page, or fill out the simple form below to get free emails delivered straight to your inbox with step-by-step guide.
These pages have been written with the first-timer in mind but have enough information to keep more experienced hatch-a-holics happy too.
Click on any of the links to go to that page.
... Or you'd like to share how your hatching is doing, please feel free to come over to my friendly Facebook community, or leave a question here.
Some links on this page are affiliate links, which means that
if you purchase a product through them I receive a small commission. There is no extra cost to you. This helps me keep the information on the website free of charge. It also helps support my
family and my chickens! Because my integrity and your satisfaction are very important to me, I
only recommend products I have purchased or would purchase myself and which I believe
would benefit you. To learn more please see my affiliates disclosure document.