Lockdown and Hatching — What Happens in the Final Three Days
The Science of Incubation — Part 7
We're approaching the most exciting part of the incubation journey. After 18 days of careful temperature, humidity, and turning management, your developing chicks are almost ready to make their grand entrance into the world. But the final three days are where science and patience collide — and understanding what's happening inside those eggs can make all the difference between a successful hatch and a disappointing one.
This is where the concept of lockdown comes into play, and it's arguably one of the most critical phases of the entire incubation process.
Understanding Lockdown: Day 18 and Beyond
Lockdown is a specific point in the incubation timeline — typically at day 18 for chicken eggs — when we make four simultaneous changes to our incubator management:
- Stop turning: The automatic or manual turning mechanism is switched off completely.
- Close the incubator: We seal it up and commit to not opening it again until hatching is finished.
- Raise the humidity: We increase relative humidity to between 65–75%, significantly higher than the 40–50% we maintained during incubation.
- Leave it alone: We resist every impulse to check, peek, or interfere until the hatch is complete.
That last point is often the hardest for incubator enthusiasts, but we'll circle back to it because patience isn't just a virtue during lockdown — it's essential.
Why We Stop Turning
For the first 18 days, turning has been crucial for preventing the embryo from sticking to the shell membranes and ensuring even development. But by day 18, everything changes. The chick is now large enough that it needs to assume its hatching position.
This position is very specific: the chick's head is tucked under its right wing, with its beak pointed toward the air cell at the blunt end of the egg. This isn't random — it's a precisely evolved position that allows the chick to access the air cell for its first breaths and to position itself for breaking through the shell efficiently.
If we continued turning the egg, we'd be rotating the chick out of this critical position every few hours. Instead of settling in and preparing for hatch, the chick would be tumbling around, unable to coordinate the complex process of internal pipping and shell breaking that's about to begin. In effect, continuing to turn past day 18 is counterproductive and stressful for the developing chick.
The Humidity Shift: Why Higher Humidity Matters
During the first 18 days of incubation, we kept humidity relatively low — around 40–50% relative humidity — to ensure the egg lost water at the right rate. This water loss is essential; without it, the air cell wouldn't grow, and the chick's respiratory system wouldn't develop properly. (If you've read Part 1 of this series on gas exchange, you'll remember how critical the air cell is for the developing chick's breathing.)
But the final three days are different. Once the chick internally pips and breaks into the air cell, the membranes lining the inside of the shell become exposed to the incubator's atmosphere. In low humidity, these membranes dry out rapidly, becoming tough, leathery, and potentially impassable. A chick that's trying to break through a membrane that's hardened in dry air faces a much steeper challenge — and many chicks don't make it through.
By raising humidity to 65–75% during lockdown, we keep those membranes supple and easier for the chick to penetrate. The chick still has to work to break through, but we've avoided creating an artificially difficult barrier that could prevent an otherwise healthy hatchling from emerging.
The Internal Pip: Days 19–20
Around day 19 or 20 (the exact timing varies slightly between chicks), something remarkable happens inside the egg. The chick, which up until now has been breathing through the porous shell and shell membranes, is ready to take its first true breaths using its lungs.
To do this, the chick must break through the inner membrane — the membrane that lines the inside of the shell — and enter the air cell. This moment is called the internal pip.
The chick uses a small, hard bump on its beak called the egg tooth to create this crucial breach. As it pushes through, air from the air cell floods into the chick's lungs, and for the first time, it's breathing atmospheric air rather than drawing oxygen through the shell.
If you're listening carefully during this phase, you might hear something unexpected: peeping. That sound you hear from inside the egg isn't distress — it's the chick vocalising. Some researchers believe chicks may communicate with their siblings, or they may simply be reacting to the sensation of first breathing air. Either way, hearing peeps from your lockdown incubator is a wonderful sign that the internal pip has occurred.
Simultaneously, the chick's yolk sac — which has been gradually retracting into the body cavity throughout incubation — is now being fully absorbed into the chick's body. This yolk provides the chick with enough nutrition to survive for 24–48 hours after hatching, which is why newly hatched chicks don't need food or water immediately. They're living off stored reserves, courtesy of nature's brilliant packaging system.
The External Pip: Days 20–21
After the internal pip, the next stage is breaking through the shell itself — the external pip.
Using that same egg tooth, the chick begins hammering away at the shell from the inside. Usually, the first breach appears somewhere on the wider, blunt end of the egg, close to where the air cell is located. You might see a small hole or crack — this is the external pip. At this point, the chick has access to fresh air flowing directly into the incubator, rather than just the air cell.
Here's where patience becomes essential: once a chick has externally pipped, it may rest for many hours before making any further progress. This is completely normal. The chick is working hard — exhaustingly hard — and it needs rest between efforts. The urge to help can be overwhelming, but interference at this point rarely helps and often causes harm.
A chick that has externally pipped might take 12–24 hours to fully emerge. Some hatch quickly; others take their time. As long as you can see the chick is moving and progressing, rest assured that things are unfolding exactly as they should.
Zipping: The Final Emergence
Once the chick has rested and gathered strength, it begins the next phase: zipping. The chick rotates inside the egg, using its egg tooth to cut a line around the circumference of the shell — roughly at the equator of the egg. This creates a cap that the chick can eventually push off.
When enough of a line has been cut, the chick pushes with all its remaining strength, the cap pops off, and the chick tumbles out — wet, exhausted, and absolutely miraculous to witness.
The entire process from external pip to emergence typically takes 12–24 hours. If you're watching closely, you'll see little movements, hear faint peeping, and perhaps notice the crack line slowly expanding. It's mesmerising, but it's also a time to cultivate patience and trust in the process.
After Hatching: The Importance of Not Interfering
Once a chick has hatched, it will be wet and exhausted. Leave it in the incubator. Resist the urge to remove it and move it to the brooder immediately.
Over the next several hours, the chick's down will dry and fluff up, transforming it from a bedraggled, wet creature into a fluffy, adorable ball. This fluffing process is essential — wet chicks lose heat rapidly and can become chilled. The incubator provides the warmth and humidity needed for this final stage of post-hatch development.
Here's the critical part: do not open the incubator to remove hatched chicks if other chicks are still pipping. Every time the door opens, humidity drops rapidly. For chicks that have internally pipped but not yet externally pipped, a sudden humidity drop can cause the exposed membranes to shrink-wrap around them — essentially trapping them inside the shell. This is one of the most preventable sources of hatching failure.
Instead, wait until the main hatch is complete before removing chicks. Once all chicks have hatched and dried, you can safely move them to your brooder setup.
The Hardest Part: Patience and Resisting the Urge to Help
Let's be honest: watching a chick struggle to hatch is emotionally difficult. The urge to intervene — to help the chick break through the shell or membrane — is powerful and completely understandable.
But here's the science: a chick that successfully hatches on its own has demonstrated sufficient strength and coordination to survive. The effort of hatching isn't a flaw in the system; it's a feature. It strengthens the chick's cardiovascular system, helps clear fluid from its lungs, and ensures that only chicks capable of surviving make it through.
Assisted hatching — manually helping a chick out of the shell — should only be a last resort, and even then, it should only be considered if the chick has been externally pipped for more than 12 hours with zero visible progress and the membranes are visibly dried and hardened. Even in these cases, assisted hatching is risky and often causes bleeding or other fatal complications.
In the vast majority of cases, patience — even uncomfortable, nail-biting patience — is the right choice.
A Word on Malpositions
Not every chick pips in the ideal position. Some chick eggs hatch from the wrong end, or at an awkward angle. These malpositions are one of the common causes of hatching difficulty and are usually related to either the initial positioning of the egg at the start of incubation or developmental issues within the chick.
A chick that pips from the wrong end of the egg or at a steep angle may take longer to hatch and is at higher risk of getting stuck. While there's not much you can do once a malposition has occurred — the position is set early in development — understanding that malpositions are a natural variation in hatching outcomes can help you respond with realism rather than panic if it happens.
Looking Ahead: Troubleshooting Failed Hatches
Not every lockdown results in a perfect hatch. Environmental factors, genetics, and occasionally operator error can all affect hatching success. In Part 8 of this series, we'll dive into troubleshooting — how to identify what went wrong when hatches don't meet expectations, and how to adjust your management for better results next time.
But for now, focus on nailing these final three days. Lockdown, humidity, patience, and trust in your chicks' ability to hatch themselves — that's the formula.
Over to You
Have you experienced lockdown and hatching? Do you have questions about what's happening inside your eggs right now, or concerns about your current hatch? We'd love to hear from you — leave a comment below or get in touch. At Uneek Poultry, we're here to help you succeed.
Happy hatching!