An incubator replaces the hen with three disciplines: temperature held steady, humidity held honest, and eggs turned regularly. Get those three right and the machine does the rest. This class walks the full twenty-one days for chicken eggs; duck, goose and quail run to different calendars, though the disciplines are the same.
Before a single egg goes in
- Site the incubator in a room with a steady background temperature, out of sunlight and draughts. A spare room beats a shed or a conservatory, both of which swing wildly between day and night.
- Run it empty for 24-48 hours. Check the reading at egg height with a separate calibrated thermometer: the display and the truth are not always the same instrument.
- Know your machine. Forced-air (with a fan) runs at 37.5 °C. Still-air models read higher at the top of the egg, so set them to about 38.5 °C measured level with the top of the eggs, and trust your manual over folklore.
- Wash your hands before handling hatching eggs, and set only clean, uncracked eggs. A quick candle before setting catches hairline cracks.
Buy a second thermometer and hygrometer before you buy anything else. Every disappointing hatch investigated turns out to have been run on an instrument nobody had checked.
The record card
Print this page or tick it as you go; the marks are saved in your browser, on this device, and nowhere else. One clutch, one card.
| Day | The work | Temp · humidity | Done |
|---|---|---|---|
| Set | Eggs in, pointed end down or on their sides. Incubator already run warm and steady for 24-48 hours before this moment. | 37.5 °C · 40-45 % | |
| 1-6 | Turn at least three times a day (an odd number, so eggs never rest the same side up two nights running), or let an automatic turner do it. Top up water as needed. | 37.5 °C · 40-45 % | |
| 7 | First candling in a dark room. Fertile eggs show a spider of vessels around a dark spot. Remove clears (they were never fertile) and any blood ring. | 37.5 °C · 40-45 % | |
| 8-13 | Keep turning. Resist the lid. Every opening drops the temperature and the humidity you have worked to hold. | 37.5 °C · 40-45 % | |
| 14 | Second candling. The embryo now fills much of the egg, with a clear air cell at the blunt end. Remove any that stopped developing. | 37.5 °C · 40-45 % | |
| 15-17 | Last days of turning. Check the air cells are growing; humidity a touch low is safer than a touch high. | 37.5 °C · 40-45 % | |
| 18 | Lockdown. Stop turning, remove the turner, raise humidity, and do not open the incubator again until the hatch is done. | 37.5 °C · 65 %+ | |
| 19-20 | Internal pip, then the first external pip, a small raised star on the shell. Cheeping from inside the egg is normal and wonderful. | 37.5 °C · 65 %+ | |
| 21 | Hatch day. Zipping takes hours; a chick can rest a long while between efforts. Chicks stay in until dry and steady on their feet. | 37.5 °C · 65 %+ | |
| 22-23 | Stragglers. Late-set or cool-spot eggs can run a day or two over. Give the quiet eggs until day 23 before you call it. | 37.5 °C · 65 %+ |
Candling without fear
Candling is nothing more than a bright torch against the shell in a dark room. At day 7 a live egg shows a dark spot with vessels radiating like a spider in its web; an infertile egg glows clear and even; a blood ring (a sharp red circle with no spider) means the embryo started and stopped. Remove clears and blood rings; they will only sour. If you cannot decide, leave the egg for the day-14 check rather than gamble.
Lockdown and hatch
Day 18 is the last day your hands belong inside the machine. Stop turning, lift out the turner, raise the humidity to 65 per cent or more, and close the lid on your curiosity. The chick is moving into hatching position; opening the lid now drops the humidity and can shrink-wrap a pipped chick in its own membrane.
Hatching is slow. Pip, rest, cheep, rest, zip: a full day from first crack to free chick is unremarkable. Chicks tumble about, knock other eggs, and generally look like trouble; they are fine, and they can stay in the incubator until fully dry and steady; the yolk they absorbed before hatching feeds them for the first day or two. Move dry chicks to a warm, prepared brooder, and give quiet eggs until day 23 before you conclude the hatch is over.
Helping a chick out of the shell is almost always a mistake, and the exceptions take experience to judge. A chick that pipped and is resting is not stuck; membranes torn early bleed.
When it does not go to plan
- Poor hatch from good eggs: check the thermometer first, the hygrometer second, the turning record third. The machine is guilty until proven innocent.
- Chicks dead in shell late on: most often humidity, either too high through days 1-17 (too little air cell to breathe in) or too low at lockdown (a toughened membrane).
- Early hatch or late hatch: a fraction of a degree hot runs the calendar fast; cool runs it slow. Note it on the card and correct next time.
Keep the card. Two or three hatches of honest records will teach you more about your incubator than any forum thread, and if you go on to sell eggs yourself, that discipline is exactly what Class 4 asks of you. The trade stands shelve the deeper handbooks.