Introduction: Styrofoam Forced Air Egg Incubator V 2.0

In order to hatch fertile chicken, duck, turkey or other domestic poultry eggs, you need a broody mother bird, or an incubator. If you have the money for it, you can buy extremely functional styrofoam incubators for just over $100 (and smaller, 3-4 egg "classroom" dome models for less yet). And of course you can always pay a lot, lot more. But if you don't want to spend that kind of money, it is still possible to put together a functional "forced air" box incubator at home for just a few dollars, using items you may have around the house or can buy readily at any grocery, thrift, or drugstore (except for the thermostat, which you'll find at Home Depot or other hardware store.)

My total cost for the incubator in this Instructable was about $30. Your cost may be less if you can salvage or re-purpose parts you already have around the house.

Estimated assembly time once you have all the bits together: about 2 hours

You will need:

Serrated knife or hacksaw blade
Duct tape
Electrical tape
Tin snips
Leather gloves
Wire cutters
Wire stripper
Sharpie pen or other marker (to mark on the wire and cooler, not the eggs)
Vacuum cleaner
Pencil (to mark the eggs if desired)

1 styrofoam ice chest, the thicker-walled the better (I got my Omaha Steak shipping box free by asking on Craigslist.)
1 bottle lamp assembly (Home Depot, about $10 - I salvaged mine from a lamp from a thrift store for $6)
1 lower-element, single pole water heater thermostat ($7.57 at Home Depot)
1 25 W bulb
1 12 Volt transformer (from any defunct electronic device)
1 PC Core fan (scavenged or a dollar or two - I got mine from PC Recycle for $2)
1 plastic (preferred) or glass from an inexpensive picture frame ( I salvaged mine for $1 at a thrift)
1 shallow dish for humidity
Wire hardware cloth (about $9/roll if you don't have leftovers from another project)
Aluminum foil

1 indoor/outdoor probe type thermometer/hygrometer, about $12 at Home Depot or Walmart
1/2 C salt
1/4 C water
Large zip-close plastic bag

For candling: 1 Mag-Lite flashlight or other similar extremely bright light
A source of freshly laid, fertilized eggs (NEVER refrigerated)

To increase humidity rapidly: a spray bottle of water

Step 1: Put Window Into Top of Cooler

Remove the plastic or glass from a picture frame. I think plastic is safer, less prone to breakage. Place it on top of the cooler and trace around it. Remove the 'window' and set aside..

With your serrated knife or hacksaw blade, cut inside the marked line at least 1/2", so that the window overlaid on it has a solid area of support, all the way around.

Tape in place with duct tape. I use yellow because it's what I had in my garage.

Step 2: Put Lamp Assembly (heat Source) & Thermostat Into Cooler

Cut a small hole in the end (or side near the end) of the cooler, about 4" above the bottom. The lamp assembly runs through this.

Some lamp assemblies have a hole in the side of the base of the lamp, through which a wire can be run. Mine did not, so I had to drill a hole.

Split the two halves of the long wire. Cut the ribbed half off another 8" and reserve that piece. and strip all ends about 1/2".

Wire according to the diagram below. The wiring diagram has been borrowed and adapted from AK Michelle's 'Home Made Brooder' page at


I will also give written instructions:

Run the wire from the outside, through the lamp base, through the wall of the cooler. You will now be working with the wire inside the cooler. Tie a half-hitch in the wire where it will sit in the cup-shaped base of the lamp assembly. Run the long, non-ribbed wire out through the side-hole in the cup base. Pull snug. Attach the stripped end of the non-ribbed wire to terminal #1 on the thermostat

Run the reserved piece of wire (I have used a piece of orange 12ga wire for this, so you can see where it's going) through the side-hole in the cup also. Attach the outside end to terminal #2 on the thermostat.

Attach the stripped end of the ribbed wire to the silver terminal on the lamp base.

Attach the stripped end of the 8" piece of wire (coming from terminal #2 on the thermostat - orange, in my pictures) to the brass terminal on the lamp base.

Put as little wire inside the cup base as possible, for snug fit when you assemble the lamp assembly. Press the rest of the lamp assembly together. Screw a 25W bulb into the lamp socket.

Put a piece of electrical tape over the terminals on the thermostat, for safety.

Plug in. If you've done it right, the light will turn on. If you've done it wrong you'll probably have a circuit breaker pop. If the breaker didn't pop and the light didn't come on, check the switch on the lamp assembly, which might be turned off. If both of those fail, try a new light bulb.

At this point it is useful to turn the thermostat as close to 99F as you can estimate, put the lid on the cooler, and leave it alone for a few hours. If all is well, the light will turn on and off as the temperature in the cooler reaches or drops below the desired temperature.

Step 3: Install PC Fan Into Cooler

This is a 'forced air' type incubator, which mostly means there won't be cold and hot spots inside the incubator. You don't need much of a fan to accomplish this: a simple PC core fan will do the job nicely.

I have used a hot glue gun to attach square legos to the back side of my fan, as spacers, so the fan isn't smack up against the wall of the cooler. You might use a bit of the leftover styrofoam from the lid, if you like, instead. For this fan, I have tried attaching it to the wall with bits of wire hanger. I find this allows a lot of vibration and thus more noise than necessary, but I have not yet found a tape that will stick to styrofoam, so there you go. You can experiment with how to best attach the fan to the wall. I like to attach mine so it blows across/above the light bulb, moving the warmed air.

Cut the jack off the end of the power cords on the fan. Poke a hole through the wall of the cooler, just large enough to run the wires through to the outside. Strip the ends of the red and black wires, about 1/2".

For power, you need a 12V transformer. Any old 12V 'wall wart' transformer will do: I have used one from a long-defunct baby monitor, and one from a phone charger. Cut the jack off and separate the two halves of the wire (You will end up with black and black with white stripe, or similar). Separate the two a few and strip the ends about 1/2".

Plain black goes to red; black with white stripe, goes to black. Yellow is ground and gets nothing, although you may wish to just put a bit of electrical tape over the end anyway. Twist the stripped wires together and cover with wire nuts or with electrical tape. Plug in and test. It should run smoothly and near-silently.

Step 4: Calibrate Your Thermometer/hygrometer

Mix 1/2 cup of salt and 1/4 cup of water to make a thick slurry. Put your thermometer/hygrometer into a large zip-close plastic bag with this cup of salt slurry, close completely, and leave at room temperature for several hours or overnight. Do not let the water actually touch the hygrometer. If at the end of this time the relative humidity inside the bag is 75%, you're home free. (You should read it while it is still in the closed bag, because the second you take it out, the humidity in your house will begin to affect the reading.)

If the humidity is higher or lower, however, you will need to make a note of the % by which the hygrometer deviates, and always remember to mentally add or subtract that percentage during incubation to maintain the desired humidity:

For example, if your humidity reading is 80%, you must always subtract 5% from whatever you see on the hygrometer. If it says 40%, you will know the real humidity is 35%.

Step 5: Make Wire Floor for Incubator

For this you absolutely need sturdy leather gloves and tin snips. The ends of the wires are viciously sharp and will tear your hands up.

Measure the dimensions of the bottom of your cooler. I say it this way because some coolers (like mine) are narrower at the bottom than the top, and if you only measure the top and make a wire floor from those measurements, it won't fit. It may also, if you are using styrofoam, simply tear up the inside of the cooler, trying to fit it in there.

Cut a piece of wire to size, plus 2" in each direction.

Cut a 2" square out of each corner.

Fold down the sides to a height of 2", so that the corners meet neatly. and the floor is as flat as you can make it. Place an empty, shallow water dish on the bottom of the cooler, then Install the wire floor over and above it, with the thermostat on top of the wire floor at the same level the eggs will lie. Make sure the water dish underneath is shallow enough that it doesn't interfere with the lay of the wire floor. DO NOT ADD WATER YET.

Step 6: Create a 'safe' Area for the Light Bulb, Fan, and Thermostat

Cut a piece of hardware cloth about 8" tall. Cover the top edge with duct tape. Bend to form an enclosure for the light bulb and thermostat.

Put a piece of aluminum foil between the light bulb and the wire, to deflect the direct heat away from the nearest eggs. You want a steady temperature on every egg.

Step 7: Cut Ventilation Holes

There need to be at least 4 ventilation holes, 1/2 - 1" square, at about the level of the wire inside, cut through the walls on the sides. Reserve the pieces of styrofoam removed for plugging it back up again during the last 3 days before hatch.

Eggs "breathe" and developing chicks need lots of oxygen. You need adequate air exchange inside the incubator for the chicks to live and grow.

You may have noticed in my intro, that I also put a ventilation hole in the lid, and covered it partially with duct tape. I find this lets me regulate humidity better without opening the lid (can uncover the top hole, as rising heat carries excess humidity away until the hygrometer reads the desired number, then cover partially and check frequently at first to make sure it holds the % humidity you want.)

Step 8: Add Humidity

This is a very simple step - effectively, you fill the dish in the bottom of the cooler/incubator with warm water AFTER YOU HAVE FINISHED ALL OTHER CONSTRUCTION. You want the temperature to be as close to 99.5F as you can provide, with the humidity to be about 50% for the first 18 days, and about 70% for the last 3 days. This increased humidity at the end is so that when the chicks pip their shells, the membrane inside the shell stays lubricated, and the chicks can move around inside and 'zip' their way out of the shell. If the membrane dries out, the chick can become stuck and simply die in the shell. Proper humidity therefore can literally be a matter of life and death.

If your humidity remains too high despite fiddling with the 'exhaust' ventilation hole in the lid, you may need to remove surface area (ie, take out the large wide dish, and put in one with a smaller bottom/less surface area for evaporation). NEVER LET THE BOWL GO DRY. It may help to leave a couple bits of styrofoam floating on the surface of the water. When you look in, make sure they're still floating - you'll be able to see the water level by where they are.

Water also functions as a thermal mass, helping to regulate the temperature inside the incubator.

For further information on the scientific technicalities of incubating eggs, I refer you to the "Now What?" page at

Step 9: Stabilize Your Temps and Humidity

Put your calibrated thermometer/hygrometer into the bottom of your incubator, with the water wiggler lying directly on the wire (or otherwise at the same level as the eggs will be).

Run your new incubator for at least 2 days, empty except for water in the bowl, until you are satisfied that the temperature and humidity will remain stable (temperature 99-100F, humidity 50%) without you constantly fiddling with it or having to fuss over it. During this time, you can adjust the thermostat a tiny bit at a time, and adjust the number of open or partially-open ventilation holes, waiting an hour or two between adjustments to see how the change will affect things.

Be patient. I'm sure you want to put eggs in instantly, but the incubator needs to be set up as a stable environment first. You'll have better chances of a good hatch if you can take the time to make sure it's holding steady.

Step 10: Add Eggs...and Wait

When you have run your incubator for at least 2 days and checked many times a day to ascertain that the temperature remains within the 99F-101F range, you may add your eggs.

In a commercial incubator, eggs are held upright, big end upward, and turned mechanically several times a day. If you want to stand them upright, you can put them in an egg carton (with the bottoms of the compartments cut off for better air circulation). Cut some 1.5" - 2" blocks of styrofoam from your left over piece, and use these to alternately prop up the long sides of your cartons. The intent is to put the eggs first at one 45 degree angle and then the other, every 12 hours at least.

Alternately, you can mark the eggs on opposite sides with a pencil, then lay them directly on the wire, turning them at least twice a day (gently flip or roll) so (supposedly) the chick doesn't stick to the inside of the shell.

Note: when you first put the room-temperature eggs in, the incubator will take several hours to come up to working temperature. This is okay, and normal. The incubator has to bring the eggs' own thermal masses up to 99-100F. The more eggs you put in, the longer this can take. This incubator will hold at least 2 dozen eggs in cartons. I think it will hold more if they're just lying on their sides.

On day 18, stop turning the eggs, or remove the tilt-blocks (if using the egg carton method), add more warm water to the bowl in the bottom, use your spray-bottle if necessary, bring the humidity up to 70%, and do not open the lid. If you want to observe, observe through the window. The chicks need the eggs to hold still, so they can orient themselves properly to peck themselves free of their shells.

Normal hatching time is 21 days. If your temperature is a little high, they may hatch in 19 or 20 (not desirable). If your temperature is a little low, they may hatch in 22 or even 23 days (again, not desirable). If your chicks don't hatch on day 21, yet you hear pecking or peeping, be patient and DO NOT HELP. If you feel a desperate need to help, check the forums at for advice. Human help usually kills hatching chicks.

Do not open the lid until all chicks have hatched. If you MUST open the lid, use your sprayer to bring the relative humidity back up to 70% immediately - even a minute of dry air can 'shrink wrap' a chick inside the membrane inside its pipped shell.

Step 11: Candle for Viability After 4-5 Days

By 4-5 days of incubation, veining should be visible through the shell of a light-shelled egg, if you have a bright enough light. I use a Mag-lite. Handle gently and make it quick - while I have personally seen broody hens get up and wander off for a bite, a drink and a stretch for up to 15 minutes at a go (and the eggs survive this neglect), you don't want to let them cool off too much.

At the time of this writing, I have successfully hatched a single duck egg in this incubator (his name is Sherman and he has gone back to the farm to live). I now have 14 chicken eggs in it, with a hatching date of July 30.


admin made it!(author)2009-06-15

This is a great Instructable, but you need to add a main image of the final project to the intro step. Please do that and leave me a message when you have so that we can publish your work. Thanks!

butterfly+awsome123 made it!(author)2016-02-10

how can you make a incubator out of card board

diy_bloke made it!(author)2016-06-19

in the same manner, but insulate it with styrofoam

mukasaquraish made it!(author)2015-08-03

hi, boss I failed to get a Styrofoam ice chest in my country, can I use ice cooler that has the outer part made from plastic (the outer part of it is made from plastics)?

chotii made it!(author)2015-08-03

I think anything that's insulated and can hold a steady temperature will work. I now recommend buying an actual incubator disk thermostat, as it will hold a much more precise temperature than a water heater thermostat, but I did manage to hatch eggs using the water heater one.

david319q made it!(author)2014-03-10

Would you suggest using a dimmer switch

B37 made it!(author)2013-05-10

I don’t know if this is still an active article or not, but will try. --- A lot of very good information. I am wondering, if when calibrating a hydrometer using the method of a saturated salt/water solution, how accurate will this be at various temperatures, especially around 100 degrees F. TNX

chotii made it!(author)2013-05-11

The honest answer is, I don't know. I now use an electronic hygrometer/thermometer (like Oregon Scientific) - the kind you'd use inside your own house. I try to incubate around 30-35% humidity until the last 3 days, when I bump it up to about 70%. I get very good hatches from local eggs that have not been shipped. My suspicion is that as long as you're in the ballpark, healthy eggs will hatch. There must be a great deal of variation in nature, after all - temperature and humidity both.

CC+Switchblade made it!(author)2012-01-31

Would it matter if you put the lamp and fan on the lid vs the side?

chotii made it!(author)2012-01-31

I think the important thing is to have the light bulb not touch the window, the walls, or the lid. The higher the bulb, the more the air will have to be forced back down to where the eggs are. Whatever else you do, make sure the temperature is stabilized at as close to 99.5 for at least a day inside your 'water wiggler' on top of an egg carton or however you choose to incubate the eggs *before* you put any eggs in. The temperature near the lid will always be higher as the heat rises significantly.

I have never tried putting the bulb on the lid.I can't think of a good reason not to.

amioten made it!(author)2011-08-08

I like this instructable because since i made one of these i made over 40 chickens and still hatching ducks!!!!!

dbriggs1347 made it!(author)2011-07-06

What did the internal temperature of the water wriggler range from?

chotii made it!(author)2011-07-17

I have seen the internal temperature of the wiggler range between 97F and 102F without harm to the chicks. I aim for as close to 99.5F as possible. Put the wiggler at the same level as the eggs (I have even laid it on top of the eggs). If you lay the wiggler on the floor of the incubator, but use the egg-carton method of incubation, so some eggs are tilted up and some down, you'll find that the temperature in the wiggler registers as much as 2 degrees less than the eggs are getting a few inches higher. It's really amazing how much of a difference a couple of inches make, even with the fan blowing in the incubator. I have toyed with the idea of trying to make the fan blow down at an angle but have not accomplished it yet. Anyway, if the wiggler is at the same level as the eggs, it will record the correct internal temperature for the eggs at that elevation in the incubator.

dbriggs1347 made it!(author)2011-07-20

I know what your saying. What I actually did was raise the platform for the eggs up a couple inches and lowered the fan to match the height of the platform. By doing this I also increased space for more eggs. It was a double win.

qclark made it!(author)2011-07-17

Hi, I've been working on my incubator for a couple of days now and am having a problem with the temperature fluctuating from as low as 93.3 clear up to 103.3, bad thermostat? (i'v tried placing it behind and infront of the aluminum and still have problems)

chotii made it!(author)2011-07-17

Which kind of thermostat are you using, the 'lower thermostat' for a water heater, or a disc thermostat designed for incubators? I eventually gave up on the water heater thermostat because of similar temperature swings and wired in a disc thermostat:

I find as long as the thermostat INSIDE THE WIGGLER stays between 98F and 102F (but ideally as close to 99 as possible - I mean, brief spikes to 102 have NOT killed my whole hatch), it's okay. I've hatched 6 or 8 broods out now using the same incubator but with the disc thermostat.

The more water mass you have inside the incubator, be it the water tray underneath for humidity, a couple of small bottles of drinking water, or a larger quantity of eggs, the more stable the temperatures are going to be. I've been experiencing problems with the end of hatch, as I take chicks out and the reduction in mass inside the incubator seems to confuse things. I have now 3 different indoor-outdoor thermostats with probes inside the single wiggler. They each register slightly different temps, and I average the 3.

However, a 10 degree fluctuation definitely needs adjustment and possibly a better thermostat.

Chicken+Spit made it!(author)2011-04-22

You've only done one duck? Wouldn't it make sense to hatch as many as you can even if you just sell them? I'm definitely going to make one of these. I and a neighbor have been discussing buying one to share but this would be so much more convenient and cost effective. Thankyou very much!

BoogieWipes made it!(author)2011-03-26

Hi there I have 1 rooster and 11 hens and there all laying and i'm eating them and I had an idea and I was thinking breed for money. Awesome

michael3966 made it!(author)2011-03-18

on the wire floor add 4 inches to the width and length after your measurements, that will add the 2 inch fold .

undrline made it!(author)2010-11-23

Doesn't the humidity cause problems with the electrical items (fan/light fixture/etc)?

chotii made it!(author)2010-11-24

I can only tell you that I have never yet run into humidity problems. But most of the time the humidity is 50-60%. It only gets a little higher during hatching. I imagine that the humidity is higher in many parts of the United States all summer long, and I have never heard of problems with electrical fixtures there either.

You're more likely to run into humidity problems in the eggs themselves - too much humidity through the incubation process, and the chicks won't hatch properly. Or they may drown when they pip internally (break into the air cell, which by hatching should take up at least 1/4 of the volume of the egg). If the humidity in the incubator is too high, the moisture in the egg won't evaporate adequately, and the air cell won't be large enough. The chick will drown when it tries to breathe.

pitajames made it!(author)2010-07-26

Fantastic instructable. One of the best I've ever read. Well done.

chotii made it!(author)2010-07-26

Thank you. I just finished hatching out my second batch of the year in this incubator and am picking up eggs from a friend to start another. I need to make a change to it though: I have given up on the water-heater thermostat and now am using the GQF wafer thermostat for the Hovabator incubator: It holds a far steadier temperature with less fussing. I wish I'd just splurged for it before.

josephcrawley made it!(author)2010-03-04

 What's up with the bag around the temp probe? Maybe I missed it but I couldn't figure it out.

chotii made it!(author)2010-03-05

Hi, that's actually a "water wiggler" toy, meant to simulate an egg. The probe goes into the wiggler; the water in the wiggler reaches and sustains the desired temperature; then you know the content of your eggs will also reach and sustain the desired temprature.  You can also purchase "eggs" on Ebay that will perform the same task. People have done all sorts of creative things, like blow the contents out of a real egg, fill it with dishwashing liquid, seal the ends with the temperature probe inside, and put that into their incubator....

I found that water wiggler toy at a local specialty toy store, but they can be purchased in many places, such as local WalMarts.

halolord made it!(author)2009-07-05

You should an egg carton to hold your eggs in, so that they are staying straight and not harming your specimen.

Mr.+Smart+Kid made it!(author)2010-01-13

leaving it straight up the whole time WILL HARM IT.

u have to turn the eggs a few times a day at least

chotii made it!(author)2010-01-13

However! You can put the eggs in an egg carton, small end down, and put a block of styrofoam or what-have-you under one row of eggs (that is, along one long side), and then under the other, at least twice a day. This accomplishes the same thing as 'turning them', and  there is no chance you might accidentally drop an egg (as does happen sometimes when you turn by hand). Also, moving the blocks can be done quickly with little heat loss to the incubator, versus the time needed to turn each individual egg.

I have successfully hatched eggs using this method of tilting the eggs from side to side.

Nemesis201077 made it!(author)2009-11-12

I've spent ages recently looking at creating an incubator, your's is a good example and I'm sure works well. I'm now somewhat obsessed.
I've decided to over-engineer mine as much as possible with automatic thermostat control, fans etc. I work from 6am until 7pm away from home, so want to automate as much of the process as possible. I also want to make it large enough to use as a small brooder as the controlled temperature and seem a good idea.
I'm also going to try and build an automatic egg turner, which is where I'm struggling. I think some Arduino experts may be able to help. Have you any thoughts on automatic turners and how to go about it? They'd make a great addition to any DIY Bator.

chotii made it!(author)2009-11-12

I'm afraid I don't know anything about making an auto-turner, but they've been discussed (right down to gear ratios et al) on in the 'incubating and hatching eggs' forum. With my own eggs, I just turned them by hand morning and evening, and got a 50% hatch rate from shipped eggs (which is average, regardless of what incubator/turning method you use).

Good luck!

Nemesis201077 made it!(author)2009-11-13

I did look on but they all seem to be talking about much larger systems.
I have come up with a cunning plan however, which involves a servo motor with a simple controller that tells it to tilt one way, wait 4 hours, then tilt the other way.
Now all I need to do is learn electronics, soldering, PIC programming and fabrication of the egg turner. EASY!

shelly123987 made it!(author)2009-10-22

Thank you so much for this instuctable! I am so glad that i found this site.
I have been looking for a 'how to' on making a cheap incubator, and this is just perfect! I think i am going to make this (i just have to ask my dad, but i think he will say yes). Thank you for putting pictures up with your step by step instuctions, if you didnt then i would be very lost.
Beautiful job, keep up the good work!

chotii made it!(author)2009-10-22

You're very welcome. the first one I made, working from less detailed instructions / zero pictures, took me HOURS. I hope this will only take you a couple of hours, and not cost much.

dr909 made it!(author)2009-07-09

I homeschool, and my 8-year old wants to incubate an egg for a science project. Your incubator looks like it is simple to build and inexpensive. At the time of publication, though, you had not yet completed the incubation cycle for your own eggs. I am wondering how it worked out. Did you successfully hatch any chicks?Thanks!

chotii made it!(author)2009-07-30

Hi there, I had 6 out of of 15 eggs hatch yesterday and today in this incubator. 2 more may yet hatch. These were 'shipped' eggs bought online, so a 50% hatch rate is average, and I'm pleased! I can tell you now, this design works very well. It really, really needs to be in as cool a location as possible. It's excellent at keeping itself warm; it has a hard time cooling itself off. We're having a heat wave (it was 104F yesterday in late afternoon, and about 90F in my garage) and this incubator occasionally crept up to 102F inside despite sitting on the concrete floor AND having a fan blowing across its surface. The eggs hatched (which just goes to show you they're resilient little creatures) but I've had to really keep an eye on it.

chotii made it!(author)2009-07-20

Hi there, you might want to look at this instructable again - I have completely revamped the incubator instructable, with much better pictures and (now) a proven record of a successful hatch inside it. It does make quite a large incubator, so you know in case your space is limited.

chotii made it!(author)2009-07-09

I got a duck egg to 21 out of 28 days, and then transferred it to a larger incubator with a built-in thermostat (using this set of instructions: ) and the duckling did hatch and was fine. I can't know whether it would have survived in the smaller one.

I will be making a new instructable describing the process of building the bigger-better one (although there are plenty of great instructions over at BYC. Here is the one I like best: but you really need the wiring diagram on the first link above, if you're anything like me. :D

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