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Humidity and hatching

Humidity in the incubator is the most confusing part of hatching chicks. Unlike temperature, where you can aim for a number that you know works, RH is, well, relative. Relative humidity (RH) is a percentage of moisture present on the air compared to it being fully saturated. Technically, you can’t go more than 100%, though I have seen RH meters show higher than 100.

Why is RH important? During incubation, eggs with live chicks release water vapor and CO2 to the atmosphere. This is normal and necessary or the chicks will drown. If the air is too dry (low RH) then they lose water too rapidly, dehydrating sometimes to the point of death. If the air is too wet (high RH) then they risk drowning, or not being able to maneuver into a position to hatch.

So what is the right RH? It really and truly depends on a number of variables:

  • Porosity of the egg shell – ever noticed some eggs have a glossy surface, while others are more matte? They lose water at different rates at the same RH. Eggs laid early in the hen’s cycle tend to be less porous than later. Some breed have different shell types. I believe that the dark eggs, especially those with a glossy finish, like some Marans and Welsummers, lose water less readily and so need a lower RH.
  • Size of the eggs – This is a simple surface area to volume ratio thing.
  • Age – Eggs that have been stored for a while have already lost some moisture to the air, before they even get into the incubator.
  • Washed vs unwashed – Washed eggs lose some or all of their “bloom” that protects them from moisture loss.

There may be other factors, but you can see from this list that arriving at the “right” RH for a mixed group of eggs is pretty much impossible. So what to do?

Experience is the best teacher here, and I mean experience with a specific incubator and specific breeds of poultry. Some breeds/hybrids are so vigorous and easy to hatch that any RH seems ok, others are more finicky. Peafowl tend to need a much higher RH during the setting phase (before “lockdown” or moving to the hatcher. Coturnix quail want a lower RH during all stages. Turkeys need lot RH during setting and very high for hatching. You get the idea.

Generally, you can only add water to increase RH, if you remove the water and the RH is still too high, that is hard to manage. So, I start out with low RH and increase it if needed (if I get a bad hatch). During the course of the hatching season (Winter to Summer mostly), the RH trends upward no matter what I do. Nice that that correlates to the more porous shells of summertime.

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Is your cheap incubator good enough to hatch chicks?

Recently a friend had a bad first hatch in a new incubator, and asked my advice. I recommended running the incubator without eggs and using a digital thermometer with a corded probe to record the temp in various places where the eggs would sit. A min/max capability is very useful as well. Here is one I bought that seems accurate enough for me:

Draw a diagram of the egg area and write down the min/max in each location. Check areas until you get a pretty comprehensive picture of the temperature gradient. So, how much is too much? I cabinet incubators, I frequently see a temp gradient of a whole degree between the top and bottom shelf. The newest eggs should go on the top and the older eggs moved down to take advantage of the internal heat the growing chicks produce. However, in a tabletop incubator I think 1 degree across the area is too much.

If there is a large gradient, that would indicate that the air flow is not sufficient, or not properly designed. That can be very hard to fix. Clean the fans if the incubator is not new, and check that they are running.

If the temps are pretty consistent across the entire egg area, what’s next? What is the temp you recorded ? Forced air incubators are generally run at 99.5 to 100.0 degrees F. If you are in that range and still had a poor hatch, check the accuracy of the thermometers against a child’s digital fever thermometer. Put it into the incubator, where the thermometer probe is located. Wait about 5 minutes to get the thermometer up to temp, then open the incubator, push the button and close it quickly. The thermometer will record the temp as long as it is increasing. When it finally beeps, remove it and compare it to the thermometer you are testing. If this is the incubator’s thermostat, and it is not matching, try to adjust the temperature “offset” or else adjust your incubator set temp to correct for the difference. Wait a while and retest until you get it in the range of 99.5 to 100.

That’s all I have to say about temps. Humidity is also important, we will discuss that in the next entry.

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Incubation Notes

Cleaning eggs to be incubated

I often have some very dirty eggs that I want to try to hatch. That is not ideal, but for valuable eggs it is worth trying. Some days it seems like all of the eggs I collect are dirty. The recommendation is to wash them in water that is 10 – 15 degrees warmer than the egg. This prevents the porous shell from pulling the dirty water and any contaminants into the shell. I have been doing this for some time now, and for the last year I have used Tek Trol to disinfect the incubator and the eggs.

Hatching in tabletop incubators

I incubate eggs in cabinet incubators, but I try not to hatch chicks in those, as it creates quite a mess and also, I prefer to raise the humidity and drop the temps for hatching. Because the environment needed for hatching is somewhat different, I prefer to hatch in tabletop incubators, not cabinets.


  • Incubation 99.5 to 100
  • Hatching 98.5 to 99.5


  • Incubation 30% – 40%
  • Hatching 60% to 95%

The biggest issue I have with the cheap styrofoam incubators is that they are underpowered and hard to clean. The Genesis from GQF is the exception regarding power, it is digital and has a much more powerful heating element – but it costs more. During hatch, chicks are not nearly as sensitive to cooler temps. They are, after all, mere hours away from being housed in a brooder that is kept around 95 degrees. This makes the cheap incubators more valuable for hatching than for the actual incubation period.

Cleaning styrofoam incubators is another matter. Anything that touches the styrofoam tends to stick or even embed itself. Better made, hard plastic incubators like the Brinseas or R-COM’s are a breeze to clean. To prevent a hard to clean mess, I line the bottom of the styrofoam incubator with a disposable “puppy pad”, like this: 

Cleaning styrofoam incubators is another matter. Anything that touches the styrofoam tends to stick or even embed itself. Better made, hard plastic incubators like the Brinseas or R-COM’s are a breeze to clean. To prevent a hard to clean mess, I line the bottom of the styrofoam incubator with a disposable  puppy pad. You could try reusable cloth towel that are thoroughly washed between hatches, but I find the disposable pads save me a lot of time. Put the pad in first, then the plastic bottom that holds water. Some water might wick up the towels when you are filling the humidity channels, but it will dry safely.

I hate the metal grid that came with my incubator. Plastic grids work much better. If you only have the metal, buy some coarse needlepoint canvas from the craft store. take measurements with you when purchasing, you will need to cut to size.

On top of the grid, I used rubberized shelf liner, overlapping as needed. This stuff is reusable, but it gets quite dirty and will need soaking for a while after each use.

Finally, the unit is turned on and brought up to temperature. This is where the more powerful units really save time. The Genesis can come up to temp in an hour or less. When the temps are where you want them, meaning the interior of the incubator and the water in the bottom are warmed, you can move the eggs into the hatcher.

Separating chicks in the hatcher

What to do if you are hatching multiple breeds or pens and can’t be sure you can tell the chicks apart? You can use mesh bags to keep the chicks separate in the hatcher. I use these supplies:

These baskets have smooth bottoms, so always line them with the non-slip shelf liner. The bags zip closed. I put the eggs into a basket then put it basket and all, into a bag and zip it shut. I fold the extra part of the bag under the basket, then put it into the hatcher.


I want to explain the ones I use and why.

  • cheap digital humidistat and thermometer combos with sensor on a wire that make it placeable anywhere. I put these in every incubator, sometimes several. Good to glance at often as they are precise enough to show issues like faulty thermostats or heating elements. Humidity is usually “close enough” to accurate.
  • IR “gun” – these are so fun to use, esp if they have a laser pointer. I use these for checking floor temps in brooders. Did you know chicks will chase a red laser dot like a cat?
  • Braun ThermoScan 5 Digital Ear Thermometer (IRT6500US) Just got this, but it will be my goto for spot checking the incubators and tuning their thermostats. This is what commercial hatcheries use and their incubator manufacturers recommend. It is a contact thermometer that takes about a second to register a temp of the egg shell. Take the temp around the widest part of the egg, and take several egg shell temps. The “ideal” is 100.2, but .5 either side is acceptable. I tested mine on the few eggs I have in my Brinsea cabinet and they were 100.2. I have been getting very high hatches in that incubator, so now I can tune all my others to be this same temp.

Price shop for the Braun, I have seen it for $29 and another place was over $100 for the same model. The 6 and 7 models are more expensive, but the extra features (remember more past temps, adjust the display color for different temps to indicate fever) are not useful for egg temps.

Last year I used a child’s digital thermometer to check my other thermometers. Not doing that anymore, now I intend to adjust each thermostat to keep the egg shell temp and note the readings of the other thermometers in each incubator, so I can pick up variances quickly, but always go to the Braun for the real check.


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Cabinet Incubators

I have experience with several makes and models of cabinet incubators.


Dickey Incubators

Cheapest to buy new. Sturdy, all wood construction. Excellent basic incubator, this is certainly the best value for the money.

GQF Manufacturing

These are the most commonly used in the US. Parts are readily available from multiple vendors. Often available used and used ones can be a great value if you are handy and can take them apart to clean and replace any parts that have failed. Middle of the road, this is a good choice for a first cabinet, as lots of people can help you with use, care and maintenance.


Imported from the UK, these are expensive to buy and parts are expensive, if you can even find them in the US. New, they come more complete than the others, including egg trays and spacers that are extra for the others. All that said, this is where I put my most valuable eggs, the ones that can be tricky to hatch (geese, peafowl, etc).

General Comments

  • Why do all the manufacturers insist on using cheap hardware? These are major investments that people intend to use for decades, so why not use stainless hardware to avoid the inevitable rust? It could not cost that much extra when building them and you would gain a reputation for quality just from that alone! It just makes sense.
  • Brinsea and R-COM are the top of the line in non-commercial incubators. If you have the money to invest, buy them instead of the cheaper domestic incubators, you will have better hatches. It is interesting to me that on the Strombergs page the Brinsea 580 is exactly twice the price of a GQF 1502, and the 580 holds exactly twice as many eggs. I see many cases where people get 2 or more 1502’s. If you planned to buy 2 1502’s, why not get the Brinsea 580 instead? If I were starting over buyng incubators, that is what I would do.


Follow these instructions to re-calibrate your Command Center 3258

  1. Set your LCD to (SET TEMP 100) degrees and give the incubator time to stabilize.
  2. Turn off the incubator 
  3. Press the Cooler and the Auto buttons at the same time and hold them down
  4. While holding these buttons down, turn power back on to incubator… hold buttons for (6) seconds
  5. After holding the two buttons for at least (6) seconds, release them.
  6. You will see “SET TEMP” and either a (+ or – number) (example: -1.0)  The factory default is -1.2
  7. Use the temperature up or down button to adjust the command center.  (Ex.  If you are 1 degree high (101), then you’ll need to use the cooler button to lower temp. – 1 degree) You can add or take away temperature until it matches the desired instrument (thermometer/hygrometer) you are using.
  8. Run the incubator until your thermometer and LCD are reading as close together as possible. —- Humidity—-
  9. While the incubator is still on, press and hold the cooler and warmer buttons for 5 seconds. When released, the humidity calibration screen will appear. Here you can adjust the humidity to your trusted hygrometer. TO EXIT THIS MODE: Either press and hold the cooler and warmer buttons for (5) seconds and release. Or you can turn off the incubator and then turn it back on again.

Dickey Incubator Instructions

GQF Incubator – replacing rusty screws

I am cleaning and refurbishing my 1502 cabinet incubators. I bought stainless steel hardware to replace the rusty ones that GQF uses. Why can’t they put stainless hardware on a $700 incubator? The environment inside an incubator is warm and humid, perfect for rust formation.

For future reference, or to help others doing the same, these are the specs for the hardware: #8-32 x 3/4 inch flat head machine screws #8-32 x 1 inch machine screws (only a few of these, but you could use them in place of the 3/4 inch ones) matching hex nuts #8 x 1/2 phillips hex head sheet metal screws

I will update this if I replace other fasteners.

Some of the screws were too rusted to extract. I used Duro Extend to treat the screws to delay further rusting. It would have been better to replace these with stainless before they got this bad, but sometimes you have to make do.