Day 24, shall I shut the incubator down.

[wvwzzz]

First time hatching and incubating chicks!

I have a River Systems ET49 Incubator (I am not sure if you get many in the US, it's basically the same as design as the Borotto Real 49, popular in the UK, Europe and Australia). I am not particularly impressed with it, especially how expensive it was. The incubator has turning trays which are replaced at lock down with a hatching tray which sits about 3" lower. The lower height of the hatching tray seems to have cold spots, 34-36 degrees C (93 to 97F). I increased the temperature slightly but couldn't go higher than 38c otherwise it cooks the eggs outside of the cold spot.

Out of the 49 eggs, 37 were fertile and developing on day 10. I quickly candled the 37 on day 18 and they still looked good (very dark with good air cells).

3 chicks hatched on day 20, 13 hatched overnight day 20 and into 21, 10 hatched overnight day 21 and into day 22. 3 hatched late on day 23.

I'm left with 8 that don't seem to have any signs of life. With no pipping I opened the incubator and candled them remaining eggs, 6 look very dead with C shaped embryos, large air sacks, no movement and no veins

1 looks potentially alive, some veins are still visible and if I rotate the egg something moves with the rotation slightly but no other movement and the air sack looks quite small.
1 looks probably dead, there are still some veins but the insides seem very fluid, like a yoke moving around in an unfertilised egg when the egg is rotated.

Shall I keep the incubator going for another couple of days and call it a day?

There were no power cuts during incubation, temperature was set to 37.5 deg c then upped to 38 for during the incubation.
The incubator has a useless manual humidity control but I tried to keep the humidity during lock down between 55 and 70%. I opened the incubator 3 times to remove hatched chicks. The chicks that hatched seem to shoot out of their shells so I think the humidity was ok.

Overall I'm not that happy with the incubator, I will troubleshoot it more after this hatch but think I will try and send it back.

I have attached some pics of the eggs (1st is an example of the 6 dead looking eggs, 2nd is the potentially alive egg and last photo the fluid egg) and some pics of the beautiful chicks!

Thanks!

 

[BoundlessLove]

If there is no smell at all, you could leave for a day or two longer.
Just in case the second egg is not dead.
I have heard of someone here hatching an egg day 25/26. But it is a rare occasion.

 

[ChickenCanoe]

As you have already surmised, the biggest culprit is most likely the inconsistent temperatures. Do you ever rotate eggs to other parts of the incubator on a regular basis? Other than a design change, that is the most immediate fix but not perfect. More permanently, you could change the air circulation apparatus to insure consistent temps throughout.
What shows that is the fact that given a consistent temperature of 37.5C for the duration, you can almost set your watch incubating chicken eggs. Setting at noon on a Monday, they will hatch at noon on the Monday 3 weeks later. Those that hatch a day early had likely experienced at about one degree hotter temp throughout. And alternatively, hatching a day or two late means they were cool. The cooler they are, the less likely they will survive long even if they hatch late. This is because at lower temperatures, different organs will develop at different rates.
This doesn't answer your primary question but I agree with @BoundlessLove. It is unlikely the outcome for the late bloomers is rosy. At this point, other than candling, you could try a float test. Very gently lower the remaining eggs one at a time into water deep enough to detect if there is any movement.

 

[MROO]

If there is no smell at all, you could leave for a day or two longer.
Just in case the second egg is not dead.
I have heard of someone here hatching an egg day 25/26. But it is a rare occasion.

I don't even try to predict when my eggs will hatch, anymore! While most of my hens are Nankin bantams with a consistent 19 day incubation time, others are bantam EEs and Nankin mixes (20-21 days,) one is a large fowl mix (22-23 days) and one is a BJG/Silkie mix (23-24 days.) All dates are tentative, depending on whether mama "started" setting before a broody confiscated the egg or the egglet sat for a bit in-between.

This year, I've had a rash of persistent broodies playing "Musical Nests," so I don't always catch them in time. Unfortunately, I'm one of those fools who can't toss an obviously developing egg, so I ended up with three unscheduled clutches, this year ... all with crazy hatching times!

Twice, I've set aside eggs I pulled after Mama hatched her clutch, intending to toss them out, but got distracted (gotta LOVE that ADHD!) When I picked them up the next day to toss them - one of the "dead" egglets peeped at me! My 'bator is down (I swore I wasn't hatching again!) so the only place to left to hatch was ... ummm ... well, one of those two pullets is named BooBee ...
I give up!

 

[Ridgerunner]

I could not tell if that is a forced air (has a fan) or a still air. A fan should stir the air up so you have a consistent temperature throughout while a still air allows temperature to vary by height since warm air rises. If it has a fan and you got the different temperatures you did it is not working correctly. I'd return it. If it is a still air, that could explain some different temperatures between incubation and hatch as you changed elevations but that still does not explain the differences you got during incubation. I'd still return it if you can.

I've never experienced this but the latest I've read of an egg hatching was after 25 days of incubation. It is unlikely but as long as it does not stink when you sniff the egg it won't hurt anything to wait that long. Just do not get your hopes up.

 

[Debbie292d]

I've never experienced this but the latest I've read of an egg hatching was after 25 days of incubation. It is unlikely but as long as it does not stink when you sniff the egg it won't hurt anything to wait that long. Just do not get your hopes up.

23 days was our longest, for silkies, which typically are early. That was when I first started a few years ago and was stacking too many eggs into an NR360.

I agree with letting it run another day.

That water trick above, by the way, for sure safe for 60 seconds. Beyond that, I don't know. You're not watching for sink or float, you're watching for movement, and I would never do this unless I couldn't candle and needed to.