The light green eggs are the ones I can see the veins in the best. I can see some in the brown but not as well and not all of them show veins. How long should I wait to determine if the others are developing?
Usually by
day 10 it's obvious in most eggs (exception are those dark Marans or Wellsummer eggs where you're lucky to see an air cell)
By day 10 there's usually a shadow (embryo & veins) or a brightly glowing egg ball (infertile). The glowing clear eggs can be tossed. If you see a red ring going all the way around the egg, it's bacteria not a vein and should be tossed. (research blood ring for a pic)
Any ? eggs can be marked and left in for another eval in a few days. I used to candle the eggs once a week (7, 14, & 18 days). Now, unless it's for teaching purposes, I only candle all the eggs once sometime between 10-14 days.
Here's what I do, but take with a grain of salt because I'm not an expert..... just an incubation addict with experience LOL
Sometime between 8-10 days - I keep eggs in turner & just touch my bright flashlight briefly to each egg to make it glow. (1 doz eggs takes about 20 sec) Any that look empty get removed and carefully candled for signs of life. If I can't be certain it's a dud, I mark with an X to look at later. I also take 2-3 good sample eggs and trace the air cell line with pencil. I used to do all, but it's not really necessary. I now prefer not to chill eggs by candling often or for a long time. Marking the air cell and seeing how it grows is a way to guide your decisions on humidity. If it's too small you'll get mushy chicks or chicks can drown in fluid while hatching. If too large, difficult to hatch b/c chicks don't have enough room to move into proper position.
Sometime between day 14-18, I recheck and toss any previous ? eggs.... if I'm sure. Again, with those dark eggs I may never know until after the hatch. I also retrace the new air cell line to check growth on those few sample eggs. This is the reference most people use.
Some people weigh eggs and calculate the mass lost. That's actually more accurate, but an eyeball estimate is good enough for me. As with keeping chickens, everyone has opinions but there's no proven guaranteed, 100% hatch every time method. There's just the thrill of getting the best hatch you can.
Day 18 = lockdown procedure. Stop turning and increase humidity. Wait.......
* Your incubator should do this automatically. Just fill both water channels and make sure vent is open
Why remove undeveloped eggs?
Year ago (classroom days long before keeping chickens) I candled with the students but never threw out bad eggs. I figured that more eggs = hope. Then on day 20 after several eggs had pipped, I enjoyed seeing movement and hearing the peeping eggs. I was excited and tapped my finger on the incubator.... because it made the eggs wiggle and peep in response. Then pop! One egg in the middle that was weeping exploded. Fowl smelling slime covered many eggs that were next to it and dripped into the water tray below. I quickly put the eggs on paper towel with the lid over them and washed out the bottom half of the styrofoam incubator. I wiped off the lid & eggs and put them back as quickly as I could. The classroom still smelled bad on hatch day, but not as bad as it did when the egg had popped. Only 4 chicks out of 16 eggs.
I had 9 dead embryos and most of them were full sized with the yolk partially absorbed.
