They usually hatch within 24 hours of pipping. If you try to assist to soon the chick will probably not make it. You can pick some of the shell around the pip after 24 hours. If you see any blood stop. If you don't see any blood then you can proceed carefully picking a little of the shell off always watching for any blood which usually means the chick is not ready to hatch yet. The pictures show the chick hasn't started to zip yet.
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These are the tools I use to assist. I use warm water with a q-tip to moisten the membrane
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This is a pipped egg starting to zip.
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Here the chick is zipping. This is a Rhode Island White chick zipping.
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