Unless you have a good candling light and light shelled eggs preferably bantam size you aren't likely to see anything at day 4. You may not see anything at day 6. If you have dark eggs or a poor light you may not see anything at day 14 aside from the darkest area of the egg expanding. If you haven't candled several times before and know what to look for then don't bother until at least day 7. When I started hatching I would candle day 7, mark the eggs that looked bad, put everything back, and candle again on day 10 or 11. Then if I was sure and not candling dark shelled eggs I would break the ones that still looked bad. Usually in a few days a bad egg will develop an obvious blood ring or be obviously clear but again this is unless you are dealing with very dark shelled eggs where you may not see anything ever. A few times now with light shelled bantam eggs I have candled nearly every day to see the changes I can still just barely tell if an egg is doing anything on day 4 or 5. I absolutely will not break an egg before day 10 no matter how sure I think I am about it not developing.
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