It can happen anytime and there is really no time limit. It really depends on the bacteria building up and creating gas. The gas is what usually keeps the air sack from getting larger. Very often the inner membrane blows first and you don't even see an air sack. That is when they are really close to blowing up. The thing is the longer the infertile eggs or bad ones incubate the more like it is that they will blow. That is why I give a week (in ducks), 5 days in chicken eggs if in question but not more. It is better to loose a questionable egg then have it blow up. Here is a good link with pictures for candling. http://www.brinsea.com/pdffiles/what is egg candling.pdf
You have to prorate the dates a little for duck eggs. Add 2 days for duck eggs for every 5 days in chicken eggs.
I use a high lumen, 115 I think, LED flashlight from Walmart found in the camping section.
Katharina
You have to prorate the dates a little for duck eggs. Add 2 days for duck eggs for every 5 days in chicken eggs.
I use a high lumen, 115 I think, LED flashlight from Walmart found in the camping section.
Katharina