I quit using those felt tipped pens .
I had a complete batch of 126 eggs not hatch.. I had written a quite a bit of information on each egg, which bird layed egg , dates of set and hatch etc.. I cannot say for sure that is what killed the eggs, but I heard that information about fel tipped pens after that disaster. I switched to pencil..
I figure it this way, why take the chance? just to prove sombody wrong?? that is not important to me..what is important is a good hatch of some (sometimes) very expensive eggs.. Not to mention my time with a wasted hatch..
so you magic marker users out there, keep using them. just do not try to convert me..
in fact I only mark the eggs that I find it necessary to mark with a single letter.. the rest of the information is in a note book or on my large block calender..
I can tell you exactly where each of over 200 eggs in my sportsman is and that cuts down on the time I have to hold the bator open to find the eggs I need to remove..