Hi, and Bye M'lord
Hmm not quite sure, but see this: SHARPIES on EGGS? Sure! post #10857 & the age old question Can you write on a hatchin egg with sharpie. answer is yes with proof
If the links dont work, go to the first page of this thread, click on the link to the article, and find the "candling" section.
I'm happy for you!