When I use egg to oxidize, or "egxodize" as I like to call it,I clean and dry the jewelry, place it in a zipper freezer baggie(I like the freezer variety because they are thicker and hold up better with heat) and add the hot boiled egg(s) whole. Then I remove the excess air and crush the egg(s) right in the sealed bag making sure to really crush the yolk since it provides the sulfer. The bag is then returned to the pot ,that has been removed from heat, with the hot water from boiling the egg(s) and covered. I check from time to time to see when the result I want has been achieved (if the jewelry isn't dark enough and the water has cooled off I remove the baggie from the pot, reheat the water, remove the pot from heat and replace the baggie)then remove and re-wash the jewelry to remove the egg mush and polish.
~BB :)
Oh! Also... the more silver to be oxidized the more egg needed.

First: Clean your piece of jewelry thoroughly with soap or Dawn liquid before you start. Scrub into the crevices. Body oils and lotions protect your skin by coating it. They will do the same thing here, preventing oxidation.
Believe it or not, this is generally the main reason that any oxidation process doesn't perform well.

Second:This process relies on heat to produce a chemical reaction between the metal and the sulphur fumes. If both the egg and the piece are hot, then the margin for success the first time goes WAY up!

Heat the jewelry you intend to oxidize while the egg boils. You can do this by placing it in scalding tap water.

I also use a slightly smaller container. After it is closed, I float it in the water that the egg was boiled in - again, more heat, more chances to get the result you're looking for the first time around!