> I bought 2 of the pens they recommended, but the ink runs
> too much while printing.
As to the running, there is an issue with some inks where if you wash the
eggs, you need to make sure they are good and dry otherwise there can be
a lot of ink bleeding. Chicken eggs are particularly troublesome this way.
I like to bath them in some warm water with a dilute amount of vinegar: the
vinegar actually etches/dissolves away a little of the outer surface and
helps the ink to take better to the egg. (Also seems to make the sizing
a little more consistent, http://en.wikipedia.org/wiki/Sizing
. Mind you it
doesn't improve or reduce the sizing, just seems to make it more consistent.)
But, back to my point: if you are getting the egg surface wet, then you
definitely have to give it time to dry. Otherwise, you get blotchy printing
from the ink bleeding too much. I actually toss the eggs into a toaster
oven which was previously heated up: helps dry the eggs faster.
P.S. if you do use a little vinegar, don't leave the eggs in for very
long. Even 5 minutes is too long. The vinegar really does start
etching the shells.
P.P.S. I prefer to use duck eggs: stronger and less porous. You can
buy duck eggs on ebay.