How can you dye blown eggs?
A couple of years ago, I got some goose eggshells from a friend. The best solution I could come up with for dyeing them was to fill the shell with water and then (try to) plug the hole with wax. It made for a rather unsightly blob around the hole, and as you said, the plug could lose cohesion at odd moments, sometimes with rather, um, disastrous results.
(For an egg blown the old-fashioned way with two holes, I guess you'd have to plug one hole, fill it, plug the other hole, and then deal with the double failure points.)
I've been blithely saying &quot;plug the hole with wax&quot;, but my experience is that it's far from that easy. I wonder if there's a technique to it that we're missing. (Duct tape? Medical tape? Candle wax instead of beeswax? Haven't tried any of these.)