Some notes on eggshells, continued

A few posts back I suggested briefly soaking shells in vinegar to loosen the membranes. After experimentation I’ve changed my mind and method.

The shells do get pitted from the acid, which becomes apparent after they are dyed. This picture shows the results – the uneven patches of color show where the vinegar has eaten a little deeper. The dye - red food color, water and vinegar - is a little acidic so it probably contributes to the pitting as well. If this is the effect you want, then this is how to get it. I’m looking for a smoother surface, so I’ll be skipping the vinegar bath.

As it turns out, warm water works nearly as well. After soaking for five minutes, the inner membrane peeled out with no problem, easier than it would have if fresh (these shells had been sitting around for a while). The result is a shell with more even color and a smoother surface.

Later soaking in acidic dye baths should kill any bugs that may still be clinging, but you can add a few drops of bleach to the water bath if you feel better about it. Watch it closely though because bleach can damage eggshells if too concentrated.
The thinner outer membrane, which is firmly attached to the shell, doesn’t come out so easily, but it didn’t with the vinegar either. You can rub it out with your thumb, but this tends to cause the shell to crumble. I will be trying a few mosaics with this thinner membrane left in. Hopefully it is thin enough and firmly enough attached that the glue will still bond with the shell itself. I may learn otherwise – stay tuned.