Vinegar is eggshell kryptonite - but without it, egg art would not be nearly as eggciting.
Eggshells are mostly calcium, and vinegar is acetic acid. Acid dissolves calcium, which means that if you soak an egg in vinegar for two days, the eggshell will completely disappear.
This fact can be very useful when we use eggshells for crafts, and in the craft of egg art, particularly if you have some baking soda in water handy, to stop the acid action when you want to.
Egg dying crafts use this acid etching to drive the dye deeply into the eggshell. The stronger the vinegar portion of the dye solution, the more vivid the color... But a lot of vinegar can weaken the shell, so there is a balance between art and destruction.
Wax applied to the shell, usually in patterns (but blobs work too) will keep the dye away from the shell, and that is the heart of the art of psyanky... Batik on eggshells.
All of the egg arts involving dyes use this acid action in some way. But there are huge differences in the amount of vinegar needed depending on the type of egg being decorated.
A chicken egg will need the amount most dye packs suggest, one teaspoon per bath to one tablespoon. But goose eggs will need much more, and quail eggs much less.
Most blown goose and duck eggs have already had an acid bath because in their straight-from-the-nest form, they are a craft nightmare - dirty and gray, not a bright white canvas.
Waterfowl nest on the edge of water, so their eggs have super tough membranes to protect the chick. Actually, these membranes take up the dye better than an acid bath could ever manage, but they also take up dirt and mud and scratches... So they get scrubbed or sanded or acid washed before sale.
This is why serious psyanky artists often get fresh eggs straight from local farmers.
But with plenty of vinegar, meaning half a cup or more, dye crafts on goose and duck eggs still work well... Just test the effect first, and do give the egg a short baking soda rinse at the end, also testing that step in advance. We have second grade, cost effective eggs that are ideal for testing.
To really see what vinegar can do to an egg, join a child in the most common science experiment in grade school. Leave a fresh chicken egg in a bowl of vinegar and watch the shell bubble off. What's left is the egg in a transparent membrane, no shell.