I first learned about dry water marbling several months ago from Cathy at More nail polish. I like this technique because it uses a lot less nail polish and you have more control about the design that ends up on your nail. The other advantage is that you can make the water marble, place it on plastic and keep it for several weeks before you use it. It works best if you let the plastic sheets dry for several days before applying them to nails.
When it's time to apply them to my nails, I will fist hold the dry sheet up to my hand and trace individual nails on the plastic side. This way you can cut them to fit your nails well. A lot of people paint their nails with a white base but I find that it's helpful to use one of the colors in the marble as a base. That way if the marble doesn't fit your nail perfectly, the base just looks like part of it. In my experience china glaze and sally hansen polishes work the best for marbling.
This manicure wasn't cleaned up well but it's still fun to look at. I haven't managed to completely prevent bubbles from forming on the plastic.
I made these sheets several months ago. They were kept in a plastic bag but began to chip after about a month. It's probably best to use them within a few weeks but obviously it's not necessary.
This is one of the polish chips. I had to take a picture because it looked so pretty!