I have experimented with creating nail polish several times; always using eye shadow pigment for the color. It is a great way to customize your own color. The results are a metallic, glittery creation; made by you. I have only used two eye shadow pigments to try this: NYX Ultra Pearl Mania in Mink Pearl (a rose gold/coppery shade) and Lancome Loose Powder Eye Shadow in #04 (a yellow gold shade with a lot of pigmentation.)
DIY Nail Polish
I do not have a set formula for creating nail polish because how much clear polish you add depends on the material you are working with.
The Lancome pigment eye shadow requires more clear polish or it will be too thick to apply & it dries more quickly than the NYX shadow. This is by no means a difficult process. How much pigment and clear polish you use depends on how much you are making; how many coats you want to apply.
With the NYX pigment eye shadow, 1/16-1/8 tsp of shadow and around 15-20 drops of polish equate to one coat of polish for both hands. With the Lancome, you would be better off using less shadow & polish and making two small batches because it dries so quickly.
Creating your own nail polish is easy & fun. I even tried out a couple of glitter top coats for extra oomph. I used Sinful Colors “Glass Pink” (a sheer micro-glittery baby pink shade) and OPI “Let’s Do Anything We Want” (a multi-colored pink/white glitter/confetti top coat from the Disney Muppet’s Most Wanted Collection.)