Boy, oh boy, I can't wait to see the Google search that leads people to this posting.
Have you ever brought a bottle of polish home thinking you have this awesome bottle of polish only to find out that the color is so sheer that you need 7 coats just to get the color of the bottle? The opacity of many polishes will clearly be evident. However, if you pick up a bottle and are unsure, just check its balls.
The little steel mixing balls of course! Now, obviously, if your polish doesn't have the mixing balls, well, you're out of luck. However, it if does, hold the bottle up to check 'em out. With opaque polishes you will only see the little dot of the ball. Check out the pictures:
Looking at the two bottles above (China Glaze Mediterranean Charm on top and Zoya Jenine, yes I bought it just for the name, on the bottom), all you see are little dots. This are nice and opaque polishes, see:
If you hold the bottle up and you can pretty much see the entire ball, you've got a sheer polish on your hands here:
With these two polishes, you can pretty much see the entire ball. Both of these polishes (Butter London Disco Biscuit on top and Revlon Grapefruit Fizz on the bottom), while pretty, are quite sheer.
These are both 3 coats of polish, and you can see how sheer the polishes are.
Now, granted, the opaque polishes I picked are pretty obvious, as are the sheer ones. But I have put down bottles based on the ball trick (one being a Deborah Lippmann, which is a brand that I love, but I wanted the color to be opaque, and it was just too sheer). As a rule, I just don't like sheer polishes, I'm way too anal about a visible nail line to futz with sheer polishes, and I never have luck with underwear polishes, I usually just avoid them. I did willingly buy Disco Biscuit after the ball trick because I just simply loved the color and couldn't resist.
I may be stating the obvious here, a thing that everyone knew and I'm last to the table, but just in case I'm not last - I'll repost it for those that are!
Between balls, anal and underwear, this blog is probably going to be placed on interesting lists. Weeeee....