Nail Polishes can dry caused by evaporation when the bottle is left open or not tightly closed. But also during a long manicure process the Polish might be exposed to the air too long causing the fluid to dry out and thicken.
I have lots of nail polish that is getting thick, few drops does the trick. 123
It only took a couple drops for even my most dry, goopy, nail polish. I used it on a very old base coat and the base coat still dried really quick. 123
I found that quite a few drops were required to thin out my polish. A few drops won't do the job. Otherwise this product left my polish in good quality and still kept it's shine. I always worry that the polish will be dull and have a different texture. Not the case with this! 123