To restore thick polish, use Restoration Drops, our KBShimmer polish thinner. For thickened polish, start with 2-3 drops, shake, and check consistency. Repeat until you are happy with the result. For dried out or severely thickened polish, fill the bottle with thinner to the fill line, let it sit overnight, and shake in the morning. As always, we highly suggest cleaning the necks of the polish bottles after use to allow a good seal to reduce polish evaporation in the long run.