Did you know that if you wanted to ‘thicken up’ some Chalk Paint ™ from Annie Sloan you can just leave the lid off the pot overnight. Or a speedier alternative is to keep the lid on, and place in a fridge for about 2 hours, crazy eh! (the exact timing depends how thick the paint is to start with).
To get it back to how it was, just add back a little water, or add even more to get a good ‘wash’ effect.