Is play-doh kosher for Pesach? If not, can it be used after Pesach if I mevatel it with the rest of my chametz or does it just need to be thrown out (and re-bought each year)?
Play-doh (plasticine) is not kosher for Pesach, in the sense that it is made with flour and water, and it must not be eaten.
However, there is no problem of keeping it over Pesach, and its halachah is similar to the halachah of a “chair made of chametz,” that was specified for sitting on, which can be kept in one’s possession over Pesach.
Just like the “chametz chair” is a chair, and not food, and therefore does not constitute a problem of keeping it over Pesach, so too play-doh is not food — even though it is made edible so that it won’t cause damage to children.
If children might come to eat it, it should not be given to them to play with over Pesach.