This whole discussion is -AGAIN!- a microcosm of what has been plaguing our yiddishkeit, (and some of the comments on this website) in recent years. Not one of the posters can muster even ONE credible argument why playdough should be ossur and needs a hechsher. The fact that one baby actually ate it and survived does not make it “ro-ui leachilas kelev”. No sensible adult (or dog) would eat it.
Additionally,as indicated by Itzik, cream of tartar routinely is considered kosher.
On top of that, the “cheshash” of making a table top treif (!!!) is such an unusual idea that you don’t need too many reasons to make it “mutter”.
Yet, squeak questions even these very simple sources and wants us to be “machmir”. WHY?
This is in line with the “machmerization’ of our yiddishkeit-contrary to all of our halachic principles over the centuries.