What's in dough?

I was very interested to read the letter 'Playdough anyone?' (25 September). Like Jane Mills, I have always made the playdough using the cooked method, and usually without any problem. I have followed the same recipe, same method, same products, and same quantities for years. We always keep it in an airtight container, and find it will last a good half-term. However, also like Jane, recently I started having identical problems with my playdough and tried the same ways she did to solve them, but without success. At the pre-school we wondered if the manufacturers had altered or added different...