On Tue, 07 Oct 2008 08:33:12 +0100, Jane Gillett
> wrote:

>I suggest what
>happened with the onions may have been polymerisation - you formed a type
>of plastic which was resistant to water and detergents and that's why you
>couldn't remove it.

You have the problem to a tee! And, probably, the only thing that will
shift that now is methylene chloride.