When I was using S500, I had foaming issues and was told to add calcium carbonate (I think that's what it was. ) an anti foaming agent put out by Hangsterfers. Worked for about a day and we were back to mopping the floor...
Went to Neo Sol 300 at the Hangsterfers rep's recomendation and have been happy since. We cut a lot of stainless and this works well.