For lawns that puddle after rain and then set hard. A litre of liquid gypsum supplies calcium and sulphur, which is what helps a dispersed clay hold together as crumbs rather than slump; 500ml of the natural wetting agent lowers the surface tension of the water carrying it, so it goes down through the thatch instead of sitting on top or running off.
That pairing is the reason the two are here together: the wetting agent is not doing anything to the soil chemistry, it is getting the gypsum to where it is needed.
Worth being plain about the limits. This helps a clay soil that disperses. It will not drain a lawn sitting on a high water table or over a pan that needs breaking mechanically, and it is not a substitute for aeration where the compaction is physical. Each product carries its own application rate.
