Vermiculite and Gypsum

I see Homebase are selling Vermiculite, this used to be used a packing and insulation, but is very good for starting runner beans and the like, as it encourages root growth, stores moisture and allows the plants to be taken out without damaging the roots. Now for a piece of chemistry; clay needs an something ionic to break its colloidal structure down. Lime can be used but it tends to make the soil alkaline, In cases when the soil needs to acidic, such as a lawn, then Gypsum(Calcium Sulphate)can be just as effective. S**** plasterboard, but not old plaster as this can be lime plaster, is a cheap source or it can bought in a garden supplies shop.