I haven't come across its use for a garden pond but bentonite-enhanced soils
are used extensively as liners for landfills - they can deliver very low
permeabilities without the need for a plastic liner. A landfill needs pretty
thick clay (about 1 metre) and special plant to compact it, which wouldn't
be much use to you, but there again you are not building a landfill and
don't need such low permeability. A much thinner layer should work well
enough for a pond. You mustn't let it dry out, though. Presumably the people
who sell the bentonite provide instructions?

Let us know how you get on.

Peter

"Nicholas Walker" wrote in message
...
Thanks to those kind helpers.

Research has revealed the existence of Sodium Bentonite powder and
"BentoMat" membrane, which is Bentonite sandwiched between a geosynthetic
layer.

Does anyone have any experience of these products?

Haven't found a UK price yet but the stuff reads like a real cure-all

Blocks all leaks, natural product, self-sealing, natural-looking

Many thanks again

Nick Walker