Bentonite is only used if polymer is floating during application, it serves as sinking agent - but does nothing to help promote a seal otherwise. We have only used bentonite in response to floating polymer in 5% of projects, if that many. But it's something I mention "just in case" so the pond owner is aware and prepared to address float issues during application.

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

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