provent a mite question

[Domepiece]

Why would it dry on a substrate and not a tub? That makes absolutely zero sense. Treating tubs is not a problem, just don't spray too heavily or from too close up to the enclosure.

It makes plenty sense. It seems to be an oil based product and if sprayed on the tub it will leave an oily film, if sprayed on substrate it absorbs into the substrate. It will dry on both obviously but if it doesnt have a substance or material to absorb into it will just sit on the surface as an oily film which technically speaking is not dry. There is a specific reason why the manufacturer explicitly say on the directions not to spray directly onto the enclosure.