There's nothing to fear from water that would already be in there from being on the shelf. As endlessness observed, that would migrate to the base layer.
However, a small amount of water from the base layer will still be present in your naptha after you separate it. This presents a problem, as base water in your solvent means residual hydroxides. Hence the traces of lye that end up in peoples' spice.
There is a method of dealing with this that involved drying the np solvent by using baked epsom salts. One bakes the epsom salts in the oven at 400 degrees, then powders the salt and adds it to the np solvent. The salts will clump up as they absorb moisture. Lack of clumping indicates all the water has been absorbed.
Do this following a brine wash (washing the solvent with a few ml of water that has been made basic with something like sodium bicarbonate, calcium carbonate, ammonium hydroxide, etc. so that it will remove NaOH but won't pull too much spice) to obtain an ultra-pure spicey goodness, only where legal of course.