Re: Japan Drier?
I haven't used it , but suspect it will work. Maybe mix just a little and try it on a scrap of wood. Assuming you are talking just standard one part polyurethane.
However, the question needs to be asked why you are using spar varnish on the floor. Spar varnish tends to be softer and more flexible for the bending of the spar. It seems you want a hard polyurethane for the floor.
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