If you are sanding between polyurethane coats, always ensure that you use sandpaper of a very fine grit. Always allow polyurethane to dry 24 to 48 hours before sanding, to give the surface time to cure and harden. Sanding Polyurethane Between Coats. A dry coat of poly is around 0.003” thick, and the grains on 220 sandpaper are 0.0045”. Sanding Polyurethane Between Coats (image source) Stain or No Stain. You will get oil-based and water-based polyurethane in the market. Realistically, dry sanding polyurethane at any grit can potentially leave a scuffed looking cloudy surface. Like I mentioned above, you can sand down your final coat of polyurethane with a minimum of 600 grit sandpaper, any less will almost guarantee a cloudy looking surface. While not necessary, Polyurethane for Floors can be sanded between coats for maximum smoothness. If you rush it or live in the tropics with hi humidity, you get these waxy boogers of poly instead of nice milky poly dust when sanding between coats. Before starting, you need to make sure you have decided about the type of polyurethane that you are going to use on your hardwood floor. 400 or Scotchbrite between coats, and just enough to rough it up so the next coat sticks. If you do stain, you don’t want to sand after the stain application, before the first coat of polyurethane. You should ensure that you sand the previous coats so that you create a perfectly level and even base for your final coat. Then just wipe off the dust with mineral spirits and apply another coat. Allow for a minimum polyurethane dry time of 24 to 48 hours before applying the next coat. Think about it this way. Do You Sand the Final Coat of Polyurethane? I lightly sand between coats with extra-fine synthetic sanding pads. Pro Tip: If there are stubborn nibs that stand up to the pads, grab 280-grit and be more aggressive. No, you are not supposed to sand the final coat. When applying polyurethane, brush along the grain, stretching the polyurethane into as thin a coat as possible. That is why, if you do not want to apply polyurethane coats, again and again, sanding between different layers is … The reasons you may need to sand between coats are to "de nib", that is to take off dust specs and knock the tops off any bubbles in the finish. In a nutshell, it significantly increases the efficiency of polyurethane coats. Instead, it would be best if you sprayed it or spread it in a nice and level way. A light sanding between coats is necessary only if Polyurethane for Floors has been allowed to dry for 12 hours or more. If you want a natural wood finish, you can skip the stain. The goal is to roughen the surface a bit and rub out dust motes, hairs and drips. This is an area where 'prevention is … Allow the finish to dry 4-6 hours before sanding. Dry Sanding The Final Coat of Polyurethane Finish. You can also sand to take care of drips etc., but proper application technique should avoid those. It really doesn’t take much to sand right through, particularly on outside corners. Sand Between Coats of Polyurethane – on Floor & Wood Furniture: What type of product do I need to use? Sanding Between Coats of Polyurethane. The longer you wait, the more the grain raises and the finish cures. Furthermore, do you have to sand between coats of polyurethane on floors? You will need a more thorough sanding for glossy finishes than with semi-gloss or satin finishes. Apply two to three additional coats of full-strength polyurethane, sanding between each coat. Sanding Between Coats by Alan Noel Professional Wood Finisher When applying several coats of finish to a project it becomes necessary to sand between coats to not only remove any trash that has settled into the finish but also to promote good adhesion between the layers of finish. So you had better sand to promote adhesion best also. As you can see, sanding in between coats of polyurethane has numerous benefits. You don’t have to stain before you use polyurethane.