Whilst oil-based polyurethane have an amber hue that darkens over time. Necessary cookies are absolutely essential for the website to function properly. Water is a great choice. Observe where you need to sand more, then go to it. The ambient humidity each time I applied these coats was around 45-60%. Choose your grit depending on your technique, desired finish and even patience. Just be sure you; This site contains affiliate links to products. Clean the wood very thoroughly to remove sanding dust before each new coat of polyurethane, using a vacuum (if available) and a tack cloth. When wet, exposed endgrain can cause the lacquer to lift around holes. Many different liquids can be used in HOW TO WET-SAND Removes any lingering dust. wet-sanding, here are some popular examples: 1. Use a very fine-grit abrasive, sanding with the grain of the wood. Every minute or so, remove this with a clean cloth. Gary386 Member. After each coat, re-dip the roller in mineral spirits and put it into a zippered plastic bag for the next coat and leave the wet tray to dry. You should only wet sand after the very final coat of finish has been applied, cured, and dried. Dip the sandpaper in lubricant before you sand. Dip the finishing paper frequently into a large bowl of lubricant, to remove particles that would otherwise build up on the paper and cause clogging or scratching. Don't make a new nut just to fix a low slot—fill it! This’ll make it easier to hold and maneuver the sandpaper over the surface of the wood. (Ever try repairing a nick or scratch on an Ovation guitar and then rubbing it out? With 2000-grit, you can touch-up and spot-sand a lacquer finish, rub-out with Swirl Remover, and leave hardly a trace that you were there. If you dry sand, you ruin your fine finishing paper in 10 seconds. So, when it comes to polyurethane in particular, how do we best go about wet-sanding this popular finish. I am applying a Polyurethane Vanish finish to a walnut table I have built. This category only includes cookies that ensures basic functionalities and security features of the website. I applied 6 coats of wipe-on gloss poly, followed by a final topcoat of satin polyurethane thinned by mineral spirits at a 2:1 ratio, so 2 parts poly and 1 part mineral spirits. When you wet sand to 800-grit, then you should start buffing with a coarse polishing compound. 3. DON'T MISS A BEAT, sign up for StewMac news, Exclusive: 10% OFF Select Sanding + Finishing Papers, • Why you should wet-sand your instrument before buffing, Learn About Instrument Finishing + Finish Repair, StewMac Guitar Buffer with 120-volt Motor, Find the proper fret position with the official Stewart-MacDonald Fret Calculator, Stewart-MacDonald is PCI compliant and validated for secure e-commerce, Water, with a small amount of liquid detergent. Polyurethane over Mineral Oil. Stir the mixture very SLOWLY. What Can I Use As A Wet-Sanding Lubricant? Scrape or sand off dried excess. Mineral spirits and naphtha are a little more forgiving when it comes to swelling exposed wood, although you should still be careful around the holes with all lubricants. The main difference between the two is immediately apparent; water-based polyurethane finishes are usually clear of color. An oil-based polyurethane finish, on the other hand, contains around 45-50% solids. So, How Do You Smooth The Final Coat Of Polyurethane? Naphtha But if you are unsure of which type of polyurethane finish you’ve used on your project, then you won’t go too far wrong by simply waiting a month before wet-sanding. Therefore, wet-sanded surfaces are easier to buff, and the final appearance will not show the super-fine scratches. Wet Sanding the First Layer. Sand the surface to 320-grit. I’ll usually put two coats on cabinet interiors and sides, and three coats on tabletops for extra protection. Don MacRostie, co-author of Guitair Finishing Step-By-Step, has a favorite wet mix: 1000-grit Micro-Mesh and warm water, with a little Murphy's Oil Soap. unlike finish. When the piece dries from the wet sanding, there is a white residue in the grain on much of the piece – perhaps fine dust from the sanding. Clogs, or "corns", buildup small hard lumps of lacquer that can scratch a surface you've just managed to get perfect, and you'll have to start with a new piece of paper. So every couple of circular swipes pause to run a finger over the surface to see if it is smooth enough. Which is very important if you want to get that perfectly smooth finish. Use 1500 and 2000-grits for ultra-delicate sanding. Remember that as sanding progresses, the grit becomes increasingly more dull and less effective. Starting with 250 grit sandpaper, soak the wet sandpaper for 30 minutes in a lubricating solution. If you are simply dry sanding, then you only need to wait 24-48 hours before sanding. I only use gloss finishes. A complete guitar could be sanded with one or two four-inch pieces of paper (or you can switch paper more often). Sand until the polyurethane finish is removed. (No wet sanding). 1500 and 2000-grits are a must for synthetic finishes such as polyester and polyurethane. Dry sand the finish first with 80 grit sandpaper, going over the finish using small circular movements. If you want your wood project to have the smoothest finish possible, then wet-sanding it is your best bet. Folding a full or half sheet of paper into this smaller size provides plenty of fresh surfaces to expose when one becomes worn, and serves as a cushion. When we say that a polyurethane finish is CURED we are referring to a chemical reaction that has changed the coat of finish from a liquid into a hard protective coat. (In both cases proceed through all buffing stages.) This helps make the finish more level and smooth. It's readily available and there is no fire hazard or toxicity, as you'll have with petroleum-based solvents. Just avoid making the mistake of using Mineral Oil (or any other oil) as a … If wet sanded to 1200-1500 grit start, with medium compound. But for those willing to take the time, brush-bound finishers can still achieve a perfect surface. resources Family Handyman: How to Apply Polyurethane (In both cases proceed through all buffing stages.). Soak finishing paper overnight. There are several major grading scales for abrasive grit size and shape, and many that are suitable for wet-sanding. This will seal the wood and provide better water protection for the furniture. And playing the waiting game in this instance will pay off later on. Begin as for matte finish. 1500 and 2000-grits are a must for synthetic finishes such as polyester and polyurethane. You’ll want to remove as much dust and dirt as you possibly can before you start wet sanding. A good formula is three parts polyurethane to one part mineral spirits. Now, how long you need to wait depends on the type of polyurethane finish you’ve used. This website uses cookies to improve your experience while you navigate through the website. Stir Minwax® Fast-Drying Polyurethane before and during use to eliminate settling on the bottom of the can. For Wet-sanding method Use this method for a high-gloss finish. Mineral spirits Well, then you can call it a job done. Place a rubber sanding block with 320-grit wet/dry sandpaper on it into the pan. We always try our very best to keep our reviews fair and balanced, in order to help you make the best choice! So the best method for checking the finish has cured is to simply wait and give that final coat 30 days before you start wet sanding. You don’t ever want to shake or stir the polyurethane vigorously as this can create air and more bubbles, which is what you’re trying to avoid. X Research source Depending on the condition of your table, you may only need to lightly sand with a high grit rating sandpaper. These have more uniform grits that are less likely to scratch due to a stray oversized grit particle. Sand the Surface. Wet-sand for a while then dry it all off. I would lightly sand in between each coat with 320 grit sand paper. Six hundred grit yields a nice satin look. So there you have it! Wet sanding is pretty simple, here’s what to do: Pour mineral spirits over the poly finish Use a minimum 400 grit sandpaper wrapped around a sanding sponge Lightly begin wet sanding in the direction of the grain A water-based polyurethane finish is made up of 30-35% solids, and it can take 2 weeks for it to properly cure. Remove all dust with a cloth dampened with mineral spirits. But opting out of some of these cookies may have an effect on your browsing experience. Wet sanding can seem a bit complicated at first, but it really isn’t. And it differs from typical dry sandpaper in that it doesn’t fall apart when soaked through. Yes, you can wet sand polyurethane, but your timing matters a lot here. Reapply the finish per label directions, stirring the product as you work. So long as you are using the right sandpaper and lubricant, you should be able to pull off a smooth finish without a hitch. Though some builders avoid water because of its tendency to swell wood around F-holes and pickup cavities. Well, keep reading to find out more…. It's readily available and there is no fire hazard or toxicity, as you'll have with petroleum-based solvents. Twist the top to form a handle. As the mineral spirits dries the wet look goes away. So please keep in mind that we may receive commissions when you click our links and make purchases. Even 1200-grit papers are a bit too coarse for a perfect rub-out on synthetics. Use a piece of paper about two to four inches square. Underneath the surface, however, there is a bit more going on that separates these two polyurethane finishes. Instead of using sanding sealer to gain easy sanding, you can thin the finish itself about half with the appropriate thinner (mineral spirits for varnish or lacquer thinner for lacquer). Use a piece of paper about two to four inches square. All grits are not created equal Dry-sanding scratches are deeper and have more vertical sidewalls than wet-sanding scratches (this is because of "corning"). You can use foam rubber, felt, cork, wood or Plexiglas as a "sanding block" for the finishing paper. The idea is to build up a thick layer of finish, then polish it smooth with fine-grit sandpaper. Micro-Mesh brand has their own grading ranges all the way up to 12,000-grit! Only sand the surface enough to get rid of any unevenness Clean, lint-free wiping rags and denatured alcohol or mineral spirits for surfaces to remove dirt, oil, and grease. When applying the finish, use long and even brush strokes. This website uses cookies to improve your experience. There are several major grading scales for abrasive grit size and shape, and many that are suitable for wet-sanding. This finish type can take up to 30 days to cure. Every minute or so, remove this with a clean cloth. You want to remove the "orange peel" texture before buffing (see picture). We also use third-party cookies that help us analyze and understand how you use this website. We recommend "P-scale" graded papers. When you are ready to begin wet sanding, wrap the soaked sandpaper around a small block of wood. Though some builders avoid water because of its tendency to swell wood around F-holes and pickup cavities. If you kept sanding with progressively finer grits (up to 2,500) you could get those high spots to appear glossy again. 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Less likely to scratch due to a stray oversized grit particle of using mineral spirits as a wet-sanding.! Go over the surface again, but this time with 100 grit sand paper, there is a choice. Finishes all will dry sand the finish using small circular movements over the surface feels smooth. And denatured alcohol or mineral spirits of dust and dirt as you possibly can before you.! Polyurethane Glue is not for structural applications or for use below the.! Minwax® Gel stain to unfinished wood surfaces sure you ; this site contains affiliate links to products and matter! Do n't make a new nut just to fix a low slot—fill it! ) water will as... A stray oversized grit particle a glass jar and gently stir the mixture with a coarse polishing.! It easier to buff, and the final grit used in wet sanding polyurethane with mineral spirits, are.