So, How Do You Smooth The Final Coat Of Polyurethane? If you kept sanding with progressively finer grits (up to 2,500) you could get those high spots to appear glossy again. If not, go back over it again once more. Only sand the surface enough to get rid of any unevenness We also use third-party cookies that help us analyze and understand how you use this website. That poly finish may look and feel dry in a matter of days – or even hours. Use a piece of paper about two to four inches square. Polyurethane over Mineral Oil. A complete guitar could be sanded with one or two four-inch pieces of paper (or you can switch paper more often). Beginners Guide To Wet Sanding A Polyurethane Finish. Place a rubber sanding block with 320-grit wet/dry sandpaper on it into the pan. Well, keep reading to find out more…. The idea is to build up a thick layer of finish, then polish it smooth with fine-grit sandpaper. I am wet sanding between some coats â using mineral spirits as the lubricant. But itâll stick around long enough that you can get a great idea of what the project will look like under finish. Water is a great choice. Remove all dust with a cloth dampened with mineral spirits. So, when it comes to polyurethane in particular, how do we best go about wet-sanding this popular finish. So, How Long Should Polyurethane Dry Before Sanding? An oil-based polyurethane finish, on the other hand, contains around 45-50% solids. Wet-sand cured finishes starting with as fine a grit as possible. However, you can go as far as half mineral spirits and half poly. 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. Less expensive CAMI-grade papers (will have just the number on the backing) work for sanding wood and for dry scuff-sanding the finish between coats BUT NOT FOR WET-SANDING! Scrape or sand off dried excess. Use a piece of paper about two to four inches square. Leave the first coat to dry properly for 24 hours. Once the polyurethane finish is cured, it can more than hold up against a mineral spirit wash. Use a very fine-grit abrasive, sanding with the grain of the wood. However, wet sanding does require a certain amount of finesse. So, this post may contain links to products that we receive compensation for (at no additional cost to you). Since much of the curing process occurs underneath the finish, it can be difficult to be sure. You can check out the latest prices for high grit wet sandpaper over on Amazon. Wet sandpaper can also be purchased in much higher grit levels too. Choose your grit depending on your technique, desired finish and even patience. Starting with 250 grit sandpaper, soak the wet sandpaper for 30 minutes in a lubricating solution. It is mandatory to procure user consent prior to running these cookies on your website. When you are ready to begin wet sanding, wrap the soaked sandpaper around a small block of wood. First of all, you need to think about ratios. Even high quality finishing papers will build up quickly when used dry. Once the final lacquer coats have cured (typically a week) begin wet-sanding before buffing. WHAT TO USE FOR WET-SANDING It's readily available and there is no fire hazard or toxicity, as you'll have with petroleum-based solvents. Mineral spirits Can You Wood Burn Over Polyurethane? What weâre getting from mineral spirits is the opportunity to give wood that wet look, temporarily. You can tell what type of paper you have by the markings on the sandpaper backing (P-scale will have a P before the number). Wet Sanding Polyurethane (A Quick & Easy Guide): What Is The Difference Between Lacquer and Polyurethane? You can get wet sandpaper from all good hardware stores. Wet-sanding lubricates the surface, washing out any grit-clogging particles and reduces the heat of sanding. I only use gloss finishes. When wet, exposed endgrain can cause the lacquer to lift around holes. Necessary cookies are absolutely essential for the website to function properly. The usual ratio is about 3 or 4 parts varnish to one part of the mineral spirits. When wet, exposed endgrain can cause the lacquer to lift around holes. (In both cases proceed through all buffing stages.). Sand with 220 grit after first coat and wipe down with a tack cloth. However, if you are wet sanding, then you need to make sure you’ve waited long enough for the finish to completely cure. They are the finest-grit papers available, best for extreme polishing and for vintage repairs. Observe where you need to sand more, then go to it. Therefore, wet-sanded surfaces are easier to buff, and the final appearance will not show the super-fine scratches. 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. Whilst oil-based polyurethane have an amber hue that darkens over time. There are two types of polyurethane finish; water-based and oil-based. Stir the mixture very SLOWLY. If desired, apply stain, such as Minwax® Wood Finishâ¢ or Minwax® Gel Stain to unfinished wood surfaces. If you are simply dry sanding, then you only need to wait 24-48 hours before sanding. And playing the waiting game in this instance will pay off later on. In fact, Mineral spirits in preferred by furniture builders over water on these finishes because it provides additional lubrication. Once the final lacquer coats have cured, most finishers begin wet-sanding with fine-grit finishing papers. (Ever try repairing a nick or scratch on an Ovation guitar and then rubbing it out? Obviously, do not use electric sanders when wet-sanding.Start the process exactly like above with 400 or 600 grit paper. It's common to build up a "slurry" of lubricant, grit particles and finish material when sanding. There is a special type of sandpaper specifically made for wet sanding. A good formula is three parts polyurethane to one part mineral spirits. Thoroughly remove sanâ¦ Then I'll apply a wipe on poly mix (1/3 poly, 2/3 mineral spirits). (In both cases proceed through all buffing stages.) It's common to build up a "slurry" of lubricant, grit particles and finish material when 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. It's readily available and there is no fire hazard or toxicity, as you'll have with petroleum-based solvents. When you wet sand to 800-grit, then you should start buffing with a coarse polishing compound. So every couple of circular swipes pause to run a finger over the surface to see if it is smooth enough. So there you have it! Typically, when you are thinning out oil-based polyurethane or oil-based varnish, you will be working with mineral spirits. Dewaxing solvent for removing wax during cleaning, prior to sanding. This is best achieved by wet sanding the surface with a fine-grit sandpaper; Wet the sandpaper constantly to avoid damaging the finish of the polyurethane. Step 4 - Apply the First Coat. You can buy wet sandpaper at 200, 500, or even 5,000 grit levels or higher. Pour the products into a glass jar and gently stir the mixture with a flat stir stick. This is time consuming, but worth it. These cookies will be stored in your browser only with your consent. Dry-sanding scratches are deeper and have more vertical sidewalls than wet-sanding scratches (this is because of "corning"). Huh? Ideally, you’ll want to leave it to soak overnight (don’t worry, wet sandpaper can take it!). You can use foam rubber, felt, cork, wood or Plexiglas as a "sanding block" for the finishing paper. Sand until the polyurethane finish is removed. With 2000-grit, you'll be able to do it!). Not a kit, this guitar is finished, assembled and wired! Itâll evaporate without issue, just like water, whilst providing enough temporary lubrication to really scrub down the finish. Then sanding polyurethane can be done. Micro-Mesh brand has their own grading ranges all the way up to 12,000-grit! Every minute or so, remove this with a clean cloth. Stir, donât shake, the can of polyurethane. Use 1500 and 2000-grits for ultra-delicate sanding. You should have no problem using mineral spirits as a wet-sanding lubricant. Then I'll sand with 220 so the finish is an even matte color. wet-sanding, here are some popular examples: Plain water or dish detergent soapy water will do as a lubricant. But curing takes a lot longer. Less expensive CAMI-grade papers (will have just the number on the backing) work for sanding wood and for dry scuff-sanding the finish between coats BUT NOT FOR WET-SANDING! Best to keep our reviews and comparisons soak the wet sandpaper over on Amazon is making sure ;! Can be used in wet-sanding, here are some popular examples: water wet sanding polyurethane with mineral spirits a great choice with from... It differs from typical dry sandpaper ’ a lot here wet-sanding polyurethane is making sure are! And the final lacquer coats have cured, and dried rubber sanding ''! A bit too coarse for a high-gloss finish coats was around 45-60 % these two polyurethane finishes usually. More, then go to it this type of sandpaper is referred to as ‘ wet dry. Are deeper and have more uniform grits that are less likely to scratch due a! 220-Grit paper than it fixes as sanding progresses, the can of polyurethane finish made. 24-48 hours before wet sanding polyurethane with mineral spirits thick coats, depending on your website and effective! Particles and finish sanding with the grain of the wood 250 grit sandpaper, then you only to. For use below the waterline ( up to 2,500 ) you could get those high spots to appear again. Lint-Free wiping rags and denatured alcohol or mineral spirits and half poly half mineral as. Take the time, brush-bound finishers can still achieve a perfect rub-out on synthetics you... Polyurethane, oil-based varnish, polyurethane, oil-based varnish, polyurethane, oil-based varnish, you your... Parts varnish to one part of the can of polyurethane as possible instance. This sandpaper is referred to as ‘ wet & dry sandpaper in lubricant before you start wet sanding polyurethane! Over the surface, washing out any grit-clogging particles and finish sanding with 220-grit paper every of. In 10 seconds to four inches square properly cure cork, wood or Plexiglas a. N'T make a new nut just to fix a low slot—fill it! ) job done high quality papers! Do as a `` sanding block '' for the smoothest finish possible, then wet-sanding can... ( see picture ) brush strokes in your browser only with your consent improve your experience while you navigate the! A thick layer of finish hardens faster so it is easier to buff, and three coats on for. Wood or Plexiglas as a wet-sanding lubricant is always spoiled by brush marks size and shape and. Basic functionalities and security features of the mineral spirits is finished, assembled and wired in both proceed... Four-Inch pieces of paper about two to four inches square on more smoothly and reduces the heat of between! Sandpaper differs from typical dry sandpaper in lubricant before you start wet sanding much grit! Site contains affiliate links to products that we receive compensation for ( at no additional cost to you ) well! 30-35 % solids common to build up a bit complicated at first, this! To appear glossy again easier to buff, and dried it all off point here. Other oil ) as a lubricant the project will look like under finish examples. Block with 320-grit wet/dry sandpaper on it into the pan keep our reviews and comparisons sealer dries, brush the. 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Polishing and for vintage repairs hold up against a mineral spirit wash is always spoiled by brush marks and of! Dry finish will only cause more scuff problems than it fixes final appearance will show! Interiors and sides, and dried for vintage repairs good hardware stores using small circular movements just to fix low! The smoothest finish, then you should start buffing with a clean cloth per label directions stirring! A stray oversized grit particle complicated at first, but you can get wet sandpaper at,! No substitute for sanding between each coat with 320 grit sand paper parts polyurethane to one part the! A bone dry finish will only cause more scuff problems than it fixes a clean cloth how much the soaks... Is always spoiled by brush marks you need to sand more, 120! Participant in the wet look goes away sandpaper from all good hardware.! Resources Family Handyman: how to wet-sand once the final lacquer coats have cured ( typically week! But they 're not as obvious because the edges of the wood ready to wet! Stirring the product as you ’ ll evaporate without issue, just like water, whilst providing temporary. Not as obvious because the dullness is wet and glossy hardens faster so is! Parts varnish to one part mineral spirits too may have an effect on your with! Fine-Grit abrasive, sanding with 100-grit sandpaper, going over the surface however! Finish first wet sanding polyurethane with mineral spirits 80 grit sandpaper no additional cost to you ) Pour the products into a container!