Polycrylic is one of the new breeds of water-based clear coats on the market. It’s an excellent product that offers many benefits, yet some of those benefits can make it tricky to apply without knowing a few tips.
Regular readers will know that I have over 40 years of making every mistake possible in woodworking. High on the list of these errors is blundering into paint or surface finish applications without understanding the little idiosyncrasies of the product I’m using. I was always wise after the event.
To prevent you from following my example, I want to share some of the issues you’ll encounter applying polycrylic. A streaky finish is one problem people encounter, for which there can be several causes. Accompany me for the next two minutes, and I’ll step you through tips to improve your chances of a quality finish.
What is Minwax Polycrylic?
Minwax Polycrylic is a water-based polyurethane designed for interior use over bare wood, wood stains, paints, and wallpaper. Unlike some other polyurethane products, it has a low odor, is non-flammable, and requires only soap and water for cleanup. One of the key benefits of polycrylic is that it dries very quickly. The name polycrylic is a brand name registered by an architectural coatings manufacturer called Minwax.
- PROTECT WOOD SURFACES – Minwax Polycrylic Protective Finish protects and adds beauty to your interior wood projects, including woodwork, furniture, doors and cabinets. The clear top coat protects...
- CRYSTAL CLEAR FINISH THAT LASTS – The crystal clear finished offered in this protective coating is ideal for use over all Minwax Oil-Based and Water-Based Stains and colors, as well as all wood...
- SATIN SHEEN – Give your wood projects a sleek finish with a satin clear varnish. It not only protects the natural beauty of the wood, but offers an attractive, classic sheen for a modern and subtle...
Polycrylic and polyurethane: are they the same?
Yes, they are. Polyurethane is a generic name for a mix of urethane resins held in suspension in a carrier liquid. While some polyurethanes use oil-based carrier liquid and others use water-based, the same principles apply. The carrier liquid assists the application of the resins by brush or roller, then evaporates, leaving the resins behind to harden on contact with air.
While each manufacturer will use a different recipe of additives and flatteners to make its product, the essential features of polycrylic and polyurethane are the same. Polycrylic is a brand-name polyurethane that uses a water-based carrier, which dries quickly and has less odor than oil-based polyurethane.
What is the best way to apply polycrylic?
Minwax recommends using a high-quality synthetic bristle brush. Be sure to choose a brush with very fine bristles and a soft tip for best results. While you might choose to use a roller, you will usually end up with air bubbles and streaking, so I don’t recommend it.
How to apply polycrylic without streaks and brush marks
Here are some steps to follow to give yourself the best chance of applying polycrylic without streaks or brush marks.
Tools and supplies
Step-by-step Polycrylic application instructions
- Ensure you have adequate ventilation in the room. While polycrylic has a low odor, the fumes will irritate your respiratory system if inhaled. Wear a painter’s mask if you have concerns. Always wear gloves.
- Prepare and clean the surface you wish to coat with polycrylic. Clean the surface with soap and water and dry thoroughly. If it’s bare wood or painted wood, lightly scuff with 220-grit sandpaper to level the surface and create a keying surface for the polyurethane. If you’re covering wood stain or wallpaper, do not sand but ensure the surface is clean.
- Vacuum the surface to remove all traces of airborne particles and sanding dust. Finally, wipe the surface with a painter’s tack cloth to remove any last traces of contamination.
- Carefuly open the tin without shaking. This step is one of the stages where, if you’re not careful, you can trap air into the liquid or cause streaking, so open the tin of polycrylic without shaking it or inverting it, and stir it gently but thoroughly with your paint stirrer. If you don’t stir the polycrylic well, you can end up with a streaky or inconsistent finish as some of the heavier solids have not evenly dispersed through the liquid. Don’t worry that the polycrylic looks white in the tin; it dries clear.
- Dip the brush in Polycrylic. First, wet your brush in water, squeeze out the excess and then dip the first half to one inch of the brush into the polycrylic. Do not wipe the brush on the side of the tin to remove excess liquid, as this traps air in the bristles. Hold the brush over the surface of the liquid until the excess has drained, then move to the next step.
- Apply Polycrylic over the surface. Using light strokes, begin to apply the polycrylic to the surface. Use only the first half-inch of the brush and angle the brush 10 to 15 degrees in the direction of the stroke, applying the coating in the direction of the wood grain.
- Work one small area at a time. Polycrylic dries extremely rapidly, and if you try to cover too large an area, when you come back to where you started, you’ll be applying wet polycrylic over a dry edge. If this happens, you risk getting banding or streaking.
- Don’t overwork an area with repeated brush strokes. As the product dries so quickly, you can end up leaving brush marks on the surface. You’ll also introduce air and get bubbles in your finish. Gently and smoothly apply the coat in one or two strokes and move on.
- Allow the first layer of Polycrylic to dry. Clean the brush with soap and warm water while allowing the first coat to dry. MinWax recommends a minimum drying time of two hours.
- Sand the surface. Once the first layer has dried, lightly sand the surface with 220-grit sandpaper to smooth the finish and create a slightly rough surface to allow the next coat to adhere properly.
- Vacuum the surface. Vacuuming is important to remove all traces of sanding dust, and wipe the surface with a painter’s tack cloth.
- Apply additional coats as in steps five through eleven. Do not sand the surface once you’ve applied the third and final coat.
- Allow the last coat to dry. Leave the finished object for at least three hours before gently handling it. Do not subject the item to normal use for 24 hours.
How many coats of polycrylic to apply?
Minwax recommends a minimum of three coats of polycrylic for most interior uses. As polycrylic is water-based and quite thin, there is no limit to the number of coats you can apply as there is with oil-based polyurethane. However, if you apply too many coats over a very dark surface, you may get a milky, streaky look to the finish. I’d stick to three coats to be sure.
Do you have to sand polycrylic between coats?
Yes, Minwax recommends you do. Sanding serves two purposes, it smooths any brush marks, bubbles, and blemishes, while creating a lightly abraded surface to allow the next coat to stick.
Don’t apply too much pressure when sanding, as you don’t need to take off everything you’ve just applied. Be sure to clean up well afterward; otherwise, you’ll have all that sanding residue stuck in your finish.
How long to wait between coats?
There’s no maximum time, only a minimum. The polycrylic should be dry, which takes at least two hours, possibly three. Be aware that the drying time will extend if the ambient temperature is colder than 77oF or damper than 50% relative humidity. Allow three to four hours to be sure.
Do you have to sand the final coat?
No, you don’t. If you’ve been careful to follow all the steps, your finish should be good. However, you can buff or polish the last coat of polyurethane to level out any small brush marks and raise the sheen a little, but it’s not necessary for most jobs.
How long does polycrylic take to dry?
Each coat should be left to dry for a minimum of two hours before applying the next coat. The last coat should be left for 24 hours before the item is subjected to normal use. Full cure of the polycrylic will occur when the polyurethane has reached its maximum hardness, which occurs after 21 to 30 days.
How to avoid bubbles when applying polycrylic
There are five occasions when air can become entrapped in the polyurethane and cause bubbles in the finish. Your careful attention to these five points maximizes the chance of getting a high-quality finish.
- When handling the tin of polycrylic, do not shake or invert the tin. Doing so aerates the liquid, and when you brush it on, the bubbles surface and create a rough, unpleasant surface.
- Stirring the polycrylic gently but thoroughly is important. Too rough, and you introduce air. Avoid stirring, and you don’t distribute the flatteners and other additives evenly through the liquid. In each case, the surface finish will be sub-standard.
- Before loading the brush with polycrylic, wet the brush with water and gently squeeze out the excess from handle to tip. The water displaces much of the air trapped in the bristles that would otherwise transfer to the polyurethane when applied.
- When loading the brush with polycrylic, dip only the tip of the brush into the liquid, to a depth of half to one inch. Then lift the brush and allow the excess to drain naturally. Wiping the brush on the side or lip of the tin introduces air to the polycrylic, which will cause bubbles when applied to your work surface.
- When applying the polycrylic, use gentle flowing motions and use only the tip of the brush. Be sure to angle the brush’s handle by 10 to 15 degrees in the direction of travel. Don’t go over and over the same surface multiple times; apply the coat and leave it. Overworking an area introduces air and can leave brush strokes.
How to get bubbles out of polycrylic
It’s not uncommon to get the odd bubble, no matter how diligent you’ve been during application. If the polycrylic is still wet, you use the very tip of the brush for popping the bubbles and lightly brushing over where they were.
If the polycrylic has dried, wait 2 hours and then lightly sand with 220-grit sandpaper to take the tops off the bubbles and smooth the finish. Remove all traces of dust with a painter’s tack cloth before applying another light coat of polycrylic over the top.
Related: How to Fix Polyurethane Mistakes
Can you use polycrylic over paint?
Yes, you can. It doesn’t matter what type of paint it is; just be sure it’s fully dry before following the steps given above.
When to apply polycrylic after painting?
The key to getting good adhesion between the polyurethane and paint is to ensure the paint is truly dry. Paint and polyurethane manufacturers differentiate between dry times for recoating and dry times for top coating.
I’d wait 12 to 24 hours before applying polycrylic over oil-based paint and 8 to 12 hours for water-based paints. You’ll read of people who have done it within 2 hours for a water-based paint – they got lucky. I see no sense in ruining a long and expensive job for the sake of a few hours. Save yourself some grief and apply the polycrylic the next day.
Related: How to Apply Polyurethane over Paint
Minwax Polycrylic FAQ
Can you apply polycrylic over chalk paint?
Yes, you can. Once the chalk paint is fully dry, follow the steps above for applying polycrylic.
Will polycrylic affect the color of paint?
In most cases, polycrylic dries clear and does not affect the underlying paint. However, be careful when applying it over dark colors. If you apply too many coats or the coats are too heavy, you can see a milky finish. This phenomenon is not the underlying paint but the polycrylic itself.
Can polycrylic be used over stain?
Yes, it can. Allow the stain to dry fully before applying the polycrylic. Do not sand the stain before application, as you may lift some of the stain and get an uneven finish. Just ensure the surface is clean and dust-free before following the application steps given above.
How long does polycrylic take to cure?
Polycrylic has the same cure time as all polyurethanes. Full cure will occur within 21 to 30 days.
Will polycrylic turn yellow over time?
No. Polycrylic is a water-based polyurethane that dries clear. Unlike oil-based polyurethanes that have an amber tint and yellow with age, polycrylic will retain its clarity.
Final word on Minwax Polycrylic
While polycrylic is easy to apply, it’s less easy to apply while achieving a quality finish. Part of the reason is its rapid dry time, which can cause banding, streaking, and brush marks. The other reason is that all polyurethanes are susceptible to entrapping air and creating bubbles on the finished surface.
However, if you have patience and carefully follow the steps given in this article, you have a fighting chance of achieving a finish to make you proud. I trust this information has been useful, and I wish you good luck with your project.