Remove any old paint, varnish, or other finishes before applying the polyurethane topcoat for the best results. You'll want the surface of the wood to be as smooth as possible for a smooth coating, so sand it with a sanding block or orbital sander. You can also use fine-grit and medium-grit sandpaper to get the job done.
After sanding, wipe off the wood with a damp cloth to remove any dust. Now is a good time to apply a coat of polyurethane if your project doesn't require super-shiney conditions. You can let it dry overnight and then re-apply if needed. If you want to get an extra-deep shine, you can follow up the polyurethane with another coat of polish.
Painting after polyurethane gives the finished product more life, but not all paints are compatible with polyurethane. Read the packaging carefully to know what types of materials are used in the product and whether that will affect how you finish your project.
Even so, I still recommend sanding between coats of polyurethane to assist promote adhesion between the layers and give you a more even surface. The more even the surface, the less likely you are to get spots where the finish will not cure all the way around an object.
The best tool for this job is a fine-tooth sandpaper pad that can be bought in a pack of 100 pads. These come in different sizes from 150mm to 400mm and are available at hardware stores. They are useful for getting into small holes and cracks in surfaces.
You should use a paper towel or two under the sandpaper pad to prevent sanding marks on your woodwork. Then repeat the process with a finer grade of sandpaper if needed.
It's important to wear protective clothing when sanding polyurethane because it is very sharp and can cause skin problems if it gets into your eyes or on your hands. Also, keep out of reach of children.
Polyurethane needs to be sealed before you paint it to improve durability. There are several products on the market that claim to do this job well. I've had good results using Woodlife's Polyurethane Sealing System.
How to Make a Polyurethane Matte Finish
When it's completely dried, sand it again until the surface is smooth. Make certain that the rough surfaces are evened out. Unless you prime your polyurethane-treated furniture, your paint will not adhere effectively. Because other types of paint primers are incompatible with a polyurethane finish, an oil-based primer is your best alternative. The best time to apply an oil-based primer is before you stain or paint your wood furniture. This will help the final product go on more smoothly and prevent any cracks from forming due to moisture changes when you stipple the paint later.
If you want to change the color of your polyurethane-treated furniture, first mix a small amount of paint in a spray bottle for light colors or a large barrel for dark colors. If you want to add depth instead, try mixing different colors of paint or using a tint or shade. You can also use a pre-mixed primer called "polyurethane furniture paint". This product comes in several colors and usually gives you better coverage than applying a single coat of paint. Be sure to follow the instructions on the container about how many coats to apply.
Polyurethane-treated furniture should never be stained or painted with water-based products such as water-based paints or wood stains. These products will eventually eat away at the finish over time. Instead, use oil-based products such as olive oil, walnut oil, or mineral spirits to protect your investment.
A single or two coats of polyurethane applied to a painted surface is an effective approach to protect the paint. Although it takes many hours longer to cure, oil-based polyurethane levels out to a smoother surface. Polyurethane may be applied over any sort of paint as long as it is clean and properly prepared. If the original paint is not removed first, then additional coats may be needed in several years.
The choice of materials should match your project requirements. For example, if you want a durable finish that will stand up to moisture, use acrylic polyurethane. If you just need something that will give protection while keeping out insects, use vinyl polyurethane. Both are easy to apply and can be bought ready-to-use. There are also products available that combine latex and oil-based polymers for added protection. These can be thickened with solvents or water for custom colors.
Polyurethane comes in a variety of forms including spray, powder, roll-on, and foam. Each one has its advantages depending on how you plan to apply it. For example, spray polyurethane goes on fast and is very flexible. It's best for small projects. Powder polyurethane is more durable than spray polyurethane and can be used on larger surfaces. Roll-on polyurethane is similar to paint in how it is applied but it has a thicker formula and tends to get darker over time.
While staining produces a rich, deep color that accentuates natural wood grain, it does not give long-term protection. Wood is readily harmed when it comes into touch with water, food, or sharp objects if it does not have a protective top layer. A top coat of polyurethane protects the wood from scratches, stains, and water damage. When applying a top coat, be sure to follow the instructions on the package for proper curing time.
Allow your paint to completely dry. To gently scuff and flatten the paint, lightly sand it using 120 grit sandpaper. Before applying your finish, be certain that all dust has been removed. If you are refinishing a previously waxed object, you must first remove the wax before applying your polyurethane. Use a clean soft brush to gently sweep away any powdery residue left over from the wax.
Now that your surface is ready, apply a thin even coat of polyurethane using a foam roller. Let it sit for at least 30 minutes until hardened. You can speed up this process by heating your polyurethane, but this is not recommended unless you want to change the color of your finish.
Heated surfaces are usually yellow or orange due to the presence of ultraviolet light absorbers in most polyurethanes. These chemicals are used to prevent sunlight-induced degradation of the polymer. Heating causes these compounds to evaporate into the air, leaving less than desirable colors in their place. The heat also affects other parts of the material, such as its color or hardness, which should be taken into account when choosing heating methods.
The best way to apply polyurethane is with a sprayer. This will give you a very even coat with no patches where it was missed. Make sure that you follow the instructions on your sprayer about how much product to use and how often to spray for optimal results.