Tuesday, December 9, 2008

How to finish wood with stain and a polyurethane finish

Finishing wood can be a tricky and complicated process that stresses out even the best woodworker. Stains and polyurethane finishes often look great and can protect your wood project for a long time. If you take this process slow, pay attention to every detail, and follow these steps exactly, you will soon forget what all the fuss was about when it comes to finishing up our wood projects.

The first procedure of a good finish starts with surface preparation. Plane the surface until the surface is free of defects and uniform if you are working with a rough-sawn piece of wood. Your local lumber store can do this for you. take care to remove all glue marks and scratches, as common stains will highlight these defects.

Use Medium Grit Sandpaper
Now we are going to take a medium-grit (120-150 grit) sandpaper, and lightly sand the surface of the entire wood project. When sanding, you want to be sure to sand in the direction of the woodgrain. Always use a fresh piece of sandpaper, and avoid using old pieces of paper. Make about two or three passes with the medium grit sandpaper.

Use 220 Grit Sandpaper
Once the project has completely sanded using the medium grit sandpaper, it is a good idea to go over the entire project again with a finer grit (180-220) sandpaper. Make two or three passes over the entire project.

Brush your work
Use a soft nylon dusting brush to wipe off the entire surface area of your wood project. You do not want to leave any dust on the surface of your project.

Use a Tack Cloth
Now take out your tack cloth and wipe down the surface of the entire project to avoid any small dust particles sticking to the surface.

Stain A Testing Board
Great job so far. I know that you are eager to crack out your stain, sealer, or poly and start applying coats to your wood project, but you need to restrain yourself and create a testing board to see how the stain and finish is going to look on your project. THIS IS A VERY IMPORTANT STEP THAT YOU SHOULD NOT SKIP - AS IT HELPS TO SHOW YOU WHAT YOUR FINISHED PRODUCT WILL LOOK LIKE. Get out a 2 foot board or so of scrap wood from the project you created. Divide it up into four or five square sections to test coats of your stain, poly, or sanding techniques. The picture I found on Google gives a good idea how to divide the boar, but you can experiment and do this however you want. I recommend that you divide the wood into a "raw wood section", a "sanded wood section", a "stained wood section", and a "finished" section with your final sealer. With this sample piece you can test different stains and finishes to see how the project will appear when complete. It is also used to test any finishing technique deviations before applying them to the project.

On your testing board, use a lint-free cotton cloth and wipe a generous amount of stain onto the wood in the "stained wood section" and let this dry. If it looks the way that you envisioned, then let it dry and apply your poly finish to make sure that everything looks good. If you like the results, move on to the next step. If you want it darker, add more stain, lighter, get a lighter shade of stain and retest.

Apply Stain with a lint-free cloth
When you are happy with the results of the stain, use your lint-free cotton rag and apply a base coat of your stain onto you sanded wood project. Work the entire surface of your project with the stain.

Once the entire project is coated in your stain, take a clean lint-free rag and wipe off any excess. Let this coat dry thoroughly- it might take about 2 hours or so to dry, so check back often on the finish. You know when it is dry because you will be able to touch the surface and feel a smooth clean surface, instead of a tacky, sticky surface. If you touch your stain and it leaves your fingerprint, then it is too wet. Do not worry if you leave a print, because we are going to sand this coat in the next step.

Take your 220 grit sandpaper and very lightly, dry sand over your entire finish. The purpose of sanding between coats is to remove any large irregularities and to make the finish level. Look for bubbles, smudges, glue marks, finger prints, or dark blotchy areas in the stain. As the finish is built up, the grit number of the abrasives used between coats is increased, or it gets finer.

Wipe your entire project clean again with your brush and your tack cloth to remove any dust particles. Add more coats of stain until you reach the color and depth that you want. As each coat dries, gently sand in between coats like you did in Step 10.

In this next step, you can skip it if you want, but if you want an extremely smooth finish, I recommend that you use synthetic steel wool ( not real steel wool as it very abrasive) and gently wipe down the entire surface of your project to get a more uniform surface without any scratches made by the sandpaper. This step will also help to provide a better surface for the following finish layer.

Now that you have finished staining and sanding your project, you will want to apply your water-based polyurethane. Take a wide foam brush and apply a thin coat of the polyurethane in the direction of the grain of the wood. Cover your entire project with one thin coat.

Let the polyurethane coat dry for two to three hours and then sand it lightly with the 220-grit sandpaper. You want to be careful to very lightly sand this coat, as you do not want to go through it to the stained coat underneath - you just want to smooth out an imperfections in this coat.

Again, wipe your entire project down with the tack cloth and your dust brush to remove any particles of dust.

Repeat the process of applying a thin coat of polyurethane. This will be coat two. Let this dry for two to three hours, and lightly sand it again with 220 Grit sandpaper.

Apply a third and final thin coat of the polyurethane, and let it dry. No sanding this time - YOU ARE DONE!

It is not a necessity that you use the same finish technique or product on the entire project. For example, assume you chose Danish oil as the primary finish for a chest of drawers. You may use polyurethane or acrylic for the drawer boxes, interior parts, or the applied back. This would save a great deal of time and effort.

If you are working with a film type finish and you want a satin sheen, apply the gloss version of the product as a base, then apply the satin sheen as your last coat. Do this for as many layers as you need, but always apply the satin finish last. The reason for this is that a satin finish defracts light, and you do not want to build up layer after layer of satin coats - it makes your final finish look muddy.

When working with water-based polyurethane and a large area that needs to be finished, use a paint pad to apply the pol urethane. The reason for this is that water-based polyurethane dries quickly and applying it with a brush will not allow you to cover the area adequately.

Do not apply any stains or finishes in direct sunlight.

If the finish has not dried thoroughly it will ball up on the sandpaper when you go to sand it. If this is the case, allow the finish to dry for a few more hours. Once dry, sand out the irregularities and continue to follow the staining and sanding process.

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