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Not everything has to have a furniture finish.
IIf you read woodworking magazines or look online, you often come across instructions for plumping pores, veiling, toning, scrubbing, and so on. These are wonderful techniques to use on sophisticated projects like furniture. But they are often overkill for basic kitchen or bathroom cabinets.
So it can be useful to divide the finish into two categories: for furniture and for furniture. This article describes the simplest cabinet finish. It involves only three – maybe four – steps: preparing the wood, sealing, finishing and sometimes coloring.
Preparation of the wood
Preparing wood for a finish involves sanding, removing dents, filling gouges, and dealing with glue leaks, which can cause a lighter colored finish or stain to appear.
The goal of sanding is to remove milling marks caused by machining and other defects. You just need enough sand to achieve this. Sanding can be done with stationary or manual power tools or manually. Whichever method is used, the steps are the same.
Start with a sandpaper grit that removes defects efficiently without creating larger sanding scratches than necessary. Then work through the grits, making the scratches smaller and smaller until they are no longer visible after coloring or finishing. In most cases, you would start with # 80 or # 100 grit and work up to roughly # 180 grit. The finer grit you use should always go with the grit to help mask any remaining scratches.
Dents can often be vaporized by dripping water into the depression and touching it with a hot object such as a soldering iron to turn the water into steam.
Gouges cannot be steamed away because part of the wood is missing. Then fill them with solvent or water based wood putty. Colored wood fillers are available in wood tones, which you can use to more closely match the final color.
Glue leaks must be removed or they will hinder the penetration of the stain or finish and affect the color. To reduce glue seepage, apply less glue to the joints and keep your hands clean.
Remove the glue leaks by washing off the still wet glue or waiting for the glue to start to solidify, then lift it with a spatula. If you applied a stain before noticing the problem, sand or scrape off the glue, then wet sand the entire area with more stain to help with the stain as well.
With dents, gouges and glue seepage repairs, you need to sand again with at least the finest grit to level the repair or remove the raised grit.
The sealing is obtained with the first coat. This can be the finish itself or a separate product used to solve a problem. Whatever you use, you should sand this first coat to create a smooth surface under subsequent coats.
Use sanding sealer to make sanding easier, except for oil-based or water-based polyurethane finishes because these finishes are fairly easy to sand down on their own.
Shellac is often mentioned as a sealant, but is only needed when trying to block a problem in wood, such as silicone oil, smoke odors or animal urine, or natural oily resin in many exotic woods. Shellac is a useful sealant when refinishing, but is rarely needed when refining new wood.
The finish is crucial because it is the layer that provides the most protection against moisture (very important in kitchens and bathrooms) and durability against scratches and heat. It also provides the shine (glossy, satin or flat) and part of the coloring. For the overcoat you will probably choose from the following:
■ Oil-based polyurethane is among the most durable and water resistant finishes. It dries slowly, so it’s easy to brush. It gives the wood a slight yellow-orange color.
■ Water-based polyurethanes and acrylic finishes are sufficiently durable and water resistant, but less so than oil-based polyurethane. Neither adds much color, so these are good choices for light woods like maple and ash when you want to keep the natural color. The first coat, while being easy to sand, raises the grain more than solvent-based finishes.
■ Nitrocellulose and cab-acrylic paints dry quickly and are sprayed. Both are less protective and durable than polyurethanes, but are easy to use if you have a spray gun.
■ Pre- and post-cured lacquers and paints are as durable as polyurethane and dry quickly, then sprayed.
■ Shellac is similar to nitrocellulose paint in terms of scratch and water resistance.
■ Oil finishes are too thin and soft to work well on kitchen and bathroom cabinets.
The most common mistake made in paint cabinets, whatever finish used, and especially when spraying, is not coating door edges well enough. A thin finish in these places is quickly broken by the water. Pay particular attention to edges and all three-dimensional surfaces, such as embossed panels.
The stain is applied before sealing to add decoration to the wood, but it also increases the likelihood of problems, including the following:
■ The stain is usually caused by irregularities in the wood. For the pine, use a gel stain to avoid the problem. For hardwoods prone to stains such as birch and cherry, apply a wash coat (the finish diluted with 3-10 parts thinner) and allow to dry completely before staining.
■ Darkened head grain is mainly the result of inadequate sanding. The still rough surface retains more stains when the excess is removed. A washcoat will also help with coloring and will also stiffen the wood fibers for easier sanding. You can use a rag or brush to target the washcoat on the final grain only.
■ Poor adhesion is often caused by not cleaning the excess stain. The stain has much less binder than paint, so it separates when bumped.
■ Poor adhesion can also be caused by applying a water-based finish to an oil-based stain before it has completely dried.
Whatever finish or procedure you use, it’s best to test on scrap wood before committing to a full set of cabinets.
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