Q: What kinds of finishes can you apply?
A: Water based polyurethanes, oil based poly, epoxy, conversion varnish, shellacs, lacquer, varnish. We can spray most finishes (this makes for a better quality finish). We use more traditional finishes as appropriate.
Q: What is conversion varnish?
A: Conversion varnish is similar to the paints used in the auto industry. It is a catalyzed finish, which means a catalyst (or hardener) is added to it, this limits the time the finish can be applied before it hardens. Once sprayed it cures to a working point in less than an hour, and can be resprayed with in 2 hours. It is one of the most durable of finishes, virtually impervious to alcohol and water. It requires more work to repair and is a costlier finish, in addition to being a bit more finicky to apply. It takes a week or so after application to thoroughly harden and be ready for full use.
Catalyzed finishes are usually more difficult to apply and clean up, and in some cases to cure/harden (epoxy for example, due to the length of time). Professional grade flooring products (not what you can buy from Lowes or Home Depot) are another example of a catalyzed finish. They can be water or oil based.
Q: Why not use a polyurethane?
A: Polyurethanes are a great finish, but have their own unique qualities. Water based poly is reasonably durable, applies relatively easily, but requires a thick layer of finish. In some cases that may not give the desired impact. Water based poly out of the can is what the finishes industry calls ‘water white’ — it leaves a clear coat when it hardens. It can be colored/dyed to resemble the effects of oil based poly; there is at least one brand that makes a line specifically for that reason. Water based poly also raises the grain when it is applied. This requires more sanding during the finishing process.
Oil based poly is more durable, requires chemicals to clean it up and will out gas while drying. It adds an amber affect to the wood it is applied to. The final finish is also usually thinner, which in some cases is important.
Q: What is a ‘flattening agent’?
A: A flattening agent is added to a finish to create the various levels of shine or reflection in a finish: sheen. In a clear finish it is the cloudy material at the bottom of the can.
From Sherwin-Williams: Gloss and sheen reflectance are measured on a scale of 0 (no gloss) to 100 (mirror-like). Reflectance is typically measured by deflecting a single beam of light at a 60 or 85 degree angle off a surface. The light is deflected into a receptor, which measures the intensity in units. The higher the number of units, the shinier the surface.
A low sheen doesn’t mean the surface can’t have a polished surface, though polishing it will raise the sheen at least a bit.
It is important to apply the final coat in the sheen that is required. Applying it in lower coats will mute the depth of the finish and make it appear murky/opaque. Tthat may be acceptable or even intentional. When possible, the lower coats should be gloss coats.
Q: Why do I care about UV protection? When should it be used?
A: UV protection must be used when a product will have more than a casual exposure to direct sunlight. It makes the finish more expensive, but it will last much longer and will slow down changes in color.
Q: Wait a minute — changes in color will only be slowed down?
A: All woods change color with exposure to light. Woods that are stained will change some, depending on the degree the stain has changed the base color of the wood. Woods that are lightly stained, not stained, or exposed to a lot of light will change the most. In addition, many species are particularly light/UV sensitive. One of the most common species is cherry. It will darken over time, usually most obviously in the first 6 months. It can be stained to look darker at install, but it’s hard to say to what degree (or speed of change) their will be over time. Other woods tend to change color, such as many red, purple, and orange colors, etc. Most will darken.
Q: What about stains?
A: Stains come in three main variations: oil, water, and gel. Oil takes longer to dry, but doesn’t raise the grain in the wood. It requires chemicals to clean up, and takes longer to dry. Water based stains dry fairly quickly, but raise the grain when applied; this requires extra effort to sand the finish off to remove the raised grain. Gel stains are used most often for two different reasons: on closed grained wood, often due to conditioner use; or to re-stain a surface to a different color (without stripping the surface). As a gel, it can be left on a surface for a longer period with out running off or drying out.
Q. What are closed cell woods? Why do they need to be treated differently?
A: Closed cell woods tend to have a ‘blotchy’ look when stained — if they have not had a conditioner applied. Sometimes that’s okay, sometimes it is not. Closed cell woods include: pine, spruce, maple, cherry. If you look closely at the wood, the cellular openings are much smaller than open celled woods. Common species of open cell woods include oak, walnut, mahogany. If you look at a finished piece of these woods with the light reflecting off of the wood you can see how smooth the closed cell type are, and how there are little dashes on the surfaces of the open celled wood. A wood conditioner is usually a thinned clear coat product, or a specialized product just for this purpose. Shellac, lacquer, polyurethane are common choices. Open celled woods can have the pores filled for a smoother surface; see below.
Q: I understand that you can’t mix oil and water based finishes?
A: Not true. You can’t mix finish layers that are not hard. For example, latex paint has latex (or similar performing products) in it. Latex is what rubber is based on. It never quite hardens, at least in this context. Most oil and water based products we might use will harden. As long as the finish is hard/dry/catalyzed, it can be coated with out worry. There are finishes that require intermediate coats of other products, but that has much more to do with the way thinners and the chemistry of bonding occur. For most concerns, the oil/water based controversy relates to stains and clear finishes.
Q: Can you color the wood or fill voids? Fill pores?
A: Yes. There are a number of methods that can be used to color woods. Two different dyes can be used, a pigment dye, or a stain dye. Pigments leave tiny little pieces in the wood, and tend to highlight grain or other details (such as distressing). Stain dyes are more like food coloring, they change the color in general. They can be used together. Additional affects can come by using grain fillers (for open pore woods) that are a different color. Epoxy can be colored, including with a glow in the dark agent, to fill voids or strengthen/stabilize a weak area in material. In the case of clear/opaque applications, objects can be included (such as stones, badges, or momentos).
Q: What is milk paint?
A: Milk paint is made from, well, milk. Way back when you didn’t go to a store for everything (not because you didn’t want to — you just couldn’t take the time, nor always had the money; other paints, like lead based, really put out a great look and lasted a long time). You made what you needed when you could. Milk paint is a very durable paint, though it also leaves a rough/grainy texture and has visible brush strokes. This is often desirable, especially for a worn or antiqued look. At least one brand has a line of acrylic paint marketed as milk paint (it dosn’t look very milk paint like to me, but is still good paint). Milk paint should be refrigerated if it isn’t used up on the day it is mixed. It usually leaves a flat sheen surface, but a sealer can be applied with varying degrees of gloss (you get most of the affects of milk paint, but easier to clean). Due to the flat finish, the colors tend to be deeper. Glazes applied to the rough texture also highlight the depth of the paint.
Q. What finishes are safe to use around my children or around my food?
A. All current finishes that are cured/hard are safe for use in food based areas, including children’s products. That may take a lot longer than expected — as much as a month for the final cure. Some finishes are ready to use very quickly; they usually require regular maintenance. Such as walnut oil, mineral oil, or beeswax. These are often used for cutting boards; where surfaces are subject to sharp damaging use, just about any finish would fail due to ‘death by a thousand cuts’. Oils that do not go rancid are a better choice. As long as you are willing to maintain them, oils & waxes are good choices.