Finishing Touch: Staining
All wood species are beautiful in their own right, but not all are perfect when it comes to woodworking, materially or aesthetically. Sometimes they need a little pick-me-up. At the lumber yard, it can be difficult to get boards that match reasonably well in grain and color. It’s not uncommon to end up with boards that aren’t harmonious in appearance – for example, with too much sapwood in a field of otherwise-darker heartwood. Or, while your heart might be set on walnut or mahogany, your budget might limit you to alder or red oak. Sometimes though, you just want to add a splash of colour to a project, regardless of the wood you’re using. In cases like this you can choose to colour the wood to even out those variations, to mimic the appearance of a different species, or to walk a bit on the wild side. Staining is a way of doing this.
In a broad sense, a stain is any liquid that contains a colouring agent (aka ‘colourant’). This can be a pigment, a dye, or a combination of the two. Pigments are finely ground, insoluble natural or synthetic materials that are suspended in a binder (such as linseed oil, varnish or lacquer) that bonds the pigment to the wood. A carrier (such as mineral spirits or water) spreads the pigment and binder over the wood surface. Pigments remain on the surface of wood, lodged in pores and surface scratches, which makes them good for highlighting surface textures. However, many pigment stains will also contain some dye, so that the stain delivers a more intense colour with less obstruction of the grain pattern. You’ll know that the product you have is a pigment stain if the contents settle to the bottom of the can. This is why you want to thoroughly stir the contents before applying the stain – so that the pigment is dispersed throughout the liquid. Most often, stains that contain pigments (or a blend of pigments and dyes) are simply referred to as ‘stains’, and they’re available as ‘oil-based’ or ‘water-based’.
Dyes, on the other hand, are soluble chemical substances that do not require a binder. They come in either a liquid or powder form, though they’re rarely available at hardware or home improvement stores. In the liquid form they never contain any pigment, which is why you don’t get any goop at the bottom of the container. Dyes saturate wood fibres, giving a more uniform colour to wood (which is why they’re often added to pigment stains). We’ll look at dye stains in an upcoming article.
Stir it Up
Before stirring most stains the product will separate, leaving a thinner liquid on the top (Up). Once the stain has been stirred it will look richer, and be a bit thicker (Down). You will feel the sediment on the bottom of the can when you start stirring.
Gel stain is very thick. Because of this, it tends to not penetrate into the wood. It remains on the woods’ surface, where it more evenly colours the wood.
How Many Coats?
Here, Duguay stained an oak sample once, then taped the left half of the sample off, and stained it again. The wood is darker with two coats of stain. There are diminishing effects as you apply more and more coats.
When working with blotchy woods, like cherry, maple and pine, using a wood conditioner will even out stain penetration, and leave you with a more uniform look.
More Sanding, Less Absorption
Duguay sanded the face grain of this sample to 150 grit, and the end grain to 600 grit. The higher sanding grit lessened the end grains ability to absorb the stain, and therefore creates a more even look.
What’s in a Name?
This douglas fir sample was stained with four different stains, though they were all called “cherry”.
Oil, water and gel
The stains that you do get at your local hardware or home improvement store come in three types: as a free-flowing liquid that is either oil based or water based, and as a gel that is oil based. Most manufacturers offer products in all three formats.
Oil-based stains (sometimes referred to as penetrating stains or wiping stains) are probably the most popular type. They’re easy to apply, especially on large surfaces, as they don’t dry out too quickly. On open-grained wood you’ll see a more dramatic result – the stain will darken the grain but leave the wood surface lighter in colour. Close-grained woods accept stain more evenly, resulting in a more uniform colour. Leaving the stain on longer before wiping it off will allow more of the carrier to evaporate, resulting in a more intense colour. As well, you can apply a second coat of stain to increase the colour intensity.
Water-based stains are less odorous, less toxic, and easier to clean up than oil-based stains. However, they do dry faster, making them more difficult to apply over large surfaces. Also, they raise the grain, so you want to dampen the wood and then lightly sand it before applying the stain. For anyone who works in a small shop with less-than-optimal ventilation, they’re a better choice than oil-based stains.
Gel stains are the consistency of peanut butter. Because they don’t run, they’re ideal for use on vertical surfaces and where you have a lot of narrow edges and crevices, as well as on carvings and turned items. They’re also the best choice to use on blotch-prone woods (see below).
In general, any topcoat will go over any of these stains. However, it’s important to ensure that the stain is completely dry before top coating. You can get stains that contain both the stain and a topcoat all in one can, such as Varthane’s One Step Stain & Polyurethane (a water-based formulation) and Minwax’s PolyShades (oil-based). They’re applied in much the same way as a conventional stain, though they dry faster than oil-only stains.
Any of these three types of stain will deliver great results as long as you apply them in the right way. If you’re new to wood finishing you might want to test all three. This will enable you to choose the one you find easiest to use. Most are available in 236 ml cans. Select the same colour for all three types of stain, and apply them to cut-offs of solid wood and plywood, then once dry, lay on your favourite topcoat. As with most things, a modicum of practice will help you refine your staining skills.
It’s all in the sanding
The key to achieving a great stained finish is how well you prepare the surfaces before applying the stain and topcoat. Make sure that you do a final sanding by hand, in the direction of the grain. Shine a light across the surface of the wood at a 45° angle – it will help you see any imperfections that need attending to. It’s important to remove excess glue completely, particularly around joints. On coarser, open-grained species (like ash or oak) you can sand up to 180- or 220-grit, but on close, tight-grained species (such as maple and cherry) sand up to 120- or 150-grit. If you sand these woods too smooth they’ll have difficulty absorbing the stain.
Stains can be applied with a paintbrush, foam brush, by rag, or spray. Liquid stains dry fairly quickly, so it’s best to heed Mr. Miyagi’s advice to ‘wipe-on, wipeoff ’ in quick succession. On large surfaces you want to maintain a wet edge, to avoid lap marks. If they do occur, lay on a second coat of stain after the first one has dried. Of course, the best way to avoid this problem is to spray on the stain, though this is really only efficient if you have a lot of square footage to cover.
Not all wood is the same
Different wood species will stain differently, and even boards of the same species may take stain quite differently. The grain pattern that each board exhibits, the presence of sapwood and heartwood, the way that the boards were milled (quarter sawn, flat sawn or rift sawn), and even the relative humidity level in your shop will have an impact on the final look.
As well, woodworkers often use the same wood species in both a solid wood form and as a plywood. Cabinet sides, shelves and doors are often made of plywood, with the framing done in solid wood. Typically any exposed edges of plywood are covered with solid wood edging. This can pose a problem when applying a stain, especially if you use low grade plywood, which tend to have very thin veneer. The discrepancy is much less evident when you use good quality cabinet grade plywood (or shop made ply). Options to deal with this include applying a wood conditioner, using a gel stain, or applying a second (or third) coat of stain to the plywood to darken it sufficiently to match the solid wood. Invariably though, you’ll need to go through some trial and error first.
Some woods blotch
Some woods, such as pine, cherry, maple, and birch, are blotch prone – they absorb stain unevenly. There are two options to deal with woods like this. I’ve had pretty good success using gel stains. Because they’re thicker, they don’t penetrate wood grain as much as oil- or water-based stains. A second option is to apply a wood conditioner before staining – there are different conditioners for oil- and water-based stains. The wood conditioner will help the wood absorb the stain more evenly. Be generous with the conditioner, and remember to wipe it off before it dries on the wood. Once dried, lightly sand. Optionally you can apply a thin coat of shellac, though I’ve found that this results in a lighter colour once the stain is applied.
Take care of the ends when sanding
Pay special attention to end grain. The deep open pores provide cavities for the stain to lodge in, which is why end grain usually stains darker than face or edge grain. You can resolve this by sanding the end grain much smoother (which burnishes the pores and reduces their ability to absorb stain), or applying a wood conditioner, or you can do both.
Not all colours are the same
It’s good practice not to mix stain brands or types on your project. A cherry stain from one manufacturer won’t necessarily look the same as the same cherry stain from a different manufacturer. Nor will an oil-based cherry stain look the same as a water-based or gel cherry stain. If you don’t like surprises, test any new stain before using it. Make sample boards (from cut-offs of the solid wood and plywood from the project) to test the stain that you plan to use. If you anticipate using the same species of wood and colour of stain again, you might want to record details on the back of the sample boards and retain them for future reference. It’s very discouraging to discover that the stain you just applied to a finished project is much too dark. You’ll have to sand down to bare wood in order to apply a lighter stain (or live with the darker stain).
Create your own custom colours for staining
Most of the time you’ll likely want to purchase an ‘on the shelf ’ colour and use it for your project, but if you’re the adventurous type, you can create your own custom colours by intermixing stains of the same type (just don’t mix oil- and water-based stains). You’ll need to do some testing to tweak the right colour, so start with measured small amounts (say, 15 to 20 mL). Keep track of the amount and ratio you use so that you can then blend larger volumes of the custom stain for your project.