We know what blotchy means…patchy, covered with blotches, uneven, spotty. When it comes to woodworking, we know also that we don’t like blotchy finishes. A spotty and uneven finish on our project almost takes the fun out of woodworking after cutting, sanding, assembling, choosing a stain color, and everything we put into our project.
However, it also presents us with an opportunity to learn and recover. Stuff happens, and while we get upset for a few minutes, we vow to find a solution. When we have, and the project still ends up turning out well, we regain that sense of satisfaction from our work.
Sometimes we get an uneven finish with our stain application, and the wood grain becomes more pronounced in color than the surrounding wood, something we did not want. It’s not the end of the world, and it can be fixed. We’ll spend some time today discussing this and pointing you in the right direction.
Wood stains are a type of paint that is used to add color to wood and enhance the appearance of the wood grain. It is composed of a colorant and a medium into which the colorant is dissolved or suspended. The medium, also referred to as the “vehicle,” may be water or oil, and while the results of application may be the same, there are some differences.
The difference between wood stain and paint is that paint will lie on the wood surface, whereas stain will actually penetrate the wood and is absorbed by it. Staining your project will seal the pores and act as a barrier to water. Stain will not waterproof the wood, but it does inhibit the absorption of water.
Stain has 4 main ingredients: the colorant (pigment), the vehicle (volatiles), resins, and additives. The volatile, that which the other ingredients are dissolved or suspended, will evaporate as the stain dries after application and leave the color behind.
With a consistency of a thin oil or a water-based paint, they can be applied with a brush (bristle or foam) or a cloth, with any excess stain not fully absorbed into the wood pores wiped away after a short period of time. Failing to wipe off excess stain can mean an uneven or blotchy finish.
Types of Wood Stains
There are several types of wood stains available for your project finish, and there are enough differences among them to have some influence on the choice you will make among the type of stain chosen.
Water-based stains. The water is the vehicle, or volatile, the medium in which the colorant (pigment) has been dissolved or suspended. It’s easy to apply, is resistant to mold and mildew, and cleans up easily. It is, after all, water-based, and a little warm water and soap will clean your hands and brush. It also dries quickly and won’t slow down your project. A second coat, if necessary, can be added the same day, as it dries that quickly.
Oil-based stains. Oil is the volatile, the medium in which the pigment and additives are dissolved or suspended. They have very good adhesion and will penetrate the wood just below the surface. Oil-based stains, though, contain chemicals that require some extra steps not necessary with a water-based stain. These chemicals and the VOCs (volatile organic compounds) can be harmful, and a respirator should be worn when applying this stain.
The room where you are working with an oil-based stain should be well-ventilated, too, with good air circulation. Even after the stain has dried, the chemicals and VOCs will linger in the air, so precautions should be taken. It takes much longer to dry than a water-based stain, and you won’t get a second coat in the same day unless you start very early and the environment is highly conducive to a quicker dry.
Gel stains. Gel stains are a little different. There is still a colorant (pigment), of course, but gel stains are an oil-based varnish, like polyurethane, for instance, along with the colorant. While both water-based and oil-based stains are liquid, gel stains have a pudding-like consistency, much thicker, that will sit on the wood surface rather than penetrate it.
Gel stains are not absorbed into the wood like water-based and oil-based versions. Since it does not sink into the wood, a gel stain tends to provide an even color and allow the wood’s character and texture to shine through. Two coats of gel stain are generally not needed.
While you are less likely to encounter a blotchy gel stain, this is not to say it never happens. A blotchy gel stain application can happen, too, just as it can with traditional stains. This is so, depending on the gel stain formula you are using, between early wood and late wood in pine. Sometimes a wood is just too porous in spots, and stains can be absorbed unevenly. This will result in the dreaded blotches.
Why Does Blotching Happen with Stain Applications?
Blotching will happen when the wood surface densities vary, and more stain is absorbed in some areas but not in others. This produces an uneven and spotty appearance that takes much away from the wood grain’s beauty. Darker colors will appear between lighter colors and create a patchy appearance, something you weren’t looking for, and it’s the darker color on the wooden surface caused by greater absorption of the stain we want to avoid.
Raw woods like oak and walnut will absorb liquid stains more evenly. However, softer woods like pine, poplar, maple, and birch will have spongy areas that will take in too much color than denser areas on the wood surface.
You can mitigate against this to an extent with proper prepping. Start with an even sanding with a fine-grit sandpaper, something like a 180-grit paper, on the wood’s face grain and 220-grit paper on end grain. When you’ve used a random orbital sander, be sure to still follow up with hand sanding using those same grit papers.
After the sanding prep, be sure to inspect the surface, wipe with mineral spirits to clean it fully, and check for any scratches or blemishes in the wood. If working with a wood that might present a more spongy surface, one that you would expect to be more absorbent for a liquid stain, apply a coat of gel stain instead.
As noted earlier, gel stains are made to sit on the surface rather than penetrate it.
You can also help equalize the raw wood density with a washcoat.
What Is A Washcoat?
A wash coat is a thinned wood finish that is applied to unfinished wood before staining. It will serve to partially seal the raw wood and will reduce the amount of stain the wood will absorb, thus reducing the chance of a blotchy appearance. It works on the more porous woods we mentioned earlier, woods like pine, alder, aspen, and birch.
If the surface of the unfinished wood has spongy areas, a wash coat will frustrate the greater absorption of the stain and help produce a more even color.
If you are ambitious, you can even make your own wash coat. Mix varnish and mineral spirits in a ratio of 2 parts varnish with 8 parts mineral spirits, and you have your very own. Use the varnish you have chosen for your project’s topcoat, too. It will penetrate into the softer spots of the wood and partially seal them to equalize the absorption of the stain and give you a more even stain application.
What Is A Pre-Stain Wood Conditioner?
Another product that is intended to frustrate stain absorption is a pre-stain wood conditioner. It is to be used before staining, as the name implies, and it will help prevent streaking and encourage a more even stained appearance. It will dry quickly and won’t hold up your project.
Minwax produces a pre-stain wood conditioner that will dry as quickly as 15 minutes after application.
- PRE-STAIN TREATMENT FOR ALL WOOD – Ensure wood projects look great with Minwax Pre-Stain Wood…
- PREVENT BLOTCHES – By Minwax Pre-Stain Wood Conditioner prior to staining with oil-based wood…
- ASSURES EVEN STAIN PENETRATION – Wood is porous, and tends to absorb stain unevenly. But this wood…
Minwax recommends using its conditioner when you are working with those previously named woods – pine, alder, aspen, birch, and maple. These woods are more porous than woods like oak, and their spongy areas will end to absorb more stain and create a blotchy application.
When You Have To Repair A Blotchy Stain Application
If your stain application does result in blotching, though, all is not lost. There are remedies, some of which you won’t like but will still give you some relief.
Let’s offer a few.
Sand it down. Yes, sand the piece down to raw wood and start all over again. Learn from the process, and choose a wash coat or a pre-stain wood conditioner as your first application. Then, move on to the stain.
Go Dark. If your project can withstand a darker stain finish, add a second coat to blend in the blotch. (How’s that for alliteration? “blend the blotch”) We’ve written about the timing on a second coat of stain, and you’ll find that article here. Use either a regular stain or a gel stain that is a darker color than the first coat. This will darken the wood evenly and blend the blotch.
Use a glaze. A glaze is a thick stain that you would apply over the film finish that’s covering the blotch you want to even out. Apply a sealer coat of your chosen top coat, and when it dries, roughen it with steel wool rubbed in the direction of the grain. This will create scratches in the sealer coat where the pigment in the glaze can catch. Clean the surface and add an even coat of the oil-based gel stain as your glaze. When it has dried fully (follow the directions on the can), you can then apply your top coat(s).
Video Demos of Gel Stain
If you’ve never used a gel stain before, here are a couple of demo videos for you. The first compares and contrasts gel stains with liquid stains; the second shows the application of gel stain on raw wood. You’ll notice in the second video there is no blotchy gel stain mark on the wood.
While you are less likely to encounter blotches when working with a gel stain, it is not impossible. There are pre-treatments available (both Minwax and Varathane produce them), and whatever color you might want from a liquid stain will be available in a gel stain option, too (again, both Minwax and Varathane are mainstreamers who offer them).
Finally, there are also remedies in the event of a blotchy appearance.
Last update on 2024-03-04 / Affiliate links / Images from Amazon Product Advertising API