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The Ultimate Guide to Wood Conditioner

Once upon a time, I believed wood conditioner was a gimmick from Minwax to make more money. Then I stained a piece of pine, and it was absolutely hideous (see below.) Suddenly, I was sold on wood conditioner, and wondered exactly what it was and how it worked.

Have you ever wondered what exactly is wood conditioner, and how does it work? I set out to answer every question you've every had about wood conditioner, so come find out!

Wood conditioner is an ultra-thin layer of finish that reduces stain penetration in softwoods. This results in a more uniform and desirable result when staining wood. Not all wood requires wood conditioner, but most softwoods benefit from it.

There are a number of nuances to wood conditioner, so keep reading so you know exactly how and when to use it!

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How to Use Wood Conditioner

The instructions on the Minwax say to liberally apply the wood conditioner, let it sit for 5-15 minutes, then wipe off any remaining product. They recommend applying the stain within two hours.

However, wood finishing expert Bob Flexner believes these instructions are incorrect. The theory is that because this is an ultra-thin finish, you should let the finish dry completely, then apply the stain. Otherwise, he says, the wood conditioner is simply diluting the stain. While this does reduce penetration, he feels a better result is achieved by letting the wood conditioner try.

I tested this out on cheap 1×4 wood I picked up at Home Depot. Frankly, the results were inconclusive:

Have you ever wondered what exactly is wood conditioner, and how does it work? I set out to answer every question you've every had about wood conditioner, so come find out!
Have you ever wondered what exactly is wood conditioner, and how does it work? I set out to answer every question you've every had about wood conditioner, so come find out!

The wood I chose absorbed stain pretty evenly from the beginning, so there wasn’t a significant change from using the wood conditioner. You can tell that wood conditioner that was given 5 minutes to dry results in a lighter stain – which makes sense, since the liquid wood conditioner is still present in the wood, diluting the stain.

If you’re wondering what the “rag” test was, in that application there was no wood conditioner, but I applied the stain with a rag rather than a foam brush. All the other applications were applied with foam brush.

Sometimes I have better results staining with a rag rather than a foam brush, since that also reduces stain penetration, and I wanted to put that to the test here.

So, what will I do in the future? I plan to test my stains and wood conditioner on scrap wood before applying it to my piece. That way, I can see A) if wood conditioner is actually necessary, B) if a 5 minute application vs 24 hour application is better, and C) if the stain is actually the shade I’m looking for once it’s applied to the wood.

Is Wood Conditioner Actually Necessary?

To determine whether wood conditioner is necessary for your piece, test your stain on a piece of scrap wood. Does it absorb evenly, or is it blotchy and unattractive? If the stain is blotchy, it’s worth using wood conditioner; if it applies cleanly, you probably don’t need it.

If you didn’t build the piece from scratch, or if you’re staining wood attached to your house (flooring, molding, etc,) test your stain in an inconspicuous spot. For furniture flips, I test on the bottom side of the tabletop or on the back of leg.

If you’re forced to test on a spot that can be seen, remember that if you don’t like the look, you can always sand down that spot to remove the stain.

In instances when I have plenty of space to test (aka, I have scrap wood from the project,) I tend to test all of my different options to see which one I like the best. I test wood conditioner vs no wood conditioner, every stain I’m considering, different finishes with those stains, etc.

Sometimes, I even test different application methods, like applying with a rag vs applying with a foam brush. This helps ensure that when I finally apply my finish to the piece, it looks exactly how I want it to to look.

When You Shouldn’t Use Wood Conditioner

Wood conditioner is intended to be applied before staining. It is absolutely unnecessary after applying the stain, unless you’re intending to apply another stain.

It is also extraneous before applying finish. In fact, for some finishes it may prevent the finish from adhering or drying properly, so if you’ve applied wood conditioner, you should wait at least 24 hours for it to fully dry before applying finish.

You should not apply wood conditioner before painting a piece. Paint lies on top of the wood and does not soak into the wood, so there is no purpose to applying wood conditioner. Instead, consider applying primer, which hides knots and tannins in the wood, and helps the paint adhere to the piece.

Finally, be sure you’re applying the correct wood conditioner to the piece. Your wood conditioner should match the type of stain you’re applying. If you’re applying water-based stain, you should use a water-based wood conditioner. If you’re using an oil-based stain, you should use an oil-based wood conditioner.

If at any point you need to mix oil or water based products, apply Zinsser’s Shellac Sealcoat between them. This will keep the products separated, and allow the top product to still adhere to the piece.

Does Wood Conditioner Go Bad?

Wood conditioner can go bad if exposed to extreme temperatures, humidity, or airflow. This will be obvious, however, as when wood conditioner goes bad it separates into a liquid portion and solid portion. If your wood conditioner is still a single liquid, it is in good and usable condition.

This knowledge comes from experience. After failing to tightly replace the lid on my wood conditioner, I didn’t use it for a period of 3-4 months. When I reopened it for my next project, it was a two-part mess. Luckily, I had another can ready to go, so I tossed the remains and opened a fresh can.

Alternatives to Wood Conditioner

If you’ve determined that you need to use wood conditioner and you don’t have any in the house, you’ve got a couple options. Since wood conditioner is just thinned finish, thinning most finishes will result in a quality wood conditioner. Here are a few recipes you can try.

  1. Polyurethane + Mineral Spirits – Mix one part oil-based polyurethane with two parts mineral spirits. This mix is probably the closest one to the commercial wood conditioners available for sale.
  2. Shellac + Denatured Alcohol – Mix one part shellac (I recommend Zinsser’s Sealcoat because it is premixed, widely available, and wax-free) with one part denatured alcohol.
  3. Lacquer + Lacquer Thinner – Mix three parts lacquer thinner to one part lacquer.

For all three of these recipes, let them fully dry before applying stain. The length of time varies based on the product you used – check the can of your polyurethane/shellac/lacquer for an estimate. Your DIY wood conditioner should not take longer to dry than the time length for the undiluted base.

If you don’t have any of these products on hand, there are a few other things you can do to reduce stain absorption in wood, which is the purpose of wood conditioner.

First off, try applying your stain with a rag instead of with a foam brush on a piece of scrap wood to see if it makes a difference. I’ve found that allows me to control the amount of stain that reaches the wood, meaning less stain penetrates the wood because I’ve applied less to the piece.

Gel stain is another option. Gel stain is simply thickened oil-based stain. Because it is thicker, less stain is absorbed into the wood. There are a couple of different applications for gel stain, but staining soft and porous woods is one of the primary ones.

If you’ve been relying on wood conditioner to stain softwoods, I challenge you give gel stain a try. It’s easy to use, and means you can skip a finishing step (the wood conditioner,) which is always a win in my book!

What’s the Difference Between a Washcoat and Wood Conditioner?

“Wood Conditioner” and “Washcoat” are basically different names for the same thing. Wood conditioner typically refers to a pre-mixed version sold in stores, while washcoat is more often referring to DIY mixtures woodworkers make at home. They perform the same function.

Regardless of the name, the purpose of both washcoats and wood conditioner is to reduce absorption of stain on soft and porous woods, resulting in an even and non-blotchy result.

The recipes listed in the previous section would all be traditionally referred to as washcoats.

What Happens If I Leave Wood Conditioner On Too Long?

If you’ve left wood conditioner on your wood, there are two possibilities:

  1. You wiped off the wood conditioner after application, but haven’t applied the stain for more than 24 hours. In this case, you’re fine. The wood conditioner has dried, and you may want to apply more wood conditioner depending on your finishing plan, but the dried wood conditioner won’t harm the wood or your project.
  2. You forgot to wipe off the excess wood conditioner after application, and now it’s dried on top of the wood. Since wood conditioner is just very thin varnish, a thin layer has dried on top of the wood. Grab a sander, and briefly sand with a medium/high grit sandpaper. This should remove the wood conditioner.

Either way, leaving wood conditioner on too long is no reason to panic. A quick sanding will remove any dried wood conditioner from the piece, leaving you ready to continue finishing.

Other Wood Conditioner FAQs

Is wood conditioner a sealer?

Wood conditioner is a very thin sealer. However you would need many layers of wood conditioner to actually seal the wood. If you’re interested in sealing the wood before finishing or staining, you’re better off using Zinsser’s Shellac Sealcoat.

Does wood conditioner lighten stain?

When applied as directed, most wood conditioners lighten stain. This is because manufacturers recommend applying stain within two hours of application, which means the wood conditioner hasn’t fully dried and is still present in liquid form. This dilutes the stain, lightening it.

Can you polyurethane over wood conditioner?

If you are using an oil-based polyurethane, you should have no problems applying polyurethane on top of wood conditioner, given the wood conditioner has fully dried. If you’re applying a water-based topcoat, apply Zinsser’s Shellac Sealcoat to seal the wood first.

Does wood conditioner make stain darker?

Wood conditioner does not make stain darker. If anything, it makes stain lighter, because it dilutes the stain during application.

Do you need to sand after applying wood conditioner?

Whether or not you need to sand after applying wood conditioner depends on what kind of wood conditioner you applied. Oil-based wood conditioner does not need to be sanded. Water-based wood conditioner, on the other hand, raises the wood grain and requires sanding after application.

Is wood conditioner necessary for oak?

Oak takes stain well, and therefore wood conditioner is not usually necessary. However, if you have a piece of scrap wood, it is worth testing your stain on the scrap first to ensure that wood conditioner is not required.

Can you paint over wood conditioner?

Given that the wood conditioner has fully dried, it can be painted over without problems. If you’re concerned about adhesion, I recommend applying a layer of primer first to make sure the paint adheres.

Are mineral spirits a wood conditioner?

Mineral spirits are not intended to be a wood conditioner. However, if mineral spirits are applied to wood directly before stain, it will dilute the stain, lightening the stain and reducing penetration in the same way many wood conditioners do.

However, once dry, mineral spirits will have no impact on stain penetration, while many dried wood conditioners can still be effective.

I didn’t use wood conditioner. How do I fix blotchy stain?

If you didn’t use wood conditioner the first time, sand down your piece back to the original shade of wood. Then you can use wood conditioner before applying the stain, which will fix the blotchiness.

Alternatively, you can try gel stain or applying finish with a rag, both which should help reduce stain absorption similarly to wood conditioner.

There are a couple of other options too, which I cover in my post about what to do when you don’t like your wood stain color!

Can I use water instead of wood conditioner?

Water cannot be used as wood conditioner. In fact, when using a oil-based stain, this will cause difficulties in stain application.

Is wood conditioner the same as primer?

Wood conditioner is not the same thing as primer. Wood conditioner is a thin product that soaks into wood to reduce wood stain penetration, while primer is a thick product that sits on top of wood as a base for painting.

Do I need to use wood conditioner before using gel stain?

Gel stain is thick enough that it doesn’t need wood conditioner before application. The thickness alone prevents blotchy stain penetration, so wood conditioner is unnecessary.

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