Sanding Sealer vs. Wood Conditioner: When to Use Each

By MWB-Team •  Updated: 06/04/23 • 

Getting a near-perfect wood finish involves a lot, and there’s also a lot that can go wrong. Sanding sealers and wood conditioners are used when finishing wood to help you get better wood-finishing results. However, these two are very different, each used for a different problem.

What is a Sanding Sealer?

A sanding sealer is simply a thinned version of a lacquer-based or varnish-based finish modified with zinc stearate. The zinc stearate additive makes sanding the finish easier and smoother so that the other layers go on smoothly. The zinc stearate makes the finish easier to sand by making it powder instead of gummy.

Minwax Lacquer Sanding Sealer

This Minwax sanding sealer is lacquer-based and seals a wood's surface, providing an easy-to-sand coat after one hour. It is available in both brushing or aerosol forms for easier application.

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When to use a Sanding Sealer

Sanding the first coat of a finish smooth makes all other additional coats go on smoothly and produce better results. However, some finishes, such as varnish and lacquer, are very difficult to sand. If you’re using lacquer or varnish as a topcoat, start with a sanding sealer, which makes it easier to sand, and, therefore, subsequent coats can go on smoothly.

Sanding sealers are usually only provided for lacquer and varnish finishes. A sanding sealer is not needed for polyurethane, shellac, and other water-based finishes because these finishes are relatively easy to sand.

Although sanding sealers make it easier to sand the first coat, zinc stearate will also weaken the bond of the finish to the wood. When using a sanding sealer, it is best not to apply more than one coat. If you can do without a sanding sealer, all the better. However, if you’re working on a large job, a sanding sealer is good and worth trading off some durability for much easier sanding.Check our guide on sanding sealers for a more informative read.

What is a Wood Conditioner?

A wood stain conditioner, also called a pre-stain conditioner, is a thinned finish that reduces stain penetration in some problematic woods. Most brands of wood conditioners are one-part polyurethane or alkyd varnish thinned with two-part mineral spirits. Wood conditioners are usually used for oil-based stains. There is no need for wood conditioners for water-based stains because they don’t cause blotching as oil-based stains.

A wood conditioner reduces stain penetration for problematic woods like pine, alder, fir, and aspen that are harder to stain. This results in a uniform and desirable stain finish.

Minwax Clear Pre-Stain Wood Conditioner
$18.48 ($0.58 / Fl Oz)

The Minwax pre-stain conditioner treats wood surfaces after sanding before staining to prevent blotches and streaks. It's easy to apply and wipe off the excess. It evens out a wood's surface, so the stain blends in well.

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When to Use a Wood Conditioner

To reduce or eliminate blotching, a wood conditioner is used after sanding and before applying a stain to the wood. Blotching is the uneven stain coloration caused by the difference in wood densities. Pine, one of the most popular woods used by woodworkers, blotches worst.

Once you apply a wood conditioner, wipe off the excess after 5 or 10 minutes and leave it to dry overnight. Once dry, apply your stain normally and wipe off the excess before it dries.

However, using a wood conditioner might cause the stain color to be lighter because the stain is prevented from going deeper into the wood fibers. To make it darker, leave some excess stain on the surface or apply a second coat after the first dries up.


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