When to Use a Penetrating Wood Finish Instead of a Film-Forming Finish

Most of the finishes you’ll see used on wood products are film-forming. And there are several reasons for this:

They meet and, in most cases, exceed the KCMA standard (how a finish performs against typical household substances and extreme temperatures)…

They are highly durable…

And they are quick and easy to apply using standard finishing equipment and techniques.

Just to ensure we’re all on the same page, by definition, a film-forming finish creates a coating or “film” on top of the wood surface. And they’re ideal for the vast majority of projects.

But there are some situations when another finish type is required. And that’s where penetrating finishes come into play.

In this article I’ll outline when and why a penetrating finish is called for. And I hope that by the end of this article I’ll have convinced you that this unique family of finishes deserves to be added to your finishing lexicon.

Penetrating Finishes Can Take a Beating. Literally.

Surfaces that will be subjected to extreme abuse – such as those designed to be hammered upon – need a finish that can tolerate dents and dings.

For example, to the work surface of my workbench, I applied 100% pure hemp oil, a product known for its ability to penetrate deeply into the wood. Three coats were applied, and after having curing for a few weeks, two coats of furniture paste wax were rubbed on to enhance the protection.

But when it came to the drawers, I elected to seal the insides with Target Coatings EM1000 sanding-sealer, then applied Target Coatings EM2000 water-based alkyd varnish to the fronts because a film-forming finish makes better sense for those parts of the workbench that won’t be subjected to such extreme abuse.

Penetrating Finishes Tolerate Cutting, Chopping and Extreme Heat

Example 1: Kitchen Tables and Islands
Kitchen tables and islands need to handle all sorts of abuse: they’re pressed into service as chopping boards, trivets to hold oven-hot baking or frying pans and to handle the day-in, day-out work that goes on in a kitchen.

For this reason, I apply mineral oil, which is also a food-safe product, to the tops of kitchen islands. And when the time comes when the client feels the need, a simple sanding and finish reapplication will renew the surface.

I’d like to point out that though clients often specifically request I paint the legs and apron with milk paint, a more durable product such as Target Coatings EM6500 pigmented lacquer can be a consideration.

Example 2: Charcuterie (or Cutting) Boards
By their very name, cutting board surfaces will be subjected to knife cuts. For this reason, I again use mineral oil, a food-safe product. And whenever the surfaces need to be renewed, it’s a simple matter to sand the knife cuts out and apply a few fresh coats.

Note: If I were making a butcher’s chopping block with an incorporated table base, I’d most likely finish the base in a more appropriate finish such as Target Coatings EM8000 conversion varnish, with cross-linker CL1000 added to improve the durability.

When Beauty, but Only Limited Protection is Called For

Let’s face facts: sometimes a quick and easy finish – such as one coat of tung oil – can be the ticket.

A good example of this is the jewelry box I made for my 10-year-old granddaughter. And even if it is dropped, any dents won’t result in the finish cracking. Fast, easy, effective. A penetrating finish is the perfect match for such items.

Easy on the Hands, While Improving Control
When it comes to paddles or oars, many serious watercraft users prefer the feel of bare wood, which they state provides for greater control.

So, to add protection without fully forfeiting that desired trait, I would typically apply a penetrating finish of 100% pure hemp oil to the parts they touch and a more protective, film-forming finish such as Target Coatings EM9300 polycarbonate urethane elsewhere. This is another great example where mixing finish families allows me to achieve even greater results.

In Summary…

I think the old saying, “There’s a time and place for everything”, really summarizes the best approach to selecting finishes.

Penetrating finishes for those projects or parts of a project where usage so dictates, and film-forming finishes for everything else. That’s the way I see it.

Please let me know what you think or read what others are saying in the comments section below — I’d love to hear from you! And if you have another topic you’d like to have me cover, feel free to let me know. I’m here for you.