“To Fill or Not to Fill… That is the Question.” This article walks you through how to work with grain filler.
When I was making furniture for a living, nearly every one of my clients had their own idea of what constituted “finely finished” furniture. That enabled (or should I say “forced”) me to develop a wide lexicon of finishes to meet their diverse tastes. Today I’d like to address one particularly important aspect of finishing, and that’s how to deal with open grained (AKA open pored) woods like oak, mahogany, walnut and butternut.
There are two principal choices finishers have for working with such surfaces: leave the grain pores open or fill them.
Although there is simply no right nor wrong answer to this question – as it all comes down to client choice – one fact remains: if you need the open grained wood to have a perfectly smooth surface, you have no choice other than to fill the pores. And although some fill the pores by spraying several extra coats of finish and sand between each and every one of them, there’s a much more efficient way: use a grain filler.
Although there are several different grain fillers on the market, ensure you choose one that is fully compatible with the other finishing products (sealer, colorants, topcoats, etc.) you’ll be using on the piece.
I prefer all my finishing products to come from the same manufacturer so this will never be a problem for me. But if yours come from different manufacturers, run a few test panels just to be sure.
I have found Target Coatings HSF5000 series of grain fillers gives me consistent, exceptional results. And because they’re water-based, they dry quickly.
For those clients who prefer to see the wood grain, I use HSF5100, which imparts a neutral, translucent color to my work. The two other fillers in the Target Coatings line are for surfaces that will be painted or receive tinted lacquer: White base HSF5200 for light colors and Grey base HSF5300 for darker colors. And to save time and money you can tint these products so they’ll also act as primer.
HOW TO FILL PIECES THAT WILL BE CLEAR FINISHED
Fillers are used on all open grained woods regardless of what type of finish is desired: stain, paint, tinted lacquer, or clear (also known as “bright”). Clear finished pieces are the simplest to describe, so let’s start with them. But rest assured, this article will also touch upon how to fill pieces using those other finishes.
Seal the Wood: Before applying pore filler, lightly seal the entire surface. This will help keep the rest of the surface from taking on any of the filler’s color. I prefer Target Coatings EM1000 Sanding Sealer reduced 50% with water* for this job. It also does a great job of sealing the wood to get it ready to accept whatever other products I’ll be applying, but by adding dyes or UTC (Universal Tinting Colorants), it can also do double-duty as a toning medium. How’s that for flexibility?!
Ensure you thoroughly sand the surface down to P220 grit sandpaper before applying the sanding sealer. After the first coat, sand the surface again with the same grit sandpaper. This will get rid of those “whiskers” that show themselves as the grain is raised. Follow this up with a second coat of sanding filler, but don’t sand this last sanding sealer coat.
Special Effects: Whereas many like the neutral/translucent color that the HSF5100 Neutral Filler base imparts to open grained woods, some prefer them to color contrast. This can be achieved simply by tinting the filler with water-soluble dyes and/or pigments. Conversely, others want those open grain areas to take on the same color as the rest of the wood. Again, the objective here is to meet your or your client’s desires, be they neutral, contrasting, or alike. Target Coatings HSF5000 series fillers allow you to achieve this.
Applying Filler: All Target Coatings HSF5000 fillers can be either sprayed, brush or roll applied, but I prefer to spray it on. Although it’s a relatively high viscosity product, I’ve found that when spraying HSF5100 (the neutral filler base version), which is what I use on clear finished pieces, a 1.3mm needle/nozzle/air cap set on my Fuji Spray T75G HVLP turbine powered spray gun works quite well. But if you’re wanting to spray the higher viscosity white or grey base primer versions, you’d best use a 1.8mm set. For those who prefer to use compressed-air HVLP spray guns such as Fuji Spray’s LX-20, move up to the next higher needle/nozzle/air cap set (e.g. 1.4mm for HSF5100). Regardless of the set you mount, apply a 2 – 3 mil wet film thickness per coat. Two coats are fine for all but the most heavily pored woods, as they usually require an additional one or two more coats.
Drying Time and Sanding: Allow at least 2 hours drying time between grain filler coats to ensure it has dried enough to sand properly. Sand after each coat with P320 grit sandpaper but don’t press too hard or you’ll run the risk of removing too much of the filler from the open pores.
Lock in your Filler: Once I’ve achieved the smooth surface look I’m aiming for, I lock it in with another coat of Target Coatings EM1000 Sanding Sealer, again – reduced 1:1 with water (50% reduction*) before proceeding with whatever topcoat product I’ve chosen. Again, I choose Target Coatings sanding sealer because I know it will be compatible with their HSF5000 series grain filler.
FILLING PIECES THAT WILL BE STAINED, PAINTED OR HAVE TINTED LACQUERED APPLIED
I mentioned at the beginning of this blog that I would also address pore filling pieces that will be either stained or have paint or tinted lacquer applied, so before moving on to top coating, let’s cover them now.
Stained Work: Start by staining your piece in the manner you usually follow for closed-grained woods. Once the stain has properly dried, ask yourself whether you want the open grain pores to be the same or a contrasting color to that which the stain imparted. Again, remember that if left un-tinted, the HSF5100 neutral filler base will impart virtually no color to the pores. If you want any other color, follow the advice I gave in the “Special Effects” paragraph above, and follow that up with the afore-mentioned EM1000 sanding sealer to lock everything in and prepare it for top coating. But be careful not to sand all the way through the sanding sealer to the stained surface; hand sanding rather than using sanding machines is the safest way to go.
Painted or Tinted Lacquer Work: Once you’ve applied the sanding sealer coats as described above, choose your grain filler. With Target Coatings, that will be either HSF5200 for colors in the lighter end of the spectrum or HSF5300 for the darker colors. Tint the grain filler with the appropriate water-friendly tinting product of your choice. Go ahead and apply the tinted filler in the same manner described above for clear finishes. Once the necessary coats of paint or tinted lacquer have been applied, depending on those products, you may or may not have to move on to applying a topcoat. If top coating is desired, proceed with top coating.
Now that you’ve gone to all that effort to fill your open grained furniture or cabinet piece, it’s now ready to be top coated with the product of your (or your client’s) choice. Rest assured that Target Coatings has a complete range of quality products to meet those needs. Check them out at: https://www.targetcoatings.com/shop/
I hope that I’ve given you some great ideas on how to deal with open grained woods. Please let me know what you think as I’d love to hear from you regarding this topic, or any other finishing challenge.
*Note from the Editor: It is recommended on the Target Coatings website that the EM1000 Universal Sanding is NOT used under the HSF5000 Primer/Surfacer or the EM6500 Pigmented Lacquer Series. However, we have learned that by reducing the EM1000 with water 50% (1:1) and by applying the reduced EM1000 in coats not exceeding 2mils wet, followed by a thorough sanding with P320 sandpaper, a quality preseal can be obtained to create the grain-filling properties that are described in this blog post. We strongly recommend that you make a test/storyboard on the wood species being used to confirm your process before proceeding to the final finishing schedule.
Marty Schlosser has nearly 50 years experience as a furniture designer, maker, and finisher, including a career in production-level spray finishing. Often called, “the industry’s go to expert,” Marty is a past-president of the Ottawa Woodworkers Association (and a proud recipient of their Danny Proulx Memorial Award), and the founding member of Kingston Wood Artisans, a local woodworking club in Kingston, Ontario, Canada where he and his wife reside.