Canadian Woodworking

Aqua Coat clear grain filler


A superior water based grain filler that dries super clear.

Author: Carl Duguay

If you want to achieve a ‘smooth as glass’ finish on open grained woods, then you really need to use a grain (aka pore) filler. Woods such as oak, ash, elm, mahogany, chestnut, walnut, wenge, and teak are characterized as having ‘open grain’ because the wood pores are large. In contrast, ‘closed grain’ woods like hard maple, cherry, poplar, beech, and bubinga, have much smaller pores. A grain filler levels out the surface of open grained woods by filling the pores, reducing the number of topcoats (and the requisite sanding between each coat) that you need to apply to achieve that smooth finish.

COMPANY: Aqua Coat
PRICE: $17.95 US (pint); $29.95 (quart)
SOURCE: Leevalley.com

Of course, you don’t have to fill the pores of any wood before applying a finish – and a lot of woodworkers don’t. It’s a matter of what you want the final surface to look (and feel) like. Grain filling simply enables you to achieve that super smooth finish fairly quickly. The best candidates for grain filling are large horizontal surfaces – the tops of tables, desks, sideboards, dressers, fancy boxes, and the like.

I recently tried Aqua Coat’s Clear Grain Filler. What I really like about this product is that it’s super easy to apply and clean up, sands easily, dries quickly so that I can get on with the finishing job, and doesn’t impart any colour to the wood. It’s also virtually odourless, which is a real boon when working in a small, windowless shop.

Aqua Coat Clear Grain Filler comes in pint (shown), quart, gallon, and 5-gallon formats. If you don’t use a lot of open-grained woods, or you just want to give it a try, then the pint format is probably the one to choose. The type of wood you’re filling, how many coats you apply, and how careful you are in scraping the excess back into the container will affect the coverage you can expect to get.

Before applying the filler I apply a sealer – essentially a first thinned application of your topcoat. Alternatively you can apply a 1 pound cut of shellac. The sealer raises the grain (swell the wood fibres), so you’ll want to sand off these fibres. Once you’ve sanded back the raised grain, it won’t occur again.

The Aqua Coat Filler has the consistency of a slushie (or perhaps thick pancake batter) – thick enough to scoop up some with a spatula or credit card, and drop onto your work surface.

Because the Aqua Coat Filler is water based it dries more quickly than a solvent based filler, which means you’ll want to work in small sections at a time, and reasonably fast. You don’t need to mix Aqua Coat Clear Filler before using it. Just scoop a tablespoon or so and drop it on the work surface. The objective is to pack the filler into the pores of the wood. You can do this with a rubber squeegee, an old credit card, or even a piece of coarse fabric. I prefer a squeegee because it doesn’t waste filler. I work the filler diagonally to the grain. Aqua Coat spreads easily, and I find that I can do about one square foot of surface in under a minute. Though you can, I haven’t found it necessary to thin the Aqua Coat with water.

Using a squeegee makes it easier to control the filler, and usually I end up with a very thin, even coat spread over the work area. You can easily see if all the pores are filled by looking at the surface at an angle, against a bright light beamed obliquely to the surface. Once the surface begins to dull I wipe it down with a cloth, across the grain, just enough to remove any bits of paste that haven’t gone into the pores. I’m not overly concerned about getting every single micrometer of space filled, as I always lay on a second coat of filler after the first coat has dried for at least an hour. Before repeating the process I’ll lightly sand the surface with 320- or 400-grit paper.
On the ash sample shown in the photo above two thin coats of filler were sufficient to give a perfectly smooth surface that didn’t impart any noticeable colour to the wood. You can apply either a water based or solvent topcoat over the Aqua Coat.

If you do any amount of fill, then I highly recommend that you give Aqua Coat a try. I think you’ll be pleasantly surprised at how well the product performs. And, as the saying goes, nothing ventured, nothing gained.

Key Features:

  • Non-Shrinking
  • Quick Drying
  • Easy Sanding
  • Tintable
  • Minimal Shrinkage
  • Water Clean-up
  • Non-Flammable
  • Non-Combustible
  • Low Odor

Last modified: September 29, 2023

Carl Duguay - [email protected]

Carl is a Victoria-based furniture maker and the web editor at Canadian Woodworking & Home Improvement.


  1. Advertisement

    1. Currently there are no Canadian dealers. However you can order direct from Aquacoat (which I have done) or you can purchase it on Amazon.ca (search Aquacoat).

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