Brushing Oxford Water-Based Varnishes, Lacquers & Polyurethanes By Jeff Jewitt, Homestead Finishing Products®

These brushing instructions are good, basic procedures to follow whether you are a weekend finisher, or a professional artisan. Starting with these words fresh in your mind will help you overcome many common problems in using any modern waterborne coating.
- Jeff Weiss, Target Coatings, Inc.

Water-based finishes are the most temperature sensitive of all finishes. It's best to finish at room temperature and in humidity less then 70%. The finish and wood should be at room temperature. Since water-based finishes dry quickly, dust settling in the finish is not as much of a problem as with solvent-based products, but try to finish in a clean, dust-free area if you can. Try to have fresh air flowing over the finish as it dries- finishing in a screened-in porch during warm weather is ideal.

Prepare the wood by sanding to 180 or 220 grit sandpaper. You can minimize grain raising from the initial finish coats by one of two methods:

Of the two methods- I recommend sealing with shellac when finishing over old or "questionable" surfaces that may have stripper/silicone contamination. If you are finishing over another finish like lacquers, varnish or another water-based system, sand the surface with 400 grit sandpaper then wipe with denatured alcohol. This will give a good micro-scratch for the new finish to bond onto. If you use shellac, sand with 320 after it is dry and remove all residues with a clean towel and a bit of water. When finishing over an old finish-and you see fish-eyes, or craters form, wipe the finish off, seal with shellac (2 pound cut, dewaxed) and then proceed.

Once you have base coats of the Oxford down, you can apply your topcoats. Gloss can be rubbed out to the sheen you like, (we recommend waiting 3 days minimum), by using wet/dry paper or steel wool. Satin finishes can be rubbed, but it is best to leave it alone, "off the brush". Never use steel wool if you plan to continue the finishing process with more waterborne coatings-rust spots can appear if you have not removed all of the microscopic steel dust from the finish. If in doubt use a synthetic product-3M Scotchbrite® Pads are ideal. Never use less then a gray (#7448) grade pad if you plan on applying more finish.

The final topcoats should be thinned 5-10% with cold water of with the SA5 Retarder. The best brush to use for your final coats is a soft, quality synthetic bristle brush (see the Sable-Lite Brushes). They are available in various sizes and the smallest can be used for intricate work.

When you brush, pre-condition the brush by first wetting it for a moment in water, then wring out the excess. Dip only halfway up the bristle length and then apply the finish to the surface. I like to brush it on as quickly as I can in light, smooth strokes, and then come back and "tip" if off to smooth out the finish. Unlike solvent-based varnishes, you do not have great deal of open time before it starts to dry and setup, so try to work quickly.

The worst thing you can do with a water-based finish when brushing is to fuss with it. The finish may look horrible at first, but try to walk away from it and let it flow out and settle on its own. It takes a while for the tail solvents to work; so learn to be patient before you form a final opinion on the quality of the surface. It's normal to leave a less-then-attractive mess at night, only to come back the next morning to find an acceptable finish.

Tips

Wiping Water-borne Finishes

Almost any water-borne finish can be brushed and sprayed, but few realize that it’s very easy to wipe on. Like wiping other products, it’s fast, easy and eliminates (or at least minimizes) the major problems with brushing such as bubbles and brush marks. Plus, wiping a water-borne finish eliminates the soupy, plastic look from the excess finish that builds up around the pores of open grained woods like oak. All you need is to use the right products, technique and applicators.

Materials

• Most water-borne finishes are too thick to wipe on. We find that reducing the finish approximately 20-25% by volume with tap water works best. Measure the water and stir it into the finish.
• The best applicator I’ve found is the padding cloth we recommend for shellac. It's absorbent and soft, and virtually lint-free. Simply dampen it with about 1 ounce water, then wad it up so it fits into your hand. Squeeze it to remove any excess water. It should not be dripping wet. You can double up single padding cloths to make a larger one if necessary.
• Our flip-top bottles make excellent dispensers for the finish.
• We recommend wearing thin gloves when doing this finish both to protect you from the solvents in the water-borne, as well as keeping you fingers from getting very sticky.

Technique

To minimize grain raising and to add some depth and/or color, wipe on a dewaxed shellac. A 2 lb. cut works fine and when dry, sand with 600 grit sandpaper (216u works best). Applying shellac is also a good way to avoid contamination problems if you’re wiping finish over a stripped finish, or an unknown finish. Remove all the dust after sanding with a damp cloth. If you know what the finish is and do not want to use shellac, sand the old finish with 400 grit, then 600 grit and remove the dust with a damp cloth.

To pad the finish, dispense about a half to an ounce of finish on the bottom of the pad. Coming in from and edge, wipe the finish in a full swath to the other edge. Don’t press down too hard at the beginning or you’ll dispense too much finish and lift up slightly as you get to the other edge. Work the surface in overlapping strokes of an inch from the top to the bottom. If you miss a spot or get some excess finish in an area, fix it immediately. However, once the finish has started to tack, wiping it usually makes things worse.

The finish takes around 10-15 minutes to set up enough to wipe it again. It helps to have good air movement. If you’re in a hurry and want to speed things up, use a hair dryer and wave hot air over the finish to help it set. This technique is particularly useful for on-site finishing or repair work.

Apply another coat of finish, working it in the same way. When doing molded edges, you can simply conform the pad to the shape of the molding and wipe. For right angles, push the pad applicator into the corner, and drag it out towards the middle. For turnings, wrap the applicator around and work the pad around.

Color Changes

As you work, you can make color changes or add depth easily by adding either pigments or dyes to the finish. We recommend using Vivitone™ Waterbase Concentrated Pigments or TransTint® Dyes. Simply add the amount of color into a small amount of the finish (I use the large plastic beakers) and then dispense the colored finish into the pad. Wipe the surface in the same way you apply the finish, using very even strokes. Try to avoid too much of an overlap. When you’re done, you can easily rinse the color out of the pad and keep using it for clears. Always seal in the last color coat with at least two clear coat applications to protect it.

Written By Jeff Jewitt. Reprinted with permission by Jeff Jewitt.
All Rights Reserved. Copy Right June 2000. Not to be reprinted without explicit permission by the author.