Finishing

Finishing is the step that can make or break the final results of a project. A project can take a long time to complete, painstakingly ensuring all joinery is cleanly cut, square, and solid. However, you can very quickly ruin the results with a poor application or choice of finish. Once applied, it is difficult and labour-intensive to remove most finishes.

I've tried several different finishes and application techniques with varying results. Below are details of finishes and techniques I've used successfully and when I chose one option over another. For my projects, I prefer using clear finishes to bring out the natural colour of the wood. For the occasional project that uses a stain, I haven't encountered many difficulties applying a stain. However, be conscious of the wood's ability to accept specific stain types and follow the vendor's instructions.

Preparation

An excellent finish begins with proper surface preparation. Long before applying the first coat of finish, there is a lot of work that has to take place to ensure the best results. Any flaw in the construction process or in the wood preparation is amplified when applying the finish, such as tool marks, glue overflow, or even scratch marks from not using a fine enough sandpaper grit.

Recommended Preparation Steps

1. Smooth plane visible surfaces before assembly, which significantly reduces or eliminates the need to sand. The surface left by a finely tuned smooth plane is pristine and ready for finish or, at worst, requires only a light sanding with the finest grit sandpaper.

2. Guard against or thoroughly clean up glue squeeze-out. Most woodworking glues seal the wood, preventing stains and finishes from penetrating and leaving visible discolouration and blemishes in the finish that mar the appearance of the piece. Avoiding the finishing issue due to glue squeeze-out is a crucial step to ensuring a high-quality finish. Once the glue has dried on the wood, it is challenging and time-consuming to properly remove without damaging the wood surface below.

   a. Cut tenons just short (1/6" to 1/8") of the mortise depth to leave room for extra glue and prevent squeeze-out. Also, chamfer the edges of a tenon.

   b. Cover the edges of a joint with painter's tape to prevent the glue squeeze-out from going on the wood and leaving only a very fine glue line after removing the tape. Just like painting, it is essential to remove the tape while the glue is still wet.

   c. Glue up panels at a thickness greater than the finished thickness. The additional thickness allows for the final planing of the surface either by hand or by machine to remove unsightly glue lines. A card scraper or chisel plane is useful for cleaning panel glue lines before planing.

   d. Let the glue set for about 30 minutes and then carefully remove the glue with a sharp-edged tool. An old half-inch chisel works great and allows me to get into corners. If timed correctly, the glue will pull off reasonably cleanly from the wood joint.

   e. Avoid using water to wipe away freshly squeezed-out glue, unless using hide glue where warm water dissolves the glue sufficiently to avoid leaving a glue stain.

f. It's almost impossible to avoid all glue squeeze-outs even deploying the preventive measures above, so if you miss a spot and the glue has already set too far, leave it to harden fully. Once fully set, use a very sharp chisel to remove the glue, being very careful not to dig into the wood below. The glue usually cracks off the surface, leaving it reasonably clean, and removing the remaining glue altogether requires a little sanding.

1. Sand with increasingly finer grits of sandpaper. With my usual surface preparation, I can typically start sanding with 220 grit, then follow with 320 using a cork sanding block. In cases on final surfaces prepared with a smooth plane, it only requires a light sanding with 320 grit sandpaper or a sanding pad. In rare cases and only for isolated spots, usually difficult grain, I'll start at 180 grit followed with a card scraper to create a finish-ready surface.

2. Be aware that certain types of wood only work with specific or limited stain types or finishes. Also, some woods may require a pore filler or sealer before finishing. Do your research when working with new wood species. I've only used a sealer once and wasn't satisfied with the results. In most cases, a coat of shellac works as a sealer if needed but some open pored woods benefit from using a filler.

   a. Maple requires an aniline dye to colour.

   b. Cherry can be challenging to avoid blotching.

Preferred Clear Coat Finishes

I work mostly with three types of finishes depending on the project and its intended use. My first choice is a rub-on, oil-based varnish which is all-natural, looks great, and is the easiest to apply. Next would be shellac, which again is all-natural but can be challenging to apply with flawless results. For projects that require greater protection from moisture or heavy use, I use a water-based polyurethane finish.

There are countless types of finishes and techniques for finishing wood but as I prefer the natural beauty of the wood, I limit myself to the three finishes mentioned above. With these finishes, adding artist pigments to enhance the wood's colour allows for applying the stain and finish all in one go. It also allows you to adjust the tint or colouring with subsequent layers and possibly make adjustments to achieve the intended finish results. Milk paint is a finish I intend to try, which is another all-natural finish that will have to wait for the right project.

Varnish Oil

My introduction to varnish oil came when I took a one-day sharpening class at the Unplugged Workshop in Toronto on March 21st, 2017, conducted by Tom Fidgen. After learning to sharpen a plane blade, we prepared and dimensioned boards to create a bench hook that we finished with varnish oil. I purchased a can of Tried and True varnish oil that day and have been using it with excellent results ever since. Buffing results in an extremely smooth-to-the-touch, lustrous finish.

Application:

• Apply a thin coat with a lint-free cloth.

• Let it sit for at least an hour to allow the oil to penetrate the wood.

• Rub with a lint-free cloth until the surface is completely dry.

• Allow 24 hours to cure, occasionally checking for spots that require additional rubbing to remove excess.

• Burnish with a soft cloth and add a second coat repeating the steps above.

Alternative Homemade Recipe 1:

• 50% Tried and True Varnish Oil

• 50% Epifanes rubbed effect varnish

Alternative Homemade Recipe 2:

• 3 parts mineral spirits

• 2 parts polyurethane

• 1 part boiled high-quality linseed oil

Alternative Homemade Recipe 3:

• 1 ½ cups mineral spirits

• 1 cup brushing varnish

• ¼ cup boiled linseed oil

Shellac

Shellac is a resin secreted by the female lac bug, on the trees in the forests of India and Thailand. It is processed and sold as dry flakes that are dissolved in alcohol to make liquid shellac. I ran a Google search for shellac and the top links provided were all related to fingernail polish, which signifies that it has fallen out of favour as a wood finish. Given shellac's non-toxic nature, it has been used as a coating for candy and pharmaceuticals for years and dates back as a wood finish for over 3000 years.

As a wood finish, dry shellac flakes are available in several different grades that delineate the level of refinement. Dewaxed shellac is best as a wood finish, as wax-laced shellac can cause adhesion problems. Dewaxed shellac works as an excellent sealer over stains to prevent bleeding and is compatible under varnish and polyurethane. You can also use shellac over an oil finish, such as linseed oil, that produces an immediate antique appearance on new wood.

While the varnish oil finish discussed first is the easiest to apply, shellac provides the best-looking finish that brings out the natural colour and figure of the wood while providing better protection. For me, the great depth and sheen flexibility, from satin to high gloss depending on the application shellac produces, has no equal among modern finishes.

Shellac's consistency is determined by "cut." I usually mix a 2 lb. cut to start. A 2 lb. cut is 2 lbs. of shellac flakes per U.S. gallon of denatured alcohol solvent. Shellac is usually not mixed by the gallon for my use, especially since shellac has a limited shelf life. A 2 lb. cut is a 1:4 ratio, so add 1 oz. of shellac flakes to 4 fl. oz. of denatured alcohol, occasionally shaking until all of the flakes have dissolved, usually overnight is sufficient.

Shellac is best used fresh, so I only mix quantities I'll use and never use it if more than a couple of months old. If shellac is too old, it won't cure and remains soft and tacky. Also, the longer shellac resin remains in alcohol, the more water-sensitive it becomes through esterification. Higher shellac ester increases water sensitivity and prevents the resin from drying hard. Long story short, for the most protective and best shellac finish possible, use freshly mixed shellac.

After the shellac has dissolved, filter it through fine-meshed cheesecloth before use to remove impurities. Depending on the level of refinement, some mixtures may not need filtering, but it's worth doing anyway.

Shellac can be applied through many different methods, brush, pad, or spray. A reason for using a thinner cut of shellac is that heavier cuts dry very rapidly and even though it will be dry to the touch within 10 or 15 minutes, wait a while before applying another coat. If you miss a spot, wait for that coat to dry thoroughly before attempting to go over it. I usually don't apply more than three thin coats per day. If you don't allow adequate drying time between coats, the finish may remain soft for weeks.

Temperature and humidity conditions may impact the application and drying times of shellac. During the summer, I'll apply shellac in the cool basement during early morning or late evening hours just to be safe.

Another benefit to using shellac is that it is easy to maintain and repair as new shellac will adhere to old shellac without any problems. Each layer of shellac partially dissolves the layers below it. Water rings can usually be removed by wiping the spot with alcohol or lightly sand the area and apply a fresh coat of shellac.

Application:

• For the first few coats, apply a 1 lb cut with a brush or pad. With either, load the applicator with shellac and run it with the grain from one edge to the other with smooth continuous overlapping strokes.

  • If brushing use a high-quality brush with a chisel tip

  • To make a polishing pad, make a tight ball of gauze or cheesecloth, a little smaller than the size of a golf ball. Then take a 6" x 6" piece of clean cotton and fold the four corners up to meet at the top in a teardrop shape. Twist into a snug ball and use a strip of cloth or string to tie the pad. The pad acts as a reservoir for the shellac.

• Let the shellac cure for at least two hours between coats

• Sand with 400 grit sandpaper

• Vacuum and wipe clean with a tack cloth to remove excess dust

• Repeat the steps above as required. For later coats, use the full 2 lb. cut. I usually use five or six coats for the whole piece and an additional three or four coats for the tops or surfaces that are used more heavily, such as tabletops.

Shell 2 lb. Cut Recipe:

• 1 oz. dewaxed shellac flakes

• 4 oz. denatured alcohol (Lee Valley Shellac/Lacquer Thinner)

• Stir occasionally until all the shellac flakes have dissolved

• Filter through fine-meshed cheesecloth or paint filter before use

• Note: Use a sealed glass jar to mix and store.

Modern Finishes

When extra protection is required, I used a water-based polyurethane finish which is essentially liquid plastic. They provide a decent finish that is reasonably easy to apply and clean up after, just follow the vendor's instructions on the label and don't brush too fast as it can create air bubbles that mar the finish.

Cabinet Finishes

I recently renovated my kitchen and built all new kitchen cabinets. To finish the cabinets I tried Benjamin Moore's Stays Clear acrylic polyurethane for the interior clear finish and Advance paint for the painted exterior parts. The Stays Clear finish looks great when applied with a brush or sprayed. The Advance paint looks better sprayed on, but it needs to be thinned to do so. I used a 20% water to 80% paint ratio and an HVLP 2.3 mm spray gun. Also, the Advance paint has a seven-day cure time which is not ideal under time constraints. Once cured, Advance paint is durable and cleans easily.

UV-cured Paint

For my next painted cabinet project, I will try UV-cured paint. UV-cured paint is a type of paint that uses ultraviolet (UV) light to trigger a chemical reaction that causes the paint to harden almost instantly. Other advantages include a higher gloss finish and resistance to chipping and damage.