finishing | David J. Marks

I often get inquiries from fellow woodworkers about finishing products, particularly about the best way to extend the shelf life of various products:

Hello David,

Speaking of finishes, I was never a fan of poly but I tried the wipe on poly you recommended by General Finish. The sealer is very good and lasts a long time in the can, but the other poly products (gloss and semi) coagulate in the can after just a few weeks. Is this normal? Danish Oil, on the other hand, keeps for many months without setting up. One other thought, can the coagulated poly be reconstituted by thinning with mineral spirits? I tried but am nervous about applying it. Thanks for your help.

Regards,

John

Hello John,

General Finishes makes great products and it’s good to hear that you have been working with them. The coagulation’s or “skinning over” in the cans that you have been experiencing is quite normal. This process occurs due to the fact that Arm-R-Seal is made up of a blend of oil and polyurethane as well as solvents and driers. Polyurethane is an “air oxidizing finish” which means it dries by reacting with the oxygen in the air. As you use some of the finish and air begins to replace the loss of liquid in the can, the oxygen in the air, begins to react with the polyurethane in the can and the result is “that gel” that thickens and hardens on the top of the liquid.

My recommendation is to use a product called “Bloxygen” which is an inert gas containing Argon. Argon is heavier than air and when you lift the lid of the can and spray a 4 second shot in there, it will settle on top of the liquid and force the oxygen up to the top of the can. In my experience this product really works well and is worth the cost.

Here is a good YouTube video on Bloxygen:

I would also advise you to dispose of any any cans of finish that have skinned over. Using skinned over finishes is inviting trouble and they most likely will not dry or fully harden. I take my disposable finishes to the Sonoma County refuse area. Check out the attached photos and have fun at the recycle facility if you need to stop there.

Entrance to Sonoma County (California) Refuse Area

Sonoma County Refuse Facility

Things you see at the Sonoma County Refuse Facility

One last piece of advice: always use the gloss finish for building all of your coats. If you want to dull the finish to a semi-gloss or satin, than apply one or two coats of a semi-gloss or satin finish for the last couple of coats. Another method is to use 0000 steel wool and some renaissance wax to lower the sheen and smooth the last coat of finish.

Egyptian Table

Detail Egyptian Table

The finish is usually the last thing that you do when building a piece of furniture, but it is the first thing that someone sees when looking at your work. You can do a great job designing and building a piece of furniture, but if the finish is of poor quality it will devalue the entire piece. Finishes can be divided into two main categories: air oxidizing finishes and solvent release finishes. Air oxidizing finishes cure by reacting with oxygen and this category includes oils, varnishes, and urethanes. Solvent release finishes cure when the solvents evaporate into the air, leaving a layer of resin on the surface. Finishes in this category include shellac, lacquer, and some water based finishes.

No matter which type of finish you select, keep in mind that approximately 60% to 70% of a good finish is surface preparation. That means scraping and sanding until all saw marks, mill marks, etc, are removed. Tabletops are the most critical and need to be examined in raking light. That means placing a light source near the table and positioning yourself so that you can see the light reflect off the top. As you move around, your eyes should be able to scrutinize every square inch of the top, revealing any scratches, flaws, high spots, or low spots.

Generally speaking, I prefer a hand rubbed oil finish for most of the furniture that I build. Linseed oil and Tung oil are the two most commonly used oils in finishes and both of them have withstood the test of time. Linseed oil is derived from the flax plant and has been used since the ancient Egyptians. Tung oil is derived from the nuts of the Tung tree which grows in the Far East and was used to help preserve the Great Wall of China.

Both of these oils penetrate the structure of wood cells creating a finish that is “in” the wood as opposed to being “on” the wood. Applying multiple thin coats will create depth and accentuate the figure of the wood.

Oil finishes do not offer the same resistance to moisture that film finishes like lacquer and polyurethane do, but the trade off is that they allow for a very natural looking finish and permit you to experience the tactile quality of the wood. In addition, they are easy to repair. If the surface looks worn, you do not have to strip it and sand it; you simply rub in another coat of oil. I have also found that they can be enhanced by lightly rubbing with 0000 steel wool and applying a light coat of wax.

Note:

I will be teaching a 5 days hands on class on Finishing in my Workshop/Studio here in Santa Rosa, California on August 1 – 5, 2013.

Finishes that I will cover in the class include: shellac, various oils, as well as lacquers and polyurethanes. For those that have seen Woodworks, I will cover in depth my technique for applying hand rubbed oil finishes which are also known as wiping varnishes.

Here is the link to the Classes Section of my website that gives the class description and registration information.

Finishing Class

Finishing Sample Boards

If you would like to see pictures from previous Finishing Classes I have taught in my Workshop/Studio, here is the link to the Classes Photo Album:

2012 Finishing Class

Finishing Class Pictures

David J. Marks

Woodworking education & inspiration

Tag Archives: finishing

Extending the Shelf Life of Your Finishing Products

Finishing Furniture

Share this:

Like this:

Share this:

Like this: