COMPLETE GUIDE TO WOOD FINISHES

If you are an amateur (or even professional!) woodworker, or simply someone who works on furniture or wood projects as a hobby, you would have had the age old dilemma of which wood finish to apply to your projects. Unfortunately, the information in and around the web is very varied, with different opinions voiced by professionals across the board. With that in mind, we undertook a review of as much information we could get our hands on to put together this guide on Wood Finishing.

WHY FINISH WOOD?

If you don’t want your wooden furniture, floors or projects to deteriorate, then finishing is absolutely essential. A good finish will stop wood from:

• Drying
• Cracking
• Swelling and shrinking due to weather changes
• Simple damage (such as usage scratches)
• Stains (accidental)

The key is to remember that you need to understand that advice varies based on the type of wood, the nature of the item, for example floor finishes vary greatly from furniture finishes. Antique furniture finish requires very careful consideration and surfaces for food preparation or consumption ought to be “safe” for use.

THE BASICS OF WOOD FINISHING

Contrary to popular belief, the process of wood finishing actually starts with preparing the wood surface for the final finish to be applied and that process typically involves some sanding. (You can sand suing a number of methods and tools which we cover elsewhere). If finishing wooden flooring, you may want to consider commercial sanders and buffers.

After sanding and getting the surface right, you would have to “prime” the surface, for example unintentional imperfections on the surface such as holes from knots or nails. You could fill these gaps and holes by the use of wood putty, wood fillers and in cases of larger holes a combination.

If you want to change the color of the wood surface, then the next step would be to use a range of wood coloring techniques, from wood staining to bleaching. (those of you who are “antiquing” furniture may want to apply your chalk paints at this stage. If you want to aim for “natural” colors you might skip this step and aim for a colored finish such as colored wax.

It is at this stage that you need to consider your finish. Depending on the type of effect you are aiming for, you can now apply the best finish for the job.

This isn’t the end though! You may want to finalize your effect especially if you would like a shiny finish – which means you should now aim for buffing. There are a range of buffing tools and finishing materials you can use such as Tripoli polish (or rotten stone) to steel wool.

DIFFERENT  TYPES OF WOOD FINISHES

Wood workers and furniture makers classify most wood finishes in one of five groups, which are broadly explained by the nature of the finish. These may overlap, or a finish may be classified in more than just one of the categories below:

• Penetrating finish
• Surface Finish
• Evaporative finish
• Reactive Finish
• Coalescing finish

EVAPORATIVE FINISH VS REACTIVE FINISH

This distinction is based on two factors, the rate of drying and the type of cure.

Most evaporative finishes have solvent or distillates that evaporate and leave the actual residue. Wax would be the best example of an evaporative finish.

The key distinction of a reactive wood finish is that it changes its chemical composition as it cures the wood, even if they have solvents or distillates as part of their base. Oil finishes such as tung oil and other oil based varnishes are part of the reactive finish families.

COALESCING FINISHES

This type of wood finish tends to be a combination of evaporative and Reactive finishes, and most often tend to be a water based finish such as water-based polyurethane. Their primary feature is that they are comprised of slow evaporating thinners (water) and the solvent tends to be glycol ether.

PENETRATING FINISH VS SURFACE FINISHES

The simplest way to distinguish between penetrating wood finishes from surface wood finishes is to understand how they work. Simply put, a penetrating finish does exactly that, it “penetrates” the wood and dries inside the wood, while a surface finish stays on the “surface” and dries on the top layer of the wood.

The key here is to remember that most penetrating finishes offer a more natural look to your furniture and wood projects. They tend to seep deep into the wood grains and tend to go hard. Most oil finishes fall into this category. They are very easy to use.

Surface finishes tend to be longer lasting, however not all surface finishes give furniture natural look and feel. Most waxes, varnishes, shellacs fall into this category.  The largest benefits of surface wood finishes are the protective quality of them. They tend to be stain and water resistant and protect your wood pieces for much longer.

SIMPLE COMPARISON TABLE OF TYPES OF WOOD FINISHES

Common Finishes	Type of Cure	Type Of Action
Shellac	Evaporative Finish	Surface finish
Lacquer	Evaporative Finish	Surface finish
Oil Varnish	Reactive Finish	Penetrating Finish
Water based	Coalescing finish	Penetrating Finish
Conversion	Reactive Finish	Penetrating Finish
Wood Oils	Reactive Finish	Penetrating Finish
Wood Wax	Evaporative Finish	Surface finish

PICKING A WOOD FINISH

There are many reasons for picking one finish over the other, however the most common reasons are:

• What the end appearance is supposed to be.
• Usage of final product and level of protection required
• How easy it is to apply (some are easier than others)
• Level of buffing required (you cant really buff or rub some finishes well, while others, especially surface finishes, tend to buff quite well.)
• How safe the finish is (before, during and after application). Some finishes for example are quite toxic and shouldn’t be used in a home environment, while others are relatively safe to use.
• Costs – after all, you may want a fantastic finish, but if you are working within set budgets, you should only buy what you can afford!