Monthly Archives: December 2010

Finishing for Non-Finishers, Part V

Before you begin…STOP!

Careful assembly and surface preparation go a long way to making your finishing techniques pay off.  Said differently, no finish can (or will) cover up every blemish you might leave by not preparing the surface carefully.  In fact, most experienced woodworkers would agree that applying a finish tends to magnify poor surface prep rather than conceal it.  That’s why the first four posts in this series haven’t talked about actually applying the finish.  And that’s why this one starts the way it does.

It’s not too late.  You can still give the surfaces one last, careful examination before you start with the finishing.

Okay, Here We Go

Get out the Sample Boards

Once you’re certain all of the blemishes, scratches, swirls, glue squeeze-out and the rest of it are gone, (and this includes your sample boards, by the way) it’s time to work out your “finishing schedule”.  That’s my term, and it doesn’t imply the timing of the steps, but rather the steps themselves.  And all of the work is going to get done first on the sample boards you’ve saved from the project. While it might seem like a ton of additional effort, working out your finishing steps on project remnants will pay dividends in several ways.

First, it saves the project from ruin.  Unless you have used the proposed sequence of colorants and topcoats before, you don’t really know how they will look on your finished project.  The worst possible outcome is that the finish doesn’t provide you the look you had in mind when you began, or that the finish really does damage the appearance of the project.  In the latter case, I refer to instances like pigment stains on pine, or certain oils on cherry, both species that are prone to significant blotching.  If blotches are the look you’re after, terrific – but better to know your wood is going to react this way before hitting the actual project with the stain.

Second, as you build up your finishing samples, you’re building a library of sorts.  Assuming you keep clear notes about your finishing sequence (more on this in a minute) you can refer back to your library when you’re working on the next project and pick out a sample that offers you the look you’re after.  You will build up familiarity with different finishing products and determine what works well in your own shop.  Here is an assortment of the sample boards from my shop, front and back:

Finishing Schedule Notes

There are any number of ways you can record the steps you’ve taken as you develop your finishing schedule.  Use note cards, a spiral-bound notebook, or do what I do:  record your work directly on the back of the sample.  No matter how you record your work, write down every step in detail.  A small detail like a change in sanding grit can make a difference in your end result.  One small shortcut is to develop shop standards – steps that you perform the same way each and every time you execute them.  For example, in my shop, “scuff sand” means P320 grit paper held in my hand.  So I save a few pen strokes there.  Recording the process on the sample saves me from searching through the shop for the particular card I need to re-create a finish.

At the beginning of this series, I suggested that the time to chose a finish was before you started work.  If you have done that, you’re ahead of the game. If you haven’t yet made those decisions, now’s the time.  Since this series is aimed at non-professional finishers and woodworkers, my advise is to keep things simple at the beginning.  That’s why plain shellac is the first finish I’m going to suggest you get acquainted with.

Getting to Know Shellac

As a top coat, shellac has a lot going for it, which is why it has been around for so long.  It’s natural and non-toxic.  You’ve probably eaten it more than a few times: ever wonder what makes the outside of M & M’s so smooth and shiny?  You’ve probably seen someone wearing it in their hair, too.  Ever wonder what finish preserves the American furniture in the Smithsonian?  There are a lot of reasons its popularity has lasted.  I recently grabbed a few apple boxes from my local grocery store, and guess what is printed on the bottom!

A family-friendly finish....

For the beginning finisher, shellac has a number of other benefits.  Because its solvent is alcohol, each succeeding coat dissolves the preceding one, and they essentially “melt” together.  So as you add coats, you’re really not building one coat on top of another with discrete borders in between.  Instead, you’re just making one layer thicker and thicker.   If you decide that you have really messed up the job and need to start over, a thorough soaking with alcohol will return the shellac to solution and you can wipe it off the surface and start over.  This means that the finish is easily repaired, too.  Of course, being alcohol-soluble has at least one strong drawback: if you spill an adult beverage on this finish, it can be damaged unless you clean it up immediately.  Clearly this could be a limitation for a tabletop, but for boxes, bedroom furniture (dressers, bed frames and so on) shellac might be all you need.  Finally, because you aren’t using any drying oils, there is no risk of spontaneous combustion from oil-soaked rags.  You do, however, want to provide plenty of ventilation to disperse the alcohol fumes, which are flammable and can be explosive in high enough concentrations.

Shellac has several other useful properties that endear it to finishers, professional and amateur.  Diluted concentrations of shellac are often used as a “wash coat” on bare wood.  Depending on the amount of shellac dissolved in the alcohol, the “wash coat” controls (limits) the amount of coloring or penetrating finishes (like oils and pigment stains) that will absorb into raw wood.  For those blotch-prone species like pine and cherry, a dilute coating of shellac goes a long way to eliminating the problem.  More on this later in the post.

In the same way that shellac helps to seal bare wood, it can provide a barrier between different steps in a finishing sequence.  Say, for instance, that you have dyed a project with a water-soluble dye, and being environmentally friendly,  you decide to use a water-based topcoat.  A seal-coat of shellac in between the dye and the topcoat will prevent the water in the topcoat from re-dissolving the dye.  The uses go on and on, and your continued research and experimentation will produce more than I can write about here.

The November/December 2010 issue of Fine Woodworking magazine has a good article on the origins and processing of raw shellac.  It’s interesting reading.  For the purposes of this article, I’ll summarize and condense some of that information and more into a few short paragraphs.  The article is worth the read, if you have time and a subscription.

Raw shellac includes a component of wax, which all by itself is of no concern to a finisher.  However, when shellac with wax is used as an undercoat to some other finishes, there can be a problem with the succeeding layers adhering.  To address this issue, shellac manufacturers have “de-waxed” and then dried shellac into flakes that you can dissolve in alcohol, making your own concentrations of shellac as a finish right at home.  Along with the dewaxing process, the color of the flakes can be controlled, giving you the option of colors ranging from a warm honey-amber hue to nearly colorless.  These options provide you with a lot of control over how the shellac looks on the project.  Shellac can also be tinted, giving you even more precise control.  In its colorless state, it will do little to change the color of the project.

Shellac’s concentration is measured in the number of pounds of shellac dissolved into a gallon of alcohol.  This concentration is referred to as the shellac’s “cut”.  One pound of shellac flakes dissolved in one gallon of alcohol is known as a “one-pound cut”; two pounds as a “two-pound cut” and so on.  The amount of shellac in alcohol is an important factor for a finisher.  The more shellac in the solution, the more you’re applying with each coat and therefore the fewer coats you’ll need to build up the same film thickness on the project.  There is a drawback to using higher cuts of shellac: the higher the concentration, the harder it is to put on a streak-free coat by hand.  A three-pound cut is about as high a concentration as you’re likely to find, or want to mix yourself, and I think you would have better initial luck with a one- or two-pound cut.

Before you decide to start mixing your own finishes, here’s a time-saving suggestion.  Buy a quart (or a gallon) of a product called Seal-Coat, made by Zinsser.  This is a dewaxed shellac in a 2-pound cut, and it does a great job as that “barrier coat” I mentioned a few paragraphs above.  Finishers refer to this barrier as a “wash coat”.  If you’re going to apply a wash coat, dilute some Seal-Coat with an equal amount of isopropyl alcohol, which you’ll find at paint stores and in the paint departments of the big box stores.  Brush the mix on with a natural bristle or Taklon-bristle brush.  Work “off” the edges (in other words, start your stroke a few inches in from an edge and brush off the surface) and keep a wet edge.  Don’t rebrush or try to “tip off” the shellac – put it on and leave it alone.  When it’s dry (allow half an hour) gently scuff-sand the surfaces with P320 grit sandpaper, and you’re ready for the next step in your finishing schedule.

Shellac can also be used all by itself – not as a wash coat, but as the entire finish.  As I mentioned, it’s been used as a finish for hundreds of years.  If you plan to use shellac as the only finish for your project, it’s time to consider mixing your own.  More on that subject in the next post.

So, on your sample boards, either tape off sections or use a table saw, radial arm saw or cutoff saw to cut kerfs across the width of the sample.  Apply a thin coat of your shellac to all but one end section of the sample board.  The end section will be used to judge your first color layer without the benefit of a wash coat.  The rest of the board will start with the wash coat as the first step in the finishing sequence.

In the next post we’ll talk a little about color and the use of shellac as a final top coat.

Here are links to the first four posts in this series.

Finishing for Non-Finishers, Part I
Finishing for Non-Finishers, Part II
Finishing for Non-Finishers, Part III
Finishing for Non-Finishers, Part IV

Jeff Zens owns and operates Custom Built Furniture in Salem, Oregon.  He is a frequent woodworking instructor and writer.

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