Tuesday, March 22, 2011

Wood Finishes & Basic Uses

A very soft "finish" with minimal protective qualities. Best used as a polishing and preserving agent on top of other finishes or as a minimalist finish to preserve the natural color of wood.

Linseed Oil
A natural oil finish made from seeds of the flax plant. One of the least protective finishes but it is easy to apply and yields a beautiful hand-rubbed look. Like all oil finishes, it's best for items that are not subject to a lot of wear and tear.

Tung Oil
An ancient, natural finish made from nuts of the Tung tree. Slightly more water resistant and paler in color than linseed oil. Often used as the base oil component in other finishes. A good choice if you want the hand-rubbed look.

Oil-Varnish Blend
A very popular "hybrid" finish made by mixing a little varnish with a larger quantity of oil. Easy to apply like true oil finishes but with some of the protective qualities of varnish. Group includes antique oil, teak oil, Watco Danish oil, Nordic oil, Scandinavian oil, and various salad bowl finishes.

One of the oldest and most under-appreciated of all finishes. More water and scratch-resistant than oil or oil/varnish-blends but not as protective as varnish or water-based finishes. Also dissolves in alcohol so not the best choice for bar tops. Comes in a variety of colors ranging from nearly transparent to orange/amber and is available in flakes or pre-mixed. Easily repaired and not as toxic as oil-based finishes.

Synthetic cellulose-based finish that is the finish of choice for many professionals. It dries fast, has decent protective qualities (somewhere between oil-varnish blends and varnish), provides excellent clarity and depth, rubs out well, and is fairly easy to repair. It also sprays very easily with great leveling properties. Available in several varieties including nitrocellulose (standard), and catalyzed lacquer (is available with the catalyst added). *see "Conversion" for post catalyzed finishes not used by the average woodworker.

A very protective and durable amber-colored finish that holds up well to wear and tear, water, and solvents. Commonly available in three flavors, depending on the resin used alkyd, phenolic, or polyurethane. Negatives include long curing time, noxious fumes while curing, and poor repairability. Also yellows more over time so not the best choice for light-colored woods.

Good choice if you're looking for a non-yellowing finish that's safer for you and the environment. Decent toughness and scratch resistance but not as resistant to water, heat, and solvents as polyurethane varnish. First coat has tendency to raise grain. Water-based finishes typically cost more than their oil-based counterparts.

Fast curing finish with excellent resistance to heat, wear, and solvents. Typically used for institutional furniture. Highly toxic solvent and formaldehyde fumes -- a professional grade spraying environment is essential. Cellulose Acetate Butyrate (CAB - expensive, tougher, and more resistant) falls into this category. Lacquers made from this very expensive resin are completely crystal clear and non-yellowing.

Wednesday, March 9, 2011

Handcut Dovetails - Why Bother?

Woodworking 101
Handcut Dovetails - Why Bother?
by Paul Rolfe (Sawdust, January 2001)

In Norm Abram's televised world of woodworking, nearly every task is performed with power tools, air tools, and jigs. It is a sharp contrast indeed to the woodworking world of Roy Underhill. On TV, Norm is always very calm in his very tidy shop and his joints fit perfectly every time. On the other hand, Roy is seen sweating, working from a very cluttered workbench and things don't always go together just right; but you get the idea just the same. So, here we have two very different approaches to woodworking. Is one way better than the other? Is one way faster than the other? The answers are maybe, and not necessarily.

Most people will agree that working with power tools, in most cases, is faster, requires less physical effort and produces more accurate, reproducible results. Woodworkers that still use traditional methods will tell you that they get tremendous satisfaction from performing tasks by hand. Using hand planes, handsaws, and brace and bits to shape the wood allows them to hear, feel and understand the natural material that they work with. Nowadays, furniture that is built using traditional techniques is perceived as being of high quality and thus valuable. But it is understandable that not everyone wants to take the time necessary to master the skills required. And then, if someone did have those skills, it just takes too long and too much effort to do things like surface and accurately dimension stock when there are tools like jointers, surface planers, and table saws around.

There is one traditional skill that can be easily learned and used in conjunction with modern techniques. That is cutting dovetail joinery by hand. Yes it does take some practice to get consistent results but it can add so much to a project. If you have a dozen or so drawers to build on a regular basis, buy an Omnijig, it does a fantastic job. But if you are building a blanket chest, jewelry box or highboy, try cutting the dovetails by hand. Why bother you say? I can only say, "Try it and you will see." Routers are very loud and big mess generating tools. In the time it takes to set them and the jig up, you could have been well on your way to getting the joints cut by hand and you wouldn't have had to deal with the noise and mess.

The only tools that you need are a good handsaw and couple of chisels. Other hand tools that are helpful are a marking gauge, and sliding bevel gauge or special dovetail marker. The secret to the simplicity of cutting the joints by hand is that you first cut one side, however you want to, and then use that half to mark the other half. So what if all the tails are not exactly the same size and perfectly spaced, that just adds to the uniqueness and charm of the joints. The only real requirement is that the joints have to fit well, and that comes with practice. So get started and have fun with them!