Protecting Timber
The environment has a massive effective on unprotected timber, with the sun, rain and pollution causing the most amount of damage. Unfinished and unprotected timber will inevitably weather and depending on the timber type may be quickly or take a number of years.
Under extreme conditions timber will deform, check, split and pull away from fixings. So to protect the timber from the elements of water, cold, heat and ultra-violet light we need to provide a protective finish. Even timber that is kept inside is subject to deterioration and stains so protecting the wood will ensure your project lasts for many years.
Protective coatings perform two tasks; One is providing a barrier to the elements and the other is providing a decorative finish to the timber.
This article will explore the various options for finishing internal timber works such as furniture, chests and tables.
Finishing products are categorised as
- Waxes
- Oils
- Varnishes
- Shellacs
- Lacquers
- Water-based
These different types of products offer different degrees of protection, durability, ease of application and appearance.
Wood finishes come in two different types; evaporative and reactive.
Evaporative
Evaporative finishes include lacquer, shellac and many water-based finishes. This is where the finish dries hard as the solvent or carrier evaporates.
Reactive Finishers
Reactive finishes include linseed or tung oil, catalysed lacquers and varnishes. These finishes also contain solvents that evaporate but they cure by a chemical reaction, either by air or a chemical placed into the finish.
The below table highlights the different types and useage of the various finishes.
|
Type |
Usage |
|
Waxes |
Not an appropriate finish in and of itself. You can use paste wax (carnauba mostly, sometimes beeswax) to polish furniture but only over other finishes, such as lacquer or shellac. |
|
Tung Oil |
Derived from the nuts of trees that are native to Asia but have been cultivated in other parts of the world. Tung oil is available in a pure, unrefined form and in a heat-treated or polymerized form. The heat-treating process makes the oil a bit more durable and speeds up the drying time. It also minimizes a tendency of tung oil to "frost" (dry to a whitish, matte appearance). Tung oil is paler in color and has better moisture resistance than linseed oil. |
|
Linseed Oil |
Unrefined, it's called raw linseed oil, which is rarely used on wood because it dries so slowly. Finishers long ago discovered that by boiling the oil, the resulting product was thicker and dried more quickly. Even though linseed oil that has actually been boiled is still available -- it's called heat-treated or polymerized oil -- most of the boiled linseed oil sold these days is raw oil that has been mixed with chemical additives to speed up the drying time. For wood finishing, you should use only boiled linseed oil. |
|
Varnishes |
Varnish is made of tough and durable synthetic resins that have been modified with drying oils. Labels on cans of varnish will list resins such as alkyd, phenolic and urethane, and the oils used are tung and linseed, as well as other semidrying oils such as soybean and safflower. Varnish cures by the same process as true oils -- polymerization -- but the resins make this finish more durable than oil. In fact, oil-based varnish is the most durable finish that can be easily applied by the average woodworker. Varnish surpasses most other finishes in its resistance to water, heat, solvents and other chemicals. |
|
Oil Varnish Blends |
These mixtures, mostly oil with some varnish added, offer some of the best attributes of both ingredients: the easy application of true oils and the protective qualities of varnish. (Watco-brand Danish oil, teak oil and a number of other finishes fall into this category.) It's difficult to ascribe accurate protective qualities to these products because manufacturers don't usually disclose the ratio of oil to varnish. Oil and varnish blends will dry a bit harder than true oils, and the finishes will build quicker with fewer applications. |
|
Shellacs |
While most people think of shellac as a liquid finish found at a paint store, in its pure form it's a natural resin secreted from a bug that feeds on trees, mostly in India and Thailand. The secretions, in the form of cocoons, are gathered and eventually refined into dry flakes, which are then dissolved in denatured (ethyl) alcohol to make the shellac solution that winds up in cans at the store. |
|
Lacquers |
Most professionals still regard lacquer as the best all-around finish for wood because it dries fast, imparts an incredible depth and richness to the wood, exhibits moderate to excellent durability (depending on the type used) and rubs out well. There are several different types of lacquer, and they exhibit different performance characteristics |
Choosing the correct finish to your woodworking project is essential, by using the wrong type will ruin it.
Comments (1)
you are probably rig
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