Oil Finishes by Richard Colbran
Favourite for woodcarvers:
1. Easy to apply
2. Enhance wood-grain appearance (not always desirable!)
3. Allow control of sheen, according to number of applications
Products
Unlike mineral oils used for lubrication, many vegetable oils oxidise and partially solidify when exposed to air. So when rubbed into wood, they soak in, enhancing the wood grain. It is important to rub off surplus oil shortly after application; otherwise a soft sticky surface may result.
Safety: Linseed oil-soaked rags can self-ignite so after use keep them away from your wood-shavings! Open them out and leave to dry, then bin them or burn them.
Straight Oils
1. Linseed oil – from flax plant
Raw linseed oil slow to cure and not recommended.
Boiled linseed oil usually contains added solvent and metallic salts to speed drying, and is preferable.
PROs – Cheap
CONs – Has yellowing effect on pale woods
Tends to leave a gummy, soft finish
Not moisture resistant and marks easily when wet, so unsuitable for out-door applications
Provides substrate for mildew-growth
2. Tung Oil – from nuts of Tung tree, originally China, but now also South America
PROs – Hard finish
Fair water-resistance (5-6 coats)
No yellowing
CONs – Expensive
Slow-curing
Roughens grain, requiring rubbing down
Tends to show white in cracks and pores
Seldom used alone as finish, but often included as ingredient in high quality varnishes and blended products.
3. Edible oils – Olive Oil, Sunflower Oil etc.
These are often used on kitchen cutting boards, etc, as they are less likely to taint food, and are more of a temporary finish, applied at regular intervals.
Blended Oils
Experiment led to the use of blends of boiled linseed oil, varnish and white spirit (or turpentine) in roughly equal proportions. This was wiped on, left for 20 minutes, wiped off and allowed to cure. Then several more coats applied. However, as soon as the product sits on the surface, rather than soaking into the wood, stickiness presents problems.
Manufacturers have spotted a market opportunity here, and have produced a wide range of blended products with specific names and properties.
Danish Oil, Teak Oil, Antique Oil are products of this type, which are deservedly popular with many carvers, giving good results with little effort. The amounts used are generally small, so cost is not really an issue.
If you use one of these and it produces the finish you need, then there’s no more to be said!
The use of oil finishes for weatherproofing outside work against sun, rain and wind is more problematical, but the growing use of timber for outside decking, cladding and garden furniture has stimulated this market, and new products are around to be tested.
Osmo produce a wide range of oil-based finishes for interior and exterior use, and they have one product- Osmo UV-Protection Oil – which incorporates UV protection and is said to block the usual greying of the wood as it weathers, and it is claimed that it will not crack, flake, peel or blister. If so, then this could well be a winner for outside carvings.