Polymerized linseed oil (stand oil)

Overview

Polymerized linseed oil, also called stand oil or heat-bodied oil, is linseed oil that has been heated, in the classic process for days near 300 C without air, until its molecules partly link up. Wikipedia describes the result as viscous, forming more elastic films with less yellowing than raw oil. Because the chemistry is done in the pot, it needs no cobalt or manganese driers to dry. It is the base of several modern "natural" wipe-on finishes, and it is what many woodworkers reach for when they want the look of linseed without the weeks-long cure of raw oil.

Pros

• Cures in hours to days per coat, much faster than raw oil, with no metallic driers (the maker states this for its products).
• Less yellowing and a harder dried oil film than raw linseed, per Wikipedia.
• Easy to wipe on; forgiving and easy to repair.
• Low odour compared with solvent-heavy blends, and the maker reports zero VOC for its products.

Cons

• Still a thin, penetrating finish: modest wear, water and heat resistance.
• More expensive per square foot than hardware-store boiled oil.
• Over-application stays tacky; the maker blames long cures on oversaturation.
• "Polymerized" is a brand description, not a standard; check each label for what else is in the can.

Suitability

Works well on White oak, Hard maple, Black walnut, European walnut and Black cherry, where a clear, natural look is wanted on furniture, shelves, toys and cabinet interiors. On very oily woods (Teak, East Indian rosewood) cure can be unreliable; wipe with solvent and test. Not suited to exterior use or to hard-wearing floors and counters.

Coats and application

Sand to 180 to 220 (Sanding schedule). Tried & True's instructions for its Danish Oil are to apply, wait 5 minutes and wipe dry, burnish with 0000 steel wool before every coat, and allow at least 8 hours of cure; Original Wood Finish and Varnish Oil call for 60 minutes of penetration and at least 24 hours of cure, with Original limited to 3 coats. The maker quotes coverage up to 1000 sq ft per gallon, says not to use a brush, and warns against mineral-oil polishes before or after. Example schedule: coat 1, wait 5 minutes, wipe dry, wait 8 hours; coat 2 the same; coat 3 optional; wait several days; light wax if wanted.

Compatibility

Polymerized oil is compatible with its own family: more oil, or a paste wax (Paste wax) after cure. Test before adding oil-based varnish on top. Water-based finishes will not bond well to a fresh oil. Dewaxed shellac (Dewaxed shellac) is a more reliable barrier to later coatings. It will darken a stain slightly. Compare Boiled and raw linseed oil, Tung oil and Oil and wax blends.

Care and repair

Re-oil worn spots; there is no film to strip. The maker says the finish is water-resistant, not waterproof, and that the oil has no known shelf life (a skin that forms in the can can be scooped off). Wipe with a damp cloth; avoid harsh cleaners. For heavier damage, sand and re-oil.

Safety and environment

Oily rags can heat and ignite by themselves. The USDA Wood Handbook says to immerse them in water and seal in a water-filled airtight metal container; Tried & True's FAQ says to put them in a jar or bucket of water and then seal; read the label. See Oily rag safety.

Food contact is a claim to read carefully. Tried & True states that its products comply with FDA 21 CFR 175.300 as "safe for food contact surfaces" and markets Danish Oil for salad bowls and butcher blocks. That is a manufacturer statement; 21 CFR 175.300 lists permitted ingredients (linseed oil is on its drying-oil list, which may be raw, heat-bodied or blown) for resinous and polymeric coatings acting as a barrier on food-contact surfaces. It does not itself certify a finished wood item. The Wood Handbook advises checking the label, the manufacturer or FDA for any finish used on food items. See Food-safe finishes. Gloves are optional per the maker but can reduce skin dryness.

Related

• Boiled and raw linseed oil: cheaper, with driers.
• Danish oil: other oil-varnish blends sold under the same name.
• Oil and wax blends: oil plus wax in one product.
• Wipe-on application: wipe-on technique.
• Oily rag safety: fire hazard.