Quick answer: Roslagsmahogny is a traditional Swedish outdoor wood treatment made from pine tar, linseed oil and turpentine. A common recipe uses equal parts of all three.
What is Roslagsmahogny?
Roslagsmahogny is a traditional Scandinavian treatment for exterior timber. It has also been called boat tar or dock tar. The pine tar gives the wood its characteristic warm brown tone and smell, while linseed oil and turpentine make the mixture easier to apply and penetrate the timber.
We have used it on raised beds, fence posts and bird houses. It can also be used on sheds, decks, stairs, boats and other untreated exterior wood.
Roslagsmahogny recipe: 1:1:1
- 1 part 100% pine tar
- 1 part linseed oil
- 1 part genuine turpentine
Our original mixture used boiled linseed oil. A current recommendation from Swedish tar specialist Claessons Trätjära uses cold-pressed raw linseed oil instead, because raw linseed oil penetrates the timber more readily. Both versions exist, so check the instructions for the products you are using.
How to apply it
Brush dirt and loose material from the wood. Stir the mixture thoroughly and apply thin coats with a brush. Very absorbent end grain may need additional treatment. Drying time varies substantially with temperature, humidity, timber and coat thickness, so allow several days before walking or sitting on treated surfaces.
Important fire safety
Linseed-oil-soaked rags can self-heat and ignite while the oil oxidises. Never leave oily rags crumpled in a combustible place. Follow the product safety instructions and local disposal guidance.