Boat Soup and Launching
The traditional finish for a Scandinavian working boat is pine tar thinned with linseed oil and turpentine, brushed on hot or warm and renewed every year. Mystic Seaport's recipe, what kiln-burned and dark pine tars are, the first soak, the launch, and how a dry-planked clinker boat swells tight.
- 3 min
- 5 steps
- 2 questions
- Lesson 127 of 204
In this lesson
- Boat soup
- Launch
- Every spring
- Try it
Picking up where you left off.
What you need
| Have it | Material | Spec | Qty | Where to get it |
|---|---|---|---|---|
| Pine tar | Kiln-burned pine tar (golden, ‘peasant tar’ grade) or a dark Stockholm-type tar | 1/2 pint per batch | National Historic Ships UK (Mystic Seaport) | |
| Boiled linseed oil | 1 quart per batch | Hardware or paint store | ||
| Pure gum turpentine | 1 quart per batch | Art or paint supplier | ||
| Japan drier optionalSpeeds drying above the waterline; leave it out below. | 1/2 pint per batch | Paint supplier |
Tools
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North House’s older pram classes finished their boats with pine tar, linseed oil, and turpentine 1, the classic Scandinavian working-boat finish. It soaks into the wood rather than forming a film, smells wonderful, and is renewed each spring.
Boat soup
Mystic Seaport’s recipe, published by Theodore Kaye 2:
- 1 quart pure gum turpentine
- 1 quart boiled linseed oil
- 1/2 pint pine tar
- 1/2 pint Japan drier
Below the waterline, Kaye gives equal thirds of tar, oil, and turpentine with no drier 2.
Pine tar comes in grades. Kaye describes the Swedish maker Auson’s dark tar, a byproduct of charcoal burning, and its golden kiln-burned tar made from resinous stumps, sometimes called peasant tar 2. The lighter tar gives a honey-colored finish; the dark one goes nearly black over time. Stockholm tar is the historic name, from Sweden’s export trade 2.
Warm the mix in a pail of hot water (never over a flame; turpentine is flammable) and brush it on generously inside and out, working it into the laps and end grain. Let it soak, wipe off what stays on the surface after an hour, and repeat over several days until the wood stops drinking.
Linseed oil generates heat as it cures, and crumpled oily rags can catch fire on their own. Spread them flat outdoors to dry, or keep them under water in a closed metal can.
Quick check
Mystic Seaport adds Japan drier above the waterline.
Quick check
Spread them flat to dry outdoors or keep them under water in a closed metal can.
Launch
A riveted clinker hull built of dry boards will weep at first. Put it in the water, let it sit, and the planks swell against each other and the laps close up. Bail as needed for the first day; if a lap still weeps after a few days, check it for a missed or loose rivet.
The finished boat is versatile. North House notes the method adapts to sailing and iceboating as well as rowing 3; the pram Phil Winger built in Minneapolis later carried a hand-woven wool sail coated with pine tar and tallow 4.
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Every spring
Scrub the boat, let it dry, and give it a fresh coat of boat soup before launch. A pine-tarred boat ages to a deep amber, and each coat feeds the wood instead of building up a skin to peel.
Try it
Mix a half batch and test it on an offcut of your plank stock. Watch how many coats the end grain takes, and how the color deepens in the sun over a week.
Lesson complete
Nice work.
Sources for this lesson
- 1Caleb Mattison. Pram build. North House Folk School blog. 2015. verifiedJune 12, 2015. A pram from John Beltman's class, white pine and oak, secured mostly with copper rivets, later fitted with mast, daggerboard, and rudder. Older North House pram courses used white spruce, white pine, black ash, oak, and copper fastening, finished with pine tar, linseed oil, and turpentine.
- 2Theodore P. Kaye. Pine Tar: History and Uses. National Historic Ships UK (Mystic Seaport). 2011. verifiedMystic Seaport's soak: 1 quart pure gum turpentine, 1 quart boiled linseed oil, 1/2 pint pine tar, 1/2 pint Japan drier; below ground, equal thirds and no drier. Stockholm tar history; Auson grades: 588 dark (charcoal byproduct), 773 golden kiln-burned stump tar.
- 3Building the Norse Pram: Intro to Lapstrake Construction. North House Folk School. verified7 days; instructors Brian Thorkildson and Phil Winger. Group builds an 11-foot wooden rowing pram with lapstrake techniques and beveled watertight planking; compound bevels for framing, riveting planks, and trunnels to fasten frames. No-mold construction from readily available lumberyard lumber with minimal tools including carving knives; adaptable to sailing, iceboating, and rowing positions. Required tools: sloyd knife, 10-16 ft tape, pencils, safety glasses and hearing protection; optional block plane and spokeshave.
- 4Martha Brummitt. Building a Norwegian Pram and Weaving a Wool Sail. Norwegian Textile Letter. 2019. verifiedFebruary 26, 2019. A pram built with Phil Winger in Minneapolis: 11 ft 7 in long, seats up to three rowers, of pine, walnut, and Douglas fir with about 500 copper rivets, by hand tools; a woven wool sail coated with pine tar and tallow.