Refinishing a Wooden Canoe
by Mike Elliott, Kettle River Canoes
At some point the exposed wood on your wood-canvas canoe will need a complete refinishing job. There are five basic steps in this process:
1. Strip - Before you can bring in the new, you have to get rid of the old, and that means removing the old varnish. There are a number of ways of removing varnish, but I prefer to use caustic chemicals followed by revitalizing the wood with linseed oil. The varnish removal process can be done either with the seats and thwarts left in place or by removing them to give you free access to the hull. If you decide to remove the seats and thwarts, be prepared to replace the existing fasteners as usually more than one of them will be sheared off - albeit unintentionally. Most canoe manufacturers fastened the seats and thwarts to the inwales with bronze carriage bolts, but the Huron Village canoes from Quebec used steel machine screws. Getting at them can be a bit tricky as the inwales were capped with a hardwood strip held down with steel finishing nails. Sometimes, I will keep the machine screws and replace the hardwood strip using brass finishing brads. When I am replacing inwales and decks on one of these canoes, I will discard the hardwood strip and replace the steel machine screws with bronze carriage bolts. A set of 4" 10-24 (3/16") silicone bronze carriage bolts can be obtained from quite a few of the larger canoe supply companies.
Any of the commercial varnish and paint removers will work very well. I get about two gallons of the least expensive stuff at the local hardware store as well as a gallon of mineral spirits. While you are out getting supplies, you will need a few other things if you don't already have them. You will need:
* a pair of neoprene gloves
* a scrub brush
* a couple of putty knives (1-1/2" and 2") to scrape between canoe ribs
* a couple of old paint cans to hold the used remover
* safety equipment for working with caustic chemicals
A pair of canoe cradles makes the job a whole lot easier. Check out the Care and Maintenance article for a construction plan.
Before you start, make sure you have lots of fresh water close at hand. This is not for the canoe, but rather for you in case some of the remover gets on exposed skin. An ounce of prevention is worth a pound of agony due to chemical burns, so wear rubber boots, coveralls and eye protection. If you happen to get remover on your skin or (worst case scenario) in your eyes, immediately flush the affected area with fresh water for a solid minute or two.
If you are doing this job outside, work in a shaded area. It is important to maintain a wetted surface with the remover in order for it to work properly. Work the canoe in sections. In this way, you can keep the remover applied to a horizontal surface. For a typical 16-foot canoe, I do the bottom of the hull in quarters and the sides in thirds or halves. To work on the sides, rotate the canoe in the cradles to get the working surface as horizontal as possible. The basic removal routine for each section goes like this:
* apply remover and let stand for 40-60 minutes. Use the scrub brush to ensure that the area remains wetted. Avoid spreading the remover too thin and use a respirator.
* scrape off the remover into the cans getting as much off as possible.
* remove remaining remover with old rags soaked in mineral spirits. I wear a respirator for this job. The fumes are strong - even outside.
* move on to the next section.
* let stand until dry - usually overnight.
* brush or vacuum the remaining residue from the hull. Most of this residue has crystalized and sweeps away easily, while some is dried to the hull and needs to be knocked off with a putty knife. This is not difficult but it takes time to inspect and clean the entire hull.
This whole process takes a lot of time. Sometimes, I spread this job over several days. In any case, it is not a good idea to hurry while working with caustic chemicals.
2. Bleach - Depending on your canoe, this step may not be required or it can be confined to affected areas on the hull. Bleach is applied to any wood that has been darkened or stained by contact with water. The bleaching can be done with a wide variety of products. Household bleach (sodium hypochlorite) does a great job straight out of the bottle - make sure you are wearing gloves. Two-part bleaches, often sold as teak cleaner, work very well. Infact, they remove all of the color from the wood and you would need to stain the wood afterwards.
I usually use oxalic acid which comes in a crystaline form and is mixed one part acid crystals to four parts water. If you choose to use oxalic acid, remember the axiom when working with acids - ALWAYS ADD ACID. The combination of water and acid generates a great deal of heat. If water is added to acid, the first water coming in contact with the acid can boil almost immediately. The result can be hot acid splashing back up into your face - so take care to add acid to water and thereby avoid this situation. The wood is bathed in the bleaching agent and let stand to dry.
3. Oil - All the mess and bother associated with this process is worth it, in my mind, just to see the wood come back to life with the addition of linseed oil. You will need about two quarts of 'boiled' linseed oil and about a pint of clear wood preservative or mineral spirits. The oil is usually sold as 'double-boiled' linseed oil. The key here is to avoid getting raw linseed oil which would take forever to dry. Boiled linseed oil is not actually boiled. They add drying agents to the oil so that the oil will dry in a couple of weeks.
Mix one part of mineral spirits or clear wood preservative to three parts oil (just like making a vinaigrette for a salad - only don't try to eat this stuff). The mixture spreads better and penetrates the wood better when it is heated slightly. I use a double boiler over an old electric hot plate to heat the mixture slowly and evenly. Again, I wear a respirator to protect against the fumes. Use lots of oil mixture and apply it liberally to the entire canoe - inside and out. There are no points for neatness in doing this. Then stand back and admire your handiwork. Personally, I usually just stand there with my mouth open - perhaps even giggling a little. Once you're done, store the canoe for at least two weeks to dry at room temperature.
4. Shellac - This stage is a well-kept secret in the canoe restoration trade. In fact, it would be safe to say that many people will caution against using shellac as a base for varnish or they will tell you that shellac goes cloudy when it comes in contact with water - not a good thing for a canoe. I looked back at the finishing techniques used by the old canoe builders and found that shellac is an amazing base for varnish. It is easy to use, sands or smooths with steel wool to a fabulous surface, and it dries in about an hour at room temperature as opposed to a couple of days for varnish. I apply three coats of shellac and a coat of varnish in one day, followed by a second coat of varnish a few days later.
Shellac is usually thinned one-to-one with denatured alcohol before applying to the surface. Shellac is anhydrous and will indeed go cloudy when in contact with water. This situation is solved by thinning it with lacquer thinner instead of alcohol. When you think about it, I can't begrudge the varnish manufacturer for insisting on the use of varnish and only varnish for the base coats - it's good for business. That said, your business is the restoration of your canoe and that can be done beautifully with a minimum of fuss and bother by following the methods used when your canoe was built - namely, shellac and varnish.
To shellac the wood, you will need a 2" brush, lacquer thinner, white shellac (shellac flakes already cut with alcohol), 000 steel wool (pronounced 'triple-aught') and a tack cloth. Start by going over all of the wood with steel wool. Then brush and/or vacuum the surface thoroughly before using a tack cloth to pick up any residual dust. Shake the shellac well (shellac that has already been suspended in alcohol) before mixing it one-to-one with lacquer thinner. Apply the shellac quickly and thinly making sure you don't miss any spots. At the same time, don't try to go back over a spot you have already shellacked - it dries very quickly and will only cause trouble if you try 'touch-ups', so apply it and then leave it alone. After an hour or two, smooth the surface with steel wool and apply another coat in the same manner as the previous coat. Cedar tends to absorb a lot of the finish before it starts to 'build' properly and provide an even surface for the varnish top coats, so I apply two coats of shellac.
Clean the brush with alcohol (called denatured alcohol, wood alcohol or rubbing alcohol, it is simply 95% ethanol poisoned with 5% methanol to prevent people from drinking it). Finish the cleaning with lacquer thinner.
5. Varnish - I've read lots of articles about 'The Art of Applying Varnish' and let me tell you, my first attempts convinced me that working with varnish and getting a smooth finish is indeed an art. That is, until I stumbled across the secret ingredient. To get beautiful results with a brush and varnish, the key is to thin the varnish 1:7 with mineral spirits (one part thinner to seven parts varnish) or other suitable thinning agent first.
Start by smoothing the surface with 000 steel wool and cleaning it well with a tack cloth. With varnish, any 2" brush will do as long as it doesn't lose a lot of hair with vigorous use. Work in a well lit area positioning yourself with the working surface between you and the light source. Light reflecting off the wetted surface will show up any spots you missed in the application. Load the brush well with varnish and spread it vigorously over the surface. Grind the brush into the surface to ensure that the entire area is covered. Then with the brush set at a 45-degree angle, lightly 'tip' the surface with your brush. First work across the grain and then do a second pass working with the grain. Don't worry about any bubbles or streaks and don't try to go back over a spot to touch it up. Just tip the varnish across the grain, then with the grain, then go away and leave it alone for two days. When the first coat is dry, go over the varnish with 000 steel wool and a tack cloth, then apply a second coat. A third coat of varnish is applied in the same way and is usually needed to get a smooth, protected finish.
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