Preparing Wood for a New Finish - Sail Magazine

Preparing Wood for a New Finish

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The varnisher’s toolkit

The varnisher’s toolkit. Photo by Mark Corke

Often the hardest part of refinishing wood on a boat is getting the old finish off. Unfortunately, there is no magic solution. It usually takes a combination of methods, all involving a large tub of elbow grease and a bucket of patience.
The most basic removal methods, which I will not discuss here, are straight sanding and scraping. Sanding, of course, is needed before a new finish is applied, but is not a very effective finish-removal technique. Dry scraping is best left to professionals, as the potential for damage is extremely high.

Before embarking on any cleaning project, always wear the recommended safety gear, including nitrate gloves, eye protection, cheap rain gear and deck boots. Kneepads are very useful if you are working on a deck. Also, whenever possible, you should remove the item to be stripped or cleaned from the boat to protect adjacent surfaces.
Removing oil from teak

Oil on teak is easy to identify. The wood will look black and dirty, or the finish will be gone completely and the wood will just look gray, or there could be a combination of the two. Oil finishes penetrate the wood and do not form a skin. The discoloration you see is actually mold and mildew that feeds on teak oil. The only way to remove it is with a chemical teak cleaner that will kill the mold and mildew and restore the wood’s natural color.
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One-part cleaners are milder, so I always try these first. They are much gentler on the wood, won’t damage your gelcoat or paint, and are kinder to the environment. First wet the area you wish to clean, then use a spray bottle to saturate the area with cleaner. Work the cleaner into the wood with a bristle brush and let it sit for five to 15 minutes before rinsing it off. While rinsing the wood I use a 3M soft white pad and scrub gently with the grain. This opens up the pores of the wood to get all the cleaner out and ensures the wood is as clean as possible.

If the one-part cleaner doesn’t work, try a two-part cleaner. The first part is an acid that kills mold and mildew. The second part is a neutralizer that counteracts the acid, allowing you to rinse the teak safely. Take special care to keep these cleaners off other surfaces on the boat. Ideally you should protect your topsides with a plastic bleaching skirt. Make sure openings into the boat are sealed, that all lines are removed from the deck and that any vulnerable items, including metal fittings, are removed or carefully wrapped in plastic. You are now ready to begin.

  1. Follow the instructions on the label. If you have gallon containers, it is easier and less wasteful to transfer the chemicals to quart spray bottles
  2. Starting at the highest point of your boat, thoroughly wet the surface with a hose.
  3. Apply part one of the cleaner, spreading it evenly with a nylon pad. Let this sit until it saturates the wood and turns it an alarming shade of black. Then apply a second coat of part one and gently scrub across the grain to avoid raising the pith of the wood; a small nylon toothbrush is great for getting into tight spots.
  4. Push aside most of the black goop and begin applying neutralizer. Gently scrub with a new pad.
  5. Allow neutralizer to sit for around 10 minutes until the wood has turned golden brown.
  6. Finally rinse off all the dirty scum, gently scrubbing as you go. Stubborn areas often require a second application.

Removing finishes with a heat gun

Although it takes practice, I find that using a heat gun is usually the quickest, cleanest and most environmentally friendly method of finish removal. You need a heat gun that heats up to at least 1100 degrees Fahrenheit (anything less is too slow) and an array of scrapers. My favorite is a triangular hook scraper, but it’s good to have a selection for different areas. When scraping, the golden rule is to always use sharp blades.

If you have never used a heat gun, don’t go anywhere near the boat until you have practiced on a less valuable possession! It is easy to scorch or gouge wood. First experiment by holding the gun over wood to the point of scorching it, then see how much pressure you need while scraping to remove finish without causing damage.

When working, aim the heat gun at the wood at a 45 degree angle about one inch from the surface. Heat for about five seconds or until the finish surface starts to bubble—whichever comes first. Aim the heat gun away from the wood and begin scraping by firmly pulling your hook scraper toward you in the direction of the grain. Repeat. As you gain proficiency, you’ll find you can aim the heat gun toward the next section as you scrape the earlier one. This speeds up the process considerably.

Always vacuum up the scraped-off finish flakes as you go. They are a fire risk, and if you let them blow away you could face a pollution fine.
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Removing finishes with chemicals

This method should only be used when a heat gun won’t work and is typically required on more ornate items. The only chemical stripper I would recommend is Citristrip; it works well, is reasonably priced, and removes the dangers of solvent intoxication.
You’ll need Citristrip Stripping Gel, soft toothbrushes, 3M soft Scotch-Brite pads, paper buckets, rags, 3M solvent resistant tape, plastic sheeting and newspaper, paper towels, scrapers, chip brushes, a bucket and fresh water. Be sure to wear safety attire, including nitrate gloves and eye protection, and avoid all skin contact with this product.

  1. Remove the item from the boat or lay down plastic with several layers of newspaper to catch any drips. Be particularly careful when stripping next to painted or varnished surfaces you want to
    preserve; always mask these with 3M solvent-resistant tape.
  2. Apply a liberal coating of Citristip and work it into the surface of the wood using a chip brush or toothbrush.
  3. Allow the stripper to stand for at least 20 minutes until the solution appears dry. Then apply another coat; repeat until the stripper no longer dries out when left to stand for approximately half an hour.
  4. When you think the finish is softened, test-scrape it. If the finish is easily removed, continue scraping, dumping the residue in a paper bucket as you go. Use a toothbrush in hard-to-reach areas.
  5.  Rinse stripping residue from the wood using plain water while scrubbing with a Scotch-Brite pad. Wipe dry with a paper towel.
  6.  Make sure you dispose of your waste properly. Although Citristrip seems fairly innocuous, it is highly illegal to drop it into waterways.

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