Phoenix's New Cabin Sole Part 3: Sealed and Protected with Tung Oil

With our teak and white oak cabin sole installed, the next big hurdle was deciding on the type of finish we wanted to use on it. One thing that we knew for sure was that we didn't want anything that would be slippery or with a high gloss finish.

Teak and white oak cabin sole installed and ready to be finished

We've been on many production boats over the years, and slippery cabin soles are a definite no no. We're also not fans of high build finishes on teak -- we want our wood to actually look and feel like wood, not plastic. The aversion to high gloss is more of a personal preference -- we've used a satin finish throughout Phoenix, so a high gloss floor just wouldn't do.

Once upon a time there was an oil-modified urethane that boaters loved called Ultimate Sole; if they still made it, we probably would have used it. We looked into several gym floor finishes that are often used on basketball courts; however, the vast majority are now water based urethane finishes that aren't compatible with oily woods like teak unless you first wipe the wood with acetone, then seal it before finishing -- much more work and expense than we were looking for. Our friends Chuck and Susan recommended a product called Fabulon, which is a bowling alley finish that they were very happy with; however the non-slip bowling alley version is also only available in a high gloss.

There was also the consideration of touching up the wood down the road, and urethane finishes and varnishes aren't very easy to touch up without sanding and stripping. This led us to look at penetrating oils and waxes, and after pulling and reviewing the MSDS for several products we learned that they were simply either carnauba/parrafin cut with solvents or resins, or tung/linseed oil cut with solvents or resins.

In fact, products like Waterlox, "Danish Oil", or "Modified Tung Oil" are really just proprietary "spar varnishes" -- or mixtures of oils (~10% or less), resins (alkyd, phenolic, or urethanes) and solvents (mineral spirits, Naptha, or paint thinner (~60% or more of the formula)).  Most of these finishes are rather pricey, and given the chemical make up, we weren't very impressed. Pretty expensive paint thinner, if you ask us!

Ultimately, we opted to do a traditional tung oil finish (not to be confused with modified tung oils). Tung oil is a polymerizing oil but it needs solvents to penetrate into the wood rather than create a surface film. The main difference between a traditional tung oil finish and a modified finish or spar varnish is that you leave out the resins.

With the help of a solvent (mineral spirits), tung oil will penetrate and polymerize in the wood, giving it a flexible, waterproof finish. It cures to a matte finish, and won't peel or crack like urethanes. Unlike linseed oil, it will not attract mold or go rancid. Plus, touch up is easy -- periodically (maybe once a year for high traffic areas) wipe your tung oil/solvent mix on any worn areas with a lint-free rag.
 
Tung oil does not have UV inhibitory characteristics, so we wouldn't recommend using it on exterior wood unless you make your own spar varnish and blend it with a resin with UV inhibitors (pigments). However, for interior projects, it met all of our criteria (non-slip, not shiny, easy to apply, easy to care for and touch up, cost effective).

We purchased pure tung oil from Real Milk Paint and mineral spirits from our local hardware store. Real Milk Paint sells a citrus solvent that we would have used if we were living on the boat while finishing it (and we'll probably use this down the road for touch ups), but since we're not there yet, using mineral spirits was less expensive.

The owner of Real Milk Paint suggests a 1:1 ratio of tung oil to solvent for most woods, but a 1:2 ratio for dense woods like teak and white oak. We played with some test pieces before we got started, and decided that a 1:3 ratio of tung oil: mineral spirits gave us excellent penetration without darkening the wood too much.

Application was pretty easy. First, we used a random orbital sander to sand the entire floor with 120 grit paper, then vacuumed, wiped down with mineral spirits, followed by a tack cloth. We purchased a lambs wool applicator that we could attach to a mop handle, poured our tung oil/solvent mixture in a paint tray and mopped it on. The key was to get the maximum amount of tung oil to penetrate the wood in a short period of time -- basically keep the wood wet until it was saturated and would not absorb any more oil. (Safety Precautions: apply in a well ventilated area (exhaust fans in hatches), wear solvent rated masks (not dust masks), wear chemical goggles and nitrile gloves.)

The wood soaked up the first coat of tung oil pretty quickly, roughly 10-15 minutes after it was mopped on. The subsequent coats took longer to absorb, and I periodically mopped more oil on any areas that were absorbing the oil faster than others to get even coverage. Each cabin took 3-4 coats before the wood was saturated (oil remained on the surface and it looked wet/glossy for 45 minutes).

Two coats of tung oil on the foward cabin sole -- wet but not saturated yet

We wiped up the excess oil with old t-shirt material, and periodically went back over the wood with the cloths to mop up any oil that seeped out of the grain for the next 48 hours. We "skated" along the cabin sole with old t-shirts under each foot to make the job easier, and to gently buff the floor.

Excess tung oil wiped off of the forward cabin sole and ready to cure

Given Phoenix's size, we broke the job up into two days. On the first day we finished the head, aft cabin and forward cabin. The following day we tackled the main cabin.

The most difficult part of the process was having the patience to allow the finish to cure. Tung oil cures by oxidation and we needed plenty of ventilation to remove the solvent, so we had fans running to help speed the process. Initial cure is 10 days; with a full cure after 15-30 days, depending on the temperature.

Main cabin

Galley

Looking forward from the main cabin

Aft cabin

Hatch boards in the aft cabin

We wore Tyvek booties for a month and were careful to keep excess dirt/debris off of the floor. Once the tung oil had fully cured we were finally ready to get Phoenix out of construction mode and get her ready for the sailing season!