As I am finishing my Don Hill style 16'er I noticed that I am getting some mildew growing on the Teak oil finished ribs. The ribs have 2+ coats of Teak oil. The boat is stored in an open two car garage, no doors.

Does anyone know if boiled linseed oil is any better at preventing mildew than Teak oil?

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Hi John,
It may help if you give information about your location.
The solution may depend more on location rather than oil.

I live in Southern CA, with about 8-inches of annual rain. Mold or mildew is hard to grow unless you have a boat in a marine environment with closed hatches.

Have you tried cleaning / killing with a dilute bleach spray (10-20 percent), drying well, and keeping it ventilated?

What is your typical humidity?


I live on the Olympic Peninsula across the Hood Cannel from the Olympic mountains, NW Washington state. I know, rain forest.

I have no direct experience with your specific application, but I have some general suggestions that may guide your thinking.

Have you checked your storage area for sources of existing mildew? If you are ignoring the source, any actions will be short-lived.

The amount of applied oil and wipe downs may have to be adjusted. After your application, maybe the excess oil needs to be removed sooner.

Finally, paint stores and hardware stores used to sell additives to paint used in bathrooms to help control mildew. I am sure there was some toxicity involved to kill the mildew. There may be a current version of chemical death that you can add to the oil.

As soon as someone gives better suggestions, be sure to ignore these.


John:  The Wooden Boat Forum had a guy that had "mold" on the outside of his log home.  He applied a mixture of borax and propylene glycol to cure the problem .  No other info about how to dilute/proportions etc.  Try it on a rib and see what happens.  Ethylene glycol(antifreeze) might work as well. 

I use the boiled linseed oil/turps/japan drier mix on the stairs from the cottage down to the beach  and have not had a problem with mildew.  It will darken the wood over time but  this might be oxidation of the mix as well as UV degradation.  One of my kids has a Phd in chemistry and will ask him if any of this makes sense. These Cal Tech guys have opinions on everything-right or wrong!

Good Luck

To solve the same problem on CVG doug fir gunnels I cleaned them up with 10% bleach solution and then varnished. Any mildew can now be cleaned off with soap.

I live in the northern Cal redwoods and we get mildew on everything.

I had some issues with mold on a boat that I used penofin marine oil. It was the one year I stored the boat outside under a cover in winter. It took a lot of work to remover he mold and I tried many things. Dilute bleach killed the surface. Mold but mildew is a fungus and so it attaches deep into the wood. If you don't kill the source it just comes back. I bet an over the counter mold remover from the hardware store would work really well. I ended up using tsp , that mostly removed the oil from the wood. Then I used oxalic acid to bleach the wood. I then re oiled. The areas I repaired ended up much darker than the rest. So I would probably shy away from the tsp and try to the bleach route and Mabye reoiling with a coat of oil laced with additional driers to keep mold at bay.

It's interesting the teak oil is molding. I always thought linseed oil was the more likely culprit for mold due to it being derived from flax seeds which are high in fats that provide food for mold. I guess I always assumed teak oil was less prone due to it due to its makup.

Worth noting was that when I got the boat into a covered area for storage and started leaving it there without a cover on most of the time, all my mold issues went away. I feel like he cover was most likely trapping in that humid area and providing a ripe place to grow mold. I think you can probably get rid of most of your mold with bleach, but you'll want to try and address the issue of why is it molding if you want to keep it from constantly coming back.

Update; I wiped "30 seconds" straight from the jug with a paper towel on the ribs. Mildew disappeared, good as before. I am going to try the LVT, linseed/varnish/turpentine mix to see if this will end the mildew. If it does not stop the mildew "30 seconds" will have a place on my drifter.

Hey John,

I had a similar experience with Watco teak oil (only time I ever used it). Before and after I always use Daly's teak oil with no issue. If you go the LVT route you may want to throw some Japan drier in a well.


Well well, what do you know Watco teak oil is the same oil that is mildewing on my boat. I will look for the Japan dryer.

I have all of the players ready. Is the LVT mix equal parts of each w/Japan dryer as listed in the can?


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