Bulkhead finish recommendation

[n5ama]

My Contessa 32 has teak bulkheads, cabinet doors etc. They are generally in great shape but since moving the boat from the state of Maine to (on the hard and wrapped during the winter) to south Texas (in the water and warmer all winter), I see some light mold/mildew forming especially on the lower surfaces

What would be a good treatment/preservative to put on the interior surfaces to address this issue? I’m really not interested in a varnish or anything that will dramatically change the color or shade. Is there an oil treatment that can be used here? I’ve read in past responses to this problem that say oil promotes mildew growth and that is counter to what I want to do.

Thanks in advance for any help,
Tom

[JBP]

While the boat is in use or in storage?
If it's in use, you can wipe down the surfaces with Concrobium or a DIY version of Concrobium
https://www.practical-sailor.com/blo...at-really-work

If it's in storage, dehumidifier or desiccant (Damp Rid) can help. You can also get chlorine dioxide (poisonous) packets.

MDG Chlorine Dioxide Odor Control

[JPA Cate]

My experience with oiled surfaces was that they grow mold very well. If you want to retain the oiled surfaces, you can also make up a spray of water with clove oil 10 drops to 1 liter, spray it on, let it set an hour or so, and wipe it off. The clove oil is reputed to kill the mold spores, so the surface will stay clean till more settle on it.

I chose to shift to matte varnish finish, which I only had to dust occasionally, and left the teak looking (to my eye) quite nice. Ymmv. On that boat, all the interior teak was matte, except for the high wear areas, which were very high gloss, because the matting agent makes it less durable. It was an understated look, but nice and clean looking.

Ann

[Iron E]

Originally Posted by JPA Cate

My experience with oiled surfaces was that they grow mold very well.

Ann

Yep. Teak oil is like Mold Fertilizer. The only part of our boat that was oiled was the eyebrow, which turned into a gross, black, moldy trim.

Personally, I would varnish the bulkhead, it will last for many, many years since it's inside.
First, I would use Oxalic Acid on the bulkhead. Do several treatments, rinse, and let stand for at least a week. Our eyebrow went from an almost black piece of old wood to a nice blonde piece of teak that looked fresh and new and ready for varnish.

[JPA Cate]

Thanks, Iron E, love the Prime Mold Fertilizer concept!

Actually, I hand sanded my objects, and the process was quite satisfying, bringing up the natural color of the teak. It's possible the OP's bulkheads were varnished, then oiled for appearance's sake; on a similar vintage boat, ours were varnished. He may be able to just wash off the moldy part. People often use vinegar for that, but the water with clove oil should work, too. Depends on whether you want to smell like apple pie or salad!

Ann

[n5ama]

Thanks to all who offered suggestions. All good! I think my first step will be a wipe down with concrobium to rid my self of the immediate problem for the short term. This should buy me some time for a longer term solution which I will apply to some areas that are somewhat hidden.

I’m not sure what the builders of the Contessa initially used on the bulkheads but I feel that it’s original. It still looks great but the atmosphere in the Gulf of Mexico is loaded with mold and mildew and a person taking a deep breath has just inhaled enough mold and mildew spores to contaminate hundreds of boats. All it needs is a little warmth and moisture and we have a surplus of both down here.

Thanks again,
Tom

[nuku34]

Hello n5ama,
I spend many years making custom furniture using various hardwoods, oak, ash, cheery, European beech, NZ matai, etc. My preferred finish was the following: 1/3 spar varnish, 1/3 boiled linseed oil, 1/3 mineral turpentine (paint thinner). Its a compromise between straight varnish (which creates a film that stays on top of the wood, goes hard, and has to be applied with a brush) and straight boiled linseed oil (which sinks into the wood but never really hardens and can be applied with a rag). Linseed oil by itself will attract mould and get dirty. Varnish won't attract mould, but is prone to getting scratched (that's why many cruisers prefer a satin varnish which doesn't show scratches as easily as gloss).
My compromise finish sinks into the wood (with the help of being thinned by the turpentine), but the varnish component makes it go hard so you don't have the sticky oiled surface to attract dirt and mould. The mix is best applied warm with a rag. Keep applying it with about 10 minutes in between coats until the wood won't soak up the mix. Then wipe off the surface with clean rags until there's no more mix coming off onto the rag. It will dry in a day. You can re-new the finish anytime down the track by cleaning with trups and reapplying as above.

To the OP:
Note that your "teak" bulkheads are almost certainly NOT solid teak, but marine ply with a teak veneer. If you are lucky, that veneer is fairly thick (maybe 1mm), but it could be less. In any case, be very careful if you sand or scrape the veneer during prep for finishing. Its easy to sand right through thin veneers.

[GordMay]

Regardless of whether clove oil kills mould, and for how long, without damaging/darkening/staining the teak finish [or not], it is still important to address the root cause of the mould, which is moisture, caused by excessive condensation, inadequate ventilation, plumbing or structure [windows/hatches, mast step, etc] leaks, flooding, or high humidity.
For small spot removal, there are several DIY remedies using clove oil. However, these will only work as a temporary solution.
Unless the cause of the problem is solved, the mould will return.

[geoleo]

Originally Posted by n5ama

My Contessa 32 has teak bulkheads, cabinet doors etc. They are generally in great shape but since moving the boat from the state of Maine to (on the hard and wrapped during the winter) to south Texas (in the water and warmer all winter), I see some light mold/mildew forming especially on the lower surfaces

What would be a good treatment/preservative to put on the interior surfaces to address this issue? I’m really not interested in a varnish or anything that will dramatically change the color or shade. Is there an oil treatment that can be used here? I’ve read in past responses to this problem that say oil promotes mildew growth and that is counter to what I want to do.

Thanks in advance for any help,
Tom

MOLD AWAY a spray from HOME DEPOT kills existing mold quickly and nicely. Then leave a thin clean film of it on all existing surfaces and that keeps mold from returning.

[TeddyDiver]

Ethyleneglycol is pretty good against mold to grow back. Especially so on wood or any purous surfaces.

[n5ama]

Originally Posted by TeddyDiver

Ethyleneglycol is pretty good against mold to grow back. Especially so on wood or any purous surfaces.

I’m certain the teak used in my boat has a plywood base and if I did any sanding, it would be very light and with the grain of the wood.

What is Ethyleneglycol? Is it. More effective than concrobium? Does it darken the wood?

Thanks,
Tom

[GordMay]

Originally Posted by n5ama

...
What is Ethyleneglycol? Is it. More effective than concrobium? Does it darken the wood?
Thanks,
Tom

Ethylene glycol ≈ toxic anti-freeze

[TeddyDiver]

Originally Posted by n5ama

I’m certain the teak used in my boat has a plywood base and if I did any sanding, it would be very light and with the grain of the wood.

What is Ethyleneglycol? Is it. More effective than concrobium? Does it darken the wood?

Thanks,
Tom

The stuff they sell for car cooling systems (there also another stuff with another chemicals which doesn't fit for this purpose), it's a bit coloured, green here in Europe but you can get the clear stuff as well. I have a 30 l canister of it. Monoethyleneglycol, it's water soluable and a bit tacky if applied too much but you can wipe with wet cloth the excess off.

[Iron E]

Originally Posted by JPA Cate

Thanks, Iron E, love the Prime Mold Fertilizer concept!

Actually, I hand sanded my objects, and the process was quite satisfying, bringing up the natural color of the teak. It's possible the OP's bulkheads were varnished, then oiled for appearance's sake; on a similar vintage boat, ours were varnished. He may be able to just wash off the moldy part. People often use vinegar for that, but the water with clove oil should work, too. Depends on whether you want to smell like apple pie or salad!

Ann

Oh yeah, we sanded... there was plenty of that.
I'm probably talking about something different than OP. We were dealing with the exterior.
The Teak oil that the PO used made the eyebrow dark, dirty, and grungy. When we finished sanding there were obvious issues with grains and staining... Most likely Tannins.

I'm going to write down your Clove Oil water idea in case we ever have any interior issues.

[thinwater]

Originally Posted by geoleo

MOLD AWAY a spray from HOME DEPOT kills existing mold quickly and nicely. Then leave a thin clean film of it on all existing surfaces and that keeps mold from returning.

Bleach and washing soda. You can do better for much less.


https://www.practical-sailor.com/blo...at-really-work


Formula B. You can substitute washing soda for TSP if you can't find it. TSP cleans better, but washing soda works just as well for repelling mold. It's the borax that is the biostat. The others ingredients just adjust the surface pH, which is also important.