Mold, Mildew stains in oak and fir

[Iverskid]

I live in the NW and have a wooden drift boat that has mold/mildew stains in the oak rub rails and the vert grain fir thwarts and ribs. They have been teak oiled in the past and the conventioal stain removers (30 seconds, Behr) don't work. Any suggestions on bleaching out the stains?

[Landlubber]

Swimming pool chlorine, but make sure you soak it out again when finished.

[peter radclyffe]

Originally Posted by Iverskid

I live in the NW and have a wooden drift boat that has mold/mildew stains in the oak rub rails and the vert grain fir thwarts and ribs. They have been teak oiled in the past and the conventioal stain removers (30 seconds, Behr) don't work. Any suggestions on bleaching out the stains?

oxalic acid is used for some stains, ive never used it, if you ues it , i advise you to test a piece off the boat first

[aaroni]

Mold & Mildew is a non-bacterial, multi-enzymatic product specifically formulated for the cleaning, removal, and prevention of mold & mildew stain and related odor. Applications: Bathrooms, Bath Houses, Boats, Basements, Kitchens, Ducts, Vents, Walls, Floors, Ceilings, Patios, Decks, Sidewalks, Driveways, Rail Cars, Tanker Trucks, Silos, Manufacturing Facilities, Processing Equipment, and any surface where mold & mildew exists that is not harmed.

Source :
Value Dry Expert

[lonestarcruiser]

I use tomato juice on most woods I work with. Cypress (tidewater) pine, oak and beautiful poplar(for interior finish wood)
Just try a small spot and see what happens. Leave it on for several hours. Then wipe clean.
I dont know how large your area is but also to immediately eliminate the cause you can put your boat in an enclosed area and turn on a ozone generator ( available online for an average price of about $150.00) for two or three days and zap the gremlins.
Is also good for completely eliminating spores, bacteria, and viruses from your home. Especially useful during this pandemic flu thing. Read the directions. It produces the same effect as a corona discharge, ie: Lightning which also cleanses the atmosphere.
If you dont have an enclosed area you can use your boat cover.
Cheers!
Sam

[PAR]

Oxalic acid or bleach will lighten the color of the wood. In fact, I use oxalic acid for this reason when attempting to match things in restoration.

Try a diluted beach, say 50/50 which will likely not change the color of the wood too much. Oil finished pieces are prone to staining as they don't seal the wood. Also these types of finishes also can be a lovely environment for several different types of fungus and other beasties that live on, in or just under the oil.

[Easy Rider]

Our varnished or oiled teak here in SE Alaska suffers from blackish stains very soon. Some of the locals here say it's the Tung oil. Were now using Dalys teak oil an excellent product I think but wer'e still getting some stain (or at least what appears to be stain. Next spring we plan on using mildicide paint additive with more teak oil after considerable sanding. I'm beginning to think teak shouldn't ever be used on a boat. I have some red cedar varnished w Mckloski's high gloss and it has held up fine for 4 or 5 yrs.

Easy rider

[PAR]

Tung oil will darken wood, but pretty slowly. What does darken wood dramatically is linseed oil. I would never use an oil finish on anything that doesn't require it. Teak decks look great, so long as it's on someone else's boat.

[gonzo]

Oak and other hardwoods get dark stains that are not mildew. They can be bleached out, but it is really hard on the fibers.

[PAR]

Use a pesticide on the wood and mix some in with the oil as you apply it (after it's clean). I'm pretty sure it's a beastie or fungus, that can be killed or persuaded not to make a home.

[hoytedow]

Sodium pentachlorophenol is an effective wood preservative but it is very toxic and may be hard to come by. Lots of hazards are associated with it.

[Landlubber]

"Teak decks look great, so long as it's on someone else's boat."

Yep, soooooo true, sort of like a Ferrari, or Lambourghini...nice to look at, as long as someone else has to pay for it.

We are lucky in a way mate, we get to see all these beautiful toys and get to pl;ay with them, but , as you say, as long as it is someone elses....

[Submarine Tom]

Spalting is a highly saught after effect in some woods like maple.

It is the result of mold or bacteria, I'm not sure which. Are you sure you

don't want to learn to love what you've got Iverskid?

-Tom

[alan white]

I've cleaned up fir spars with black stains using oxalic acid. It comes in granules you mix with water. It can take some time for the black to go away. I let it sit for a while and then use a scrubbie (3m pad), rinse, and see the results. Repeat until the dark areas disappear, then dry and sand until you get a reasonable uniform grain color. Sometimes a filler stain helps to even out the wood's color. The darker you stain it the less contrast next time.

[CDK]

Mildew stains can be oxidized with potassium permanganate ( a purple dye). The spots turn brown and stay brown after rinsing with plenty of water. A little water in which a couple of vitamin C tablets are dissolved instantly removes the brown stains. Works on wood but -much more important- on fabrics, upholstery and sails.

For Iverskid it will be too late, he posted the question over a month ago....