Black Stains on Mahogany

[John R Smith]

Folks

this week's job is to renovate Lulu's forehatch. We have unscrewed all the hinges and have it at home on the workbench.

I have stripped all the old varnish and sanded everything smooth, but even so there are still lots of unsightly black stains or streaks in the wood. Is there any way of dealing with this, other than sanding off loads more wood and reducing the thickness of the board?

John

[pcford]

Oxalic acid. Mix strong solution of crystals and hot water. Repeat until stain is gone. Wear good mask when sanding.

[Concordia..41]

Ditto on the oxilic acid. Particularly bad spots may take a second or third treatment. Use a Q-tip or small brush to retreat the spots until you're satisfied. Rinse throughly and allow to dry overnight after each round. That way you'll get a good feel for the color and you'll probably see a few crystals expelled from the wood grain - showing you didn't rinse quite as completely as you thought.

http://www.sailingwithsarah.com/Pic/Tiller4.jpg

http://www.sailingwithsarah.com/Pic/Tiller3.jpg

More pictures at: http://www.sailingwithsarah.com/refinishingtiller.htm

Hello to Lulu and Kate smile.gif

- M

[John R Smith]

Thank you folks for your help. Looks like a trip to the chemist at lunchtime ;)

And hello to you, Margo, from a very wet and gloomy Cornwall this Wednesday.

John

[Bayboat]

Hi John. The oxalic works best in bright sunlight. In view of your latest weather report, I suggest you take your brightwork to southern Spain for treatment.

[John R Smith]

Sunlight?

No-one mentioned sunlight. Is that why it doesn't seem to do much? And I was working in about 40 deg F - is it temperature sensitive too?

Unlikely to have much sunlight for a month or too . . .

John

[Concordia..41]

Yes John - I don't know if it's temperature, sunlight, or both. Hot water definately gets superior results. In my origininal post I was going to suggest letting the piece dry in the sun, but it seemed a cruel instruction given your climate. :(

As a side note, I started that tiller at least three months ago and, no surprise here, I'm still varnishing, but some of those dark spots are definately starting to come back. It's subtle, and I wondered if it was just my imagination at first, but looking at these pictures makes it very clear.

Lesson learned is not to worry about getting the spots a little too light.

Also, there was a far greater and more dramatic impact on this locust than I've had on mahogany. I easily had five rounds of bleaching, drying, sanding, staining on Sarah's mahogany transom before I was satisfied.

As Rocky said the other day, "Wooden boats are God's way of making us appreciate repetitive tasks."

Cheers!

- M

[John R Smith]

Thank you Margo. I think you have got a great deal more patience than I have.

How are you ever going to dare to USE that boat? I mean, the finish on your stuff must be beyond unreal - but there will be blocks, and flailing sheets, and feet, and sun and rain, and anchor chains. How will you bear it? ;)

Finished varnishing the cockpit locker lids four weeks ago. Put them back in the boat, got the toolbox out, forgot, dumped the toolbox on the locker as I usually do - great big scar on my new varnish. Ho hum, workboat finish is my new mantra . . .

John

[Concordia..41]

No worries John - it'll never be finished at this rate ;)