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Madu
08-16-2008, 07:30 AM
Hello All,

I have been sanding the mahagony transom on my restoration and have noted the wood has a grayish tinge in places..from exposure to the elements I presume and neglect. I have sanded it but it has not all come out. Any suggestions on how to get to a more original shade without oversanding? Will varnish take out the gray?

Thanks everyone.

Dale R. Hamilton
08-16-2008, 05:34 PM
Madu- You can bleach out the entire transom to almost white. Do this with a wood bleach containing __________, mmmm can't think of the compounds name. Forum?? Once you have it a uniform white or light gray color, stain it back to whatever you want and it should take an even color.

Peter Malcolm Jardine
08-16-2008, 07:37 PM
It's Oxalic acid. It is used most commonly in premixed deck washes.. for pressure treated decks to get slime and discolouration off. Look on the bottle, it will state the ingredient. Also very common in commercial fibreglass bottom cleaners. It used to be available at the drug store in crystal form, but not up here anymore.

Apply the deck wash with a brush, let it work for a few minutes. After it is bleached, rinse it well, then wait for the wood to dry, since the grain will be raised from the moisture. Sand, then stain the wood for an even look...

pcford
08-16-2008, 09:30 PM
Madu- You can bleach out the entire transom to almost white. Do this with a wood bleach containing __________, mmmm can't think of the compounds name. Forum?? Once you have it a uniform white or light gray color, stain it back to whatever you want and it should take an even color.

You are referring to 2 part bleaches. The active ingridients are sodium hydroxide and strong hydrogen peroxide.

Use of two part bleaches should be an absolute last resort. They fuzz up the surface of the wood, making it very difficult to apply stain and varnish evenly!

Bill Lowe
08-17-2008, 05:16 AM
PC
We just used 2 part bleach on the Elco that we did and had no fuzz up I have hade that problem before but not this time and I dont know why. The boats back in the water after a little caulking and a morning soak. PS nasty stuff if you get it on your skin!

Bill Lowe
08-17-2008, 05:44 AM
Elco photo, trying to get the photo thing together. http://i539.photobucket.com/albums/ff355/wildbillboats/IMG_0675.jpg

SchoonerRat
08-17-2008, 07:52 AM
You are referring to 2 part bleaches. The active ingridients are sodium hydroxide and strong hydrogen peroxide.

Use of two part bleaches should be an absolute last resort. They fuzz up the surface of the wood, making it very difficult to apply stain and varnish evenly!

I haven't seen 2 part wood bleaches on the market for years. I thought they were banned by the EPA.

C. Ross
08-17-2008, 08:00 AM
Bill, your Elco looks really nice in that picture. Glad two-parts worked well for you this time, but I'd with pcford.

Madu is describing a very modest problem - iron in the water in the form of ferrous sulfate reacts with the tannic acid in the mahogany and creates iron tannate, which is blackish-gray. Oxalic acid breaks the chemical bond in iron tannate into its constituent elements, which are colorless and can be rinsed away.

The two-part bleaches actually destroy part of the cell structure in the wood, which removes the color entirely. It's totally appropriate to use if the wood is discolored for other reasons. It's also used by furniture makers when they want wood to be pickled, or to make the wood completely uniform for re-staining. But overkill as a first treatment for the problem as described.

So in the case I'd say: strip the finish completely, bleach, rinse, wipe with a rag in mineral spirits to see if the spots are gone, bleach again as needed, sand with 150, stain, varnish, sanding between all processes as appropriate. It'll be beautiful.

PaulC
08-17-2008, 06:43 PM
http://i539.photobucket.com/albums/ff355/wildbillboats/IMG_0675.jpg

snow(Alan H)
08-17-2008, 08:56 PM
Nice launch - do you have any other photos ? its not dissimilar to my own - more unpainted wood , but I like that - I might have to get the stripper out. Cheers Alan :)

Bill Lowe
08-18-2008, 03:56 AM
I have more pictures at the boatyard will put them up later today.

Rational Root
08-18-2008, 06:12 AM
I seem to remember that Oxalic acidis used by dairy farmers to clean the milking equipment. (I could be way wrong)

But that could be an easier source, and reasonable prices.

C. Ross
08-18-2008, 06:40 AM
You can buy a 12 oz tub of oxalic for about $6-$7 at most hardware stores. Usually labeled as wood bleach. One tub should be enough for most transoms.

Bill Lowe
08-18-2008, 09:23 PM
Photo http://i539.photobucket.com/albums/ff355/wildbillboats/image2.jpg of the Elco after bleaching.

pcford
08-18-2008, 10:48 PM
Photo http://i539.photobucket.com/albums/ff355/wildbillboats/image2.jpg of the Elco after bleaching.

Hey Bill,

How is the summer going? At your marina in NC, I remember waking up at 7am at your covered with only a sweat soaked sheet...mind you...not soaked through any activities of my own. Hope you are escaping the misery of a SE summer as best as you can.

I have bleached out a boat so that it is as white as a piece of paper. The Philippine that Chrises are made of does not like it much. I assume the Elco is made of different stuff.

When you gotta use two part bleach you gotta.

In order to match planking on a boat...typically a light new plank surrounded by older, darker wood these days I mask off the light plank with 3m chemically resistant tape and stain it with water based mahogany dye. The darkens up the plank and then I apply normal wiping stain over all.

Bill Lowe
08-19-2008, 02:39 AM
I think this photo is after scotch brite. I will send more photos. As for the heat! not to bad the last week but it was pretty rough before that. The wood looks more like Honduras Mahogany much more grain pattern than Phillippine.

Rich VanValkenburg
08-19-2008, 07:02 AM
One thing about wood bleach, no matter what it is, oxalic acid or two-part Blanchit- if the mahogany has started to break down from funugus it won't hold varnish after a year or two. I've had that happen and am seeing spots on my boat now that were in doubt. You mentioned that the wood was sligtly gray and sanding won't bring it all out. Try a super sharp cabinet scraper on those spots just to really see what's underneath.

snow(Alan H)
08-20-2008, 04:09 AM
Hi Madu
There was an excellent article on 'Using Wood Bleach' in the Dec 2002 issue of 'Wooden Boat ' magazine. If you post your email address, I will scan the 5 pages & email them to you.
Cheers Alan

Madu
08-20-2008, 07:31 AM
Hello Alan,

Email is mdjh2@hotmail.com. Thanks very much. I have tried the oxalic acid in a deck wash(thanks C. Ross) and seemed to have had some good results, but with 2 or 3 applications. But there is plenty more bright work to do, so the article will be welcome.

Cheers,

Matt(madu)

Jay Greer
08-20-2008, 10:12 AM
Oxollic acid will, in most cases, remove stains caused by corrosion of ferris metals, and mold. In extreme cases where a total removal of color is called for, a two part bleach can be used. However, one stands the chance of ending up with a less than optimum looking wood surface as, two part bleach will remove the chatocy of the grain; forever giving it a dead and listless look.
Jay