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Author Topic:   Inky Streaks
waterwal posted 02-28-2003 11:12 AM ET (US)   Profile for waterwal   Send Email to waterwal  
I bought what was a 17 bare hull which the previous owners had converted to a center console with bench and helmsman-style chair seating. The benches were rotting and beyond revival, so I had a local carpenter fabricate replecements for me. Ultimately I plan on installing an OEM RPS, so I wasn't too picky about the wood type. I went with red oak as a cheaper, but worthy replacement for the old Mahogany.

The finish is beautiful, but my question relates to a stain that appeared where the screws fasten the bench to the console.

Within a couple of weeks of installing the bench, a dark streak began to appear near the screws. Over a few months it spread in longer and narrower streaks extending about a foot from the screw holes. I originally thought that water was getting in there and somehow staining or rotting the wood, but wasn't sure because it happened so fast.

A guy at my local marine supply told me that he used to be a carpenter, and he knew that stainless when in contact with certain kinds of wood, like oak in this instance, induces a chemical reaction in the wood which results in that inky streak. I'm not really concerned about the wood, and I could even say that it has a nice weathered look to it. Still, I'd rather know what's going on, if for no other reason than mere curiosity. Any ideas? Is this guy right? thanks in advance.

Montauk posted 02-28-2003 10:25 PM ET (US)     Profile for Montauk  Send Email to Montauk     
Are the screws plugged? Are the screws stainless? Can you call the carpenter and find out what he used? I have a feeling if he used Red Oak the screws are not silicone bronze as they should be. If stainless is deprived of oxygen there is a chemical reaction that causes it to weaken and eventually disintegrate. I believe red oak is acidic and steel screws would make it stain dark if humid.
Whaler Proud posted 03-01-2003 12:59 AM ET (US)     Profile for Whaler Proud  Send Email to Whaler Proud     
I agree with Montauk in his assessment about the screws, but I have found that oak is notorious for developing these stains when left outdoors in a damp environment. Most I have seen originate around holes whether plugged or not. In some cases certain parts of the grain have turned the "inky black" you describe giving the wood a "fungal" appearance.

I have had success bleaching the stains out and then refinishing. I have yet to figure out (or taken the time to learn) of a way to prevent this. Maybe Tom Clark can weigh in since woodworking is an area of expertise for him.

waterwal posted 03-01-2003 08:15 AM ET (US)     Profile for waterwal  Send Email to waterwal     
The screws are sealed. They're also stainless, marine grade which I bought (the carpenter just cut the wood for me, and I did the rest). I guess this explains the reason why oak is almost never used for marine applications. What is notable is that since the end of the season last year, the stain hasn't spread, which makes me suspect the chemical explanation. Whaler Proud's observation regarding humidity could be the answer despite the seal.

Preventatively, it sounds like there isn't much I could do. As for bleaching, I might be willing, depending on how involved the process. I do not want to have to strip the wood back down, since the RPS should be ready to install by fall...anyway thanks for the help. I appreciate it!

Whaler Proud posted 03-01-2003 11:17 AM ET (US)     Profile for Whaler Proud  Send Email to Whaler Proud     
I always remove the finish and then paint on basic chlorine bleach. Let it dry out a couple of days before applying the new finish.

This seems to delay the streaks for quite some time but they inevitably return.

OutrageMan posted 03-03-2003 03:07 PM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
This topic has been discussed here:

http://www.spaltedboard.com/cgi-bin/index.cgi?action=forum&board=Finishing&op=display&num=247

waterwal posted 03-03-2003 07:07 PM ET (US)     Profile for waterwal  Send Email to waterwal     
OutrageMan- Thanks for posting that question. It sounds like this reply explains it best: "My guess is that it is a result of two things. First Oak has a high tannin content, and that may be leaching material from the screws - especially if just black drywall type screws were used. Also, Oak is one of the most porus wood out there. That also gives a path for that material to streak."

Interesting in that it's French and American oak that's most frequently used (stainless steel coming 2nd, ironically) for wine casks, due to their tannin content improving the wine.

That said, most of those folks seem to think that stainless screws would not cause this, and my screws are stainless. Odd.

By the way, I like your quote about the smell of fresh cut wood. I'm no carpenter, but I agree. In retirement I dream of being a carpenter. (:

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