Black stains on varnished rubrails - help

[Jer]

http://pic20.picturetrail.com:80/VOL1427/6681690/12866561/367612591.jpghttp://pic20.picturetrail.com:80/VOL1427/6681690/12866561/367612593.jpg

Hi there. So after 2 1/2 years since completing my boat I've developed these black stains along the varnished rubrails (southern yellow pine). I realize now that I should have re-varnished several times by now, so having now brought the boat back to the garage for maintenance, I find myself not sure of the best remedy. So far I have sanded off the varnish at all these spots, and in one area sanded through the black stains down to bare wood. I was surprised and disappointed how far down I had to go! A friend suggested wood bleach (oxalic acid) as an alternative to sanding through it all, so I tried that today (3 applications) and there was no noticeable improvement. Any suggestions? Do I just have to sand through it all and if my rubrails get diminished too much glue on more wood? I assume it would be a problem to just varnish back over these spots and leave them, but am I right about that?

By the way here we are sailing in happier times:http://pic20.picturetrail.com:80/VOL1427/6681690/12866561/367613160.jpghttp://pic20.picturetrail.com:80/VOL1427/6681690/12866561/367613163.jpghttp://pic20.picturetrail.com:80/VOL1427/6681690/12866561/367613168.jpg

[Lew Barrett]

This sort of dark staining is very difficult to remove, and not made any easier if you have sanded them first. An acid wash or two will probably not remove it.

Varnish, even in copious quantities is not impermeable to water. I only wish it were! Accept it as a reminder of the immutability of time and tide.

[Cuyahoga Chuck]

I have a lot of similar stains on the bottom of my plywood canoe. They occured because the epoxy coat was breached by abrasion and microbes got into the plywood. I think it has something to do with the species of wood the ply is made of.

[Bob Smalser]

So after 2 1/2 years since completing my boat I've developed these black stains along the varnished rubrails (southern yellow pine).



It's Blue Mold on sapwood.

Wide-ringed, plantation SYP doesn't have any heartwood because in most species it doesn't begin forming until 15-20 years and the tree is harvested at 30 or 40 years.

You can strip, bleach and revarnish, but it'll happen again. Redoing them in heartwood of a durable species is the only permanent fix if you insist on varnish.

[Jer]

OK, thanks for the info. As an alternative to replacing the rubrails what would you think about stripping the varnish and coating the rails with epoxy before re-varnishing? If the SYP is going to continue to develop mold I wonder if an epoxy coating would keep moisture away and inhibit or at least delay this more than just varnish. People have also suggested Bristol finish to me in the past--any experience or insights on this?

[lagspiller]

You can use clorin bleach and sunlight.

On reddish woods we often use a rust remover with phosphoric acid actually made for iron. Ferobet. That works very well. I think they have also made a 'clear' type that can be used on white woods. Don't know if these products are available in the States, but clorin surely is.

Apply and let it dry completely before sanding and varnishing.
This kind of black stain is mostly a problem of appearance. If it gets out of hand you might paint over, but one of the good things about varnish is that you have a very good control over what is happening beneath the finish - and reason to do something about it before it does get out of hand.

[Bob Smalser]

As an alternative to replacing the rubrails what would you think about stripping the varnish and coating the rails with epoxy before re-varnishing?

If the SYP is going to continue to develop mold I wonder if an epoxy coating would keep moisture away and inhibit or at least delay this more than just varnish. People have also suggested Bristol finish to me in the past--any experience or insights on this?

Now that live mold has found itself a sugary sapwood home, from here on out for brightwork you'll have to strip, bleach and varnish them every year...and epoxy will only delay that a few months. If I were you I'd strip, bleach and paint them with a lead or copper primer beneath, replacing them when they begin to get punky in perhaps another 5 years.

Otherwise replacing them isn't a big deal. A couple each scarfs, passes through TS and planer and easing two edges. Your guards were designed to be easily replaced.