Cleaning oxidised teak below failed varnish

[superheat6k]

I have this morning stripped the failed varnish on a trim rail about 30mm think and of rounded section that passes right around the upper structure just below the flybridge level.

Where it joins the hull and in considerable patches right around the trim strip where the old varnish had failed, are dark oxidised area, so having stripped it with a heat gun I now have quite a few dark unsightly patches, with the areas abutting the GRP quite hard to get to with a palm sander.

I am going to try Wessex two pack, but are there any other chemicals I could try to get the teak refreshed right up to the joint.

I am also looking at using a small detail sander, but don't want to damage the gel coat where the teak joins the GRP. Any specific makes of sander to consider for this task ?

My palm sander simply dances when I try to sand up to the edge line, as it is only sitting on a curving surface ~ 10 mm wide before it curves away from the sander surface.

 

[Fr J Hackett]

I have this morning stripped the failed varnish on a trim rail about 30mm think and of rounded section that passes right around the upper structure just below the flybridge level.

Where it joins the hull and in considerable patches right around the trim strip where the old varnish had failed, are dark oxidised area, so having stripped it with a heat gun I now have quite a few dark unsightly patches, with the areas abutting the GRP quite hard to get to with a palm sander.

I am going to try Wessex two pack, but are there any other chemicals I could try to get the teak refreshed right up to the joint.

I am also looking at using a small detail sander, but don't want to damage the gel coat where the teak joins the GRP. Any specific makes of sander to consider for this task ?

My palm sander simply dances when I try to sand up to the edge line, as it is only sitting on a curving surface ~ 10 mm wide before it curves away from the sander surface.

Hand sand and that with oxalic acid solution wear a pair of latex gloves and don't drink it, it isn't good for you but in relative terms it's fairly innocuous if treated with a little respect and caution. There used to be a proprietary product that was essentially the same thing and sold with a secondary sealer, probably still is.

 

[Sandy]

Hand sand and that with oxalic acid solution wear a pair of latex gloves and don't drink it, it isn't good for you but in relative terms it's fairly innocuous if treated with a little respect and caution. There used to be a proprietary product that was essentially the same thing and sold with a secondary sealer, probably still is.

Then use Le Tonk rather than that two pack stuff.

 

[Buck Turgidson]

I used a cabinet scraper rather than just sandpaper when I had the same issue. I found it much quicker but care is required.

 

[superheat6k]

Thanks. I already have the Le Tonk ready.

 

[Tranona]

Did that job last year. Heat , Bahco scrape and sand. Bleach for light staining. Very little that needed more and left it as overall appearance was fine. Oxalid acid will lift dep stains eventually - most of the proprietary cleaners like Wessex are oxalid acid based. 5 coats of International Woodskin. Example of end result

 

[Mistroma]

Yet another reminder that the rate of reaction with oxalic drops dramatically at lower temperatures (pretty much my automatic response every time a post discusses oxalic). Fine on a sunny summer day where it will have an almost immediate effect at 25-30C. It can take hours to have the same effect on a cold day. I think a pronounced reduction in speed take place below 10C.

I always pre-heat fibreglass with hot water and dissolve oxalic in hot water if working on a hull in winter. Not quite so easy with a teak deck as the hot water will heat the wood but also reduce the uptake of the oxalic solution. Try to work on wood that's been warmed by some sunshine, dissolve oxalic in hot water and add a couple of drops of washing up liquid to reduce surface tension, helping penetration.

 

[Fr J Hackett]

Yet another reminder that the rate of reaction with oxalic drops dramatically at lower temperatures (pretty much my automatic response every time a post discusses oxalic). Fine on a sunny summer day where it will have an almost immediate effect at 25-30C. It can take hours to have the same effect on a cold day. I think a pronounced reduction in speed take place below 10C.

I always pre-heat fibreglass with hot water and dissolve oxalic in hot water if working on a hull in winter. Not quite so easy with a teak deck as the hot water will heat the wood but also reduce the uptake of the oxalic solution. Try to work on wood that's been warmed by some sunshine, dissolve oxalic in hot water and add a couple of drops of washing up liquid to reduce surface tension, helping penetration.

Basic physical chemistry simply use a saturated warm solution and you will find it works in normal spring temperatures you really don't want to be doing it in freezing temperatures.

 

[Mistroma]

Basic physical chemistry simply use a saturated warm solution and you will find it works in normal spring temperatures you really don't want to be doing it in freezing temperatures.

Yes, that's why I mentioned temperature. It helps a lot to warm the GRP, teak etc. as that slows cooling of the solution as it is applied. I did see a rate of reaction graph for oxalic acid many years ago and seem to remember it curves down rapidly with a pronounced dip around 10C where it really slows. It would be about 40 years ago so detail a bit fuzzy.

I've come across a few people who said oxalic was useless and invariably found they'd been using it in a yard over winter.