Sanding teak

pugwash

pugwash

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Just inside my hatch I have a wooden flap about 18 by 28 inches that hinges over the engine and does double-duty as top step and galley work-surface. Shiny varnish finish. Last week we managed to bubble the varnish with a hot pan so I brought the flap home to sand and re-varnish with polyurethane. I got the varnish off easily but realised only when I'd finished that there were some faint scorch marks from the heat gun, like greyish blushes, on the surface. With my B&D orbital sander I went through ten sheets of coarse sandpaper in about 90 minutes and it hasn't made any difference at all. If anything, iut's getting worse. I think -- not entirely sure -- that the wood is solid teak. Is teak made of titanium or something? I thought it would be a piece of cake to sand off the top layer; no way. As I have a lot more varnish to re-do in other parts of the boat I'm pretty concerned. Lesson one: don't scorch the wood. But now that I've got the problem, and learned a lot, what can I do about it? Just keep sanding or is there a short-cut?

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if it's solid teak, you could try a fairly strong sloution of oxalic acid on the wood, but I do hope it's not teak faced ply, because you may well have sanded through the top veneer layer, the glue looks grey when you sand through it. Teak is not normally difficult to sand, it's a fairly soft hardwood?? Which sands easily, normally. 18 x 28 is a big piece of teak, how thick is it? Does it have edging around it? If it has then, I suspect it's ply, that size. If it's ply, it's too late. You will have to replace it. not as expensive as you may think. But you will have to re-edge it, have a very close look at it. You can also bond on top of the panel with very thin (4mm) teak faced ply, but for a piece this size I wouldn't bother. Let me know what you find.

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Not carconegenic, but you will get sensitised to it. Just like a certain Scott around here, that can't sand anymore without a mask a hood and gloves!!

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Scotty -- I don't think it's ply. The flap is actually three different 10-inch boards or planks with an all-round edging, 5/8ths thick. I have made a tiny hole in one spot to investigate what's underneath, and if it's ply I'm nowhere near the glue. I don't want to dig down too much. There's a lot of solid teak in the boat, most of it beautifully finsihed, so i have to learn how to get it right before proceeding with further stripping and revarnishing. While burning off I thought I was using a delicate touch with the heat-gun and never saw the wood burning or darkening. It was only afterwards, after I did the first sanding and stood back, that I saw the grey bloom. When the surface is made wet, suggesting the final finish I'm likely to get, the grey colour stands out horribly. I'll try the oxalic idea later today. Thanks for your input. Hope the sun is shining where you are.

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Yes, you develope a sensitivity to the dust and it attacks your breathing, skin and gives you all kinfs of symptoms, like hay fever, i suffer really badly, a pity whjen my whole boat is teak! or Iroko, which does the same, mind you the iroko is painted, looks like shit varnished.

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Re: looks like shit varnished

Ooooops! Did I say that! Too late to edit it aswell!

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Try a cabinet scraper

try a cabinet makers scraper, basically a flat piece of metal say, 75 x 100 mm with a burred edge, achieved by pulling the round steel part of a screwdriver over it several times. Use at a right angle to the wood, two handed, with your thumbs behind and fingers in front and scrape away! Works for me!

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Another question

The oxalic didn't make any difference at all but I had another thought. The grey areas are getting bigger and after a sanding session I suddenly realised the area was very hot. Do you think I could be cooking the wood by friction? Is it possible to sand too hard? So far, I've got nothing but a right old mess despite many sheets of sandpaper. Maybe I should take to a scraper.

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ok, first off, get the orbital sander and throw it away. These appaling devices have no place when working with wood. They cut across the grain, so will scuff it horribly, and are uncontrollable if trying to remove any material. Like wise the vibrating things, useless if if you want a first rate finish.

Second, is it real wood or not? You don't say how thick it it. It is not common to find teak 18 inches width. But on your older boat, quite possible. At the ends, if the grain is not an end grain, but looks the same as the face, it is teak-faced ply. On the faces, for real wood, there should be a constant grain pattern. You can read the wood a bit better sometimes by wiping with a damp cloth. If the wood is becoming darker, with a cross grain where you have sanded - it is ply. If unsure, get a woodish type of person to have a look. After 10 sanding sheets i reckon it might be solid.

To remove wood and flatten the surface, as another poster says, use a scraper - a flat piece of steel drawn back againt the wood with both hands, and with the grain. This gives a fairtly smooth finish and removes surprising quantities of wood - so be careful. For smal area a "stanley knife" blade works well. There are purpose-made devices (not at B+Q mind) for scraping.

Sanding the wood is a patient process. Again, do not let that orbital sander anywhere near it. On a relatively flat scraped surface, start with no harsher than 180 grade preferebaly finer, and always alway always sand in the direction of the grain. Use a block to prtect your knuckles. You will need the wood held in a jig, but use soft jaws or soft blocks to protect it in a vice.

"Lift" the grain by wiping with a damp cloth - this will bend any wood fibres that will otherwise only bend when you varnish - which is why most amateur applied varnish is blimmin awful and rough. Allow the wood to dry, then sand it down. Do this again and again and again and again, with progressively finer and finer sandpaper. Eventually, a damp rag will have no effect. It is quite possible to have the wood so smooth and shiny that you cannot tell if it is polished or not, and certainly a whole load smoother than a baby's bum. Use very big numbered grades of paper, or flour paper, and as the wood gets smoother, "warm" the sandpaper by rubbing it against another sheet before use.

For varnishing, you first lay the dust all around with a water spray. Pour a bit of varnich into a container and close the tin, ensuring nio gunk gets in the varnish. Soak the brush beforehand for a good while in water and use real bristles, not the crappy plastic ones. Don't use a brnad new brush on important pieces - break them in by harshly "painting" another piece of wood with water, to knock out the loose bristles, and clean again. Apply a very very thin fast coat that barely covers, and allow to dry. Spend more time on the end grain, which absorbs the varnish. Do it at all some speed - you should hardly ever catch a decent painter doing any painting - most of the time is sanding down. In warm weather do it before midday. Wait 24 hours at least and sand with flour paper after each coat - and by now the paper should be so fine that you would be fine about sanding your skin with it, and warmed as above. Expect to apply more than eight coats before a deep shine appears. Don't be tempted to use heavy coats or you will get the nasty gloopy (yet often very shiny) look with too-rounded edges.

The above is for raw wood. You should not need to return already-varnsihed wood to raw wood state - but with a varnsih you would expect to appy a coat of varnish or two every season for "dress" areas - but the proces is quick - tape off the area, sand down one day and varnish the next. You need only knock down the shine of the existing varnish, not remove it completely for the shine to build and build.

Because of the massive time and effort needed for all the above, you may be tempted to consider buying a boat with not one bit of varnished teak anywhere at all. I did!

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Phew! Thanks for this. Highly educational and my heart is sinking. I don't doubt that you're right but it's not a perfect world and if I did all this I'd be dead before I hoisted sail. The need is to find a practicable compromise - aspire to be perfect but end up with something looking pretty good. Museum-quality finish is not as important as a finish that lets me go sailing in a pretty boat.

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Thanks for this hi-tech bit of advice. I have filed it away for future reference.

Incidentally Lynn Pardey did an interesting article on varnishing many years ago in PBO. It started out by her spilling a tin of varnish in the bilges and so she decided to varnish all of the bilges.

John

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Re: Try a cabinet scraper

Or a piece of broken glass. I had a similar problem on a badly weathered cockpit table and was about to persuade my wife that I needed a cabinet scraper when she came up with the broken glass idea that she had "read somewhere". Conveniently the kids next door had put a football through the greenhouse the previous week so I had plenty of broken glass to hand. Talking of hands however I did end up in casualty for stitches when the piece I was using broke so use strong leather gradening gloves.

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Re: looks like shit varnished

They varnish caribou dung in Alaska to make into 'amusing' sculptures & sell them to Cheekako's (tourists up for the summer). [Bet you didn't know that!]

Iroko dust is certainly carcenogenic, as classified by the HSE.

Regards

Richard.


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Re: well then....

a woodworking/joinery shop will have decent quality tools to effect the job remarkably cheaply. Make sure you tellem it is part of a kitchen, not a boat.

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moose is different

But I do have a varnished moose turd on a magnet on my fridge. Bet you didn't expect that! Bought for one dollar at the annual Moose-dropping Festival in Talkeetna, Alaska. They collect thousands of pellets and give them numbers. You buy one then all are dropped from a great height and the one nearest the centre of the target wins the pot. Such is sport in the Frozen North. Come to think of it, the finish is pretty good.

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