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A couple of years ago, we purchased a beautiful teak outdoor table. I sealed it with Semco sealer (recommended by the store for teak) a month after we bought it. To protect our investment, we also had a custom cover made for the table to protect it from rain and sun. Unfortunately, we got a lot of rain recently and when we took off the cover, the teak was covered with mildew spots. The water got through the cover and was trapped inside. I first tried mild bleach to remove the spots. That didn't take all of them out, so I tried a stronger commercial product. This didn't work either and just left the table looking faded and splotchy.

So I'm thinking I should just refinish the surface. I've done some reading on this, and I'm thinking I'll start with 120, then 220, then seal with Semco. Is there anything I should watch out for? How deep to these mildew spots go? Should I use an orbital or straight sander? I'm hoping I won't have to strip off too much of the wood.

Any advice appreciated! Thanks.

photo showing mildew damage

close up of mildew

after sanding

end result. much better!

Techmec
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  • Check this out first, https://woodworking.stackexchange.com/questions/3778/can-i-run-pressure-treated-deck-boards-through-thickness-planer/3787#3787 If you do end up sanding you'll probably want to start coarser than 120, significantly coarser is not a bad idea as long as you're careful and you sand up through the grits afterwards. By the way is this hand sanding or power sanding and if the latter what kind of sander (belt, ROS etc.)? Now re. the Semco, was the specific product you uses Semco Teak Sealer Natural Tone? – Graphus Apr 24 '19 at 18:13
  • Thanks, @Graphus. I do have a cheap pressure washer that I used on my fence. I had read that pressure washing can damage the wood, which is why I shied away from using it on this expensive table. What are pros/cons of pressure washing vs. sanding? As for sanding, I was planning to rent a power sander (either orbital or the straight type) from Home Depot. Yes, I used Semco Teak Sealer but in honeytone (http://semcoteakproducts.com/semco_products.htm). – Techmec Apr 24 '19 at 19:12
  • Pressure washers can damage wood, but then sanding can be thought of as a form of damage too. If you end up sanding, the 'straight type' is a belt sander and it's the right kind of sander for removing a lot of material — they are aggressive, care is needed in handling. Google for more. The orbital or random-orbit type is more a finish sander, although plenty of people these days use them for more than that! You have to be careful with these sanders too, even using finer grits, as it's still very easy to round corners or edges unintentionally. [contd] – Graphus Apr 25 '19 at 07:27
  • BTW if you haven't heard this yet it's considered good practice to hand sand (backed by a block) after power sanding, using the same final grit but sanding in the direction of the grain. This is to remove any traces of cross-grain sanding marks. Not everyone does this so it's entirely up to you, everyone decides for themselves what standard of surface they can live with. – Graphus Apr 25 '19 at 07:29
  • Thanks, @Graphus, for the great info. I'll work on this this weekend and will let you know how it goes! – Techmec Apr 25 '19 at 16:19
  • Welcome. Do be sure to let us know if the pressure washing alone does the trick! It would be great for you if it does. The legs on this are painted yes? Be careful not to get the full force of the spray on them or Bad Things may happen o_O – Graphus Apr 25 '19 at 16:33
  • @graphus: I added a photo to show the result after some sanding. (I did try pressure washing, but it didn't help.) I used a sheet sander. 100 grit didn't do much so I used 60 grit. The result in the photo is after 7 or 8 passes. It's better (most of the mildew spots are gone and some of the teak's honey color is visible again). But there are still gray/silver areas that look like what teak looks like if it's naturally weathered in the sun. Question: can I sand that gray away if I keep going? I would have to go with a coarser grit, but I am loathe to lest I take too much off or damage the wood. – Techmec Apr 30 '19 at 01:31
  • Yes you can get below the grey if you keep on sanding. The discolouration is surprisingly shallow often — a mere fraction of a mm. But sanding can be surprisingly slow, even with very coarse grits unless a belt sander is used. It would be much more efficient to plane the top (only a few passes would often be enough for me to remove the grey on well-weathered wood) but you don't have a plane so that's out. – Graphus Apr 30 '19 at 06:40
  • P.S. You may find you want to hand sand the top, along the grain, after any power sanding and if so see if you think a DuraGRIT block is something that you'd want to invest in. – Graphus Apr 30 '19 at 06:45
  • @Graphus: I was able to borrow a belt sender this weekend and sanded away the gray. Looking much better now. DuraGrit looks cool. I'll keep in mind for future projects. Thanks again! – Techmec May 06 '19 at 05:16
  • Excellent. Belt sanders make such a difference when you need to sand away a lot of wood. Harder to control but often well worth the effort. Hand planing is better way to remove this much wood all round, but it's not a viable option for someone who isn't a woodworker. – Graphus May 06 '19 at 06:56
  • That looks like new, well done. – Graphus Jul 05 '19 at 06:51
  • A little late to the party, but if you're planning on continuing to use the cover for your table (looks fantastic in the "after" pic, BTW!), I might suggest getting some "Painter's Points". Put them on the table, then put the cover over them. They should hold the cover above the table to allow for airflow so that it can dry out from any moisture that might seep through. Not sure how big the table is and how many it might take to keep the cover up. Jacks may be a cheaper option if you need a lot. – FreeMan Aug 07 '19 at 20:25
  • Thanks for the tip, @FreeMan. My thinking right now is to keep the cover off this winter. Good point about keeping the cover raised. The thing is, I realized that the cover is trapping a lot of moisture inside. The underside of the table is very moldy (which I've done nothing about), and even the legs of the chairs had mold spots that I had to clean off. So I've decided weathering from the sun is better than mold/mildew from the moisture! – Techmec Aug 09 '19 at 06:57

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A few years ago I had the chance to refinish a beautiful teak deck chair. Teak gets that grey color with age, and when you refinish it, a little of that grey actually looks beautiful.

I think you would be making a mistake to sand it heavily, if there are no major marks or gouges, try only sanding with 220, lightly and uniformly. Those little dark speck will come out mostly, and I wouldn't get too crazy about getting them all out. If you over sand one spot to get it out, you will create a bright spot in the finish that looks worse than the little black spot would have.

After that, all you want to do is rub the whole thing with teak oil - you will be astounded by the amazing depth and color of well oiled teak. If I owned this table, I would re-oil it annually, or semi annually, and I would not keep it covered.

Paul Davis
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  • Thanks, Paul. After a few passes with a belt sander using 220, I did manage to restore the table. I am happy with how it turned out. I should have posted an "after" photo. I'll attach one up top. I'm curious, do you feel teak oil is better than sealer, like Semco? I've read that sealers provide UV protection that prevent graying. – Techmec Jul 05 '19 at 03:40
  • @Techmec - I do not have any experience with Semco, so as with any new product - its good to test it on a spot that is not highly visible, like the underside of the table, to be sure you like the look. – Paul Davis Aug 19 '19 at 14:32