I've bought an oak table to give it a second life as our dining table, our plan is to refinish it with (hardwax) oil.

It was quite stained and originally treated with some kind of oil. So my stripping process up until now has been:

  1. Soda-water to extract the oil from the wood took out some nasty stains along the way. (this was repeated twice)
  2. Oxalic acid (on the whole table) to remove a few black rings that I guessed were caused by some metalic pots.

Now I have a few stains left that I have no real idea on how to handle them.

Here is the current state of the table top for reference: Table overview

And the following two kinds of stains that I would appreciate some advice for:

  1. Some kind of glass shaped stain, maybe wine?

glass shaped stain

  1. Some kind of oil stain of where I think the protective finish was missing and something leaked through? These are in quite some places in the table and give it a bit of a dirty look.

greasy stain

What I can find online is primarily for fixing these kinds of stains after they have just happened or when there is still some kind of finish on the wood. So what should be a sensible plan of attack here?

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    Hallo Davy, welcome to the Woodworking SE. Need to ask a few questions for clarifications. Could you tell us exactly what you mean by "soda-water"? I'm presuming it's one of a few possible strong alkalines, if so did you neutralise or thoroughly rinse the surface afterwards? And have you done any sanding or scraping yet? It looks like there's a routed detail which may present a problem with sanding much from the surface, but fairly heavy sanding may be a part of what you need to do to get the table as clean as possible. [contd] – Graphus Aug 26 '19 at 21:44
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    I'll be repeating this in my formal Answer but there's a chance you'll have to try some things and see how they work out rather than there being one clear course of action. Even when the cause of stains is known the common fix may not prove effective (for unknown reasons) and something else must be tried; and this may not work either. Because of this you could find that you won't be able to get the top 100% clean, so you may need to resign yourself to some trace of the staining remaining. – Graphus Aug 26 '19 at 21:48
  • Hi Graphus, soda-water was just, washing(or crystal) soda mixed with water. Roughly 2 tablespoons per liter of water. I indeed neutralized it with a water,vinegar,dish soap solution. There is indeed a routed detail (roughly 1/1.5mm deep) so indeed I'm trying to avoid too rough sanding. I'm happy to try some stuff, but finding it a bit hard what should be safe to try. – Davy Landman Aug 27 '19 at 5:33
  • By "Hardwax (oil)", do you mean something like osmouk.com/sitechapter.cfm?chapter=82&page=247 ? (Sold here as "Hartwachs Öl" – Martin Bonner supports Monica Aug 27 '19 at 12:58
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    The formulae for baking, washing, and caustic soda are respectively NaHCO₃, Na₂CO₃, and NaOH (which are a reliable way of confirming translations). – Martin Bonner supports Monica Aug 28 '19 at 10:42

To start I want to repeat something I said in the Comments above. It's entirely possible that no matter what you try (short of planing the entire top down significantly or running it through a wide-belt sander!) that some trace of the stains may remain and it is wise to prepare yourself for this eventuality. Reclaimed wood and previously used furniture always comes with this chance.

It's a shame about the shallow recessed detail on this tabletop because it will limit how much wood you can remove. Despite this the first thing I think you should do is some sanding.

Sanding will remove a shallow layer from the surface, taking some staining along with it as well as helping in other ways. Even though it sounds very coarse start with P60 or P80 grit and work your way through the grits to P240 at least. You may want to go to P320 or P400 because you're planning on using a hardwax oil as your finish (not something I would recommend for a dining table by the way1). Be diligent about removing all the sanding scratches from the previous grit before moving on to the next grit!

You may be pleasantly surprised at how much this step helps, but it's best to expect that it won't completely remove the stains and they're require further treatment.

Stain treatments

The rings I think will present the greatest difficulty, in part because they're fairly pronounced but also because their shape makes them stand out so clearly. If they are from red wine then scrubbing with a proprietary surface cleaner that contains chlorine bleach may be effective, if none are available where you are you may have to resort to scrubbing with a bleach solution using the rough side of a (new) household cleaning sponge. Unfortunately either may leave a small lighter spot on the wood, in which case you should treat the entire surface to even out the colour.

The stains you suspect are from oil, you could try an old trick first and that is to run a hot iron over them with brown paper in between the iron and the wood. This can sometimes liquefy the oil enough to leave obvious oil stains on the paper (which show up much more clearly on brown paper than on white paper) and will clearly identify them as oil or grease stains. Unfortunately old oil may not respond to this much as it has had a long time to oxidise and become a semi-solid, but sanding off the surface as a first step will have revealed oil deeper in the wood that may not be as fully oxidised.

If you want to proceed as though they were oil stains here is probably the best advice on how to deal with them on the Finishing Store's site, TIP: Removing Oil and Grease Stains. To briefly summarise, you treat the surface with pastes of acetone and fuller's earth2.

Finishing guru Bob Flexner warns elsewhere that with old stains it may not be possible to completely eradicate the mark, but yours aren't particularly dark (bad ones can be the colour of chocolate on oak) so I think you may get good results.

1 These vary greatly from product to product, and makers are not upfront about the ingredients, leaving us in the dark about what they actually contain (always a warning sign) and making it very difficult for consumers to do meaningful comparisons. And at least some manufacturer's claims about their durability are not to be trusted — genuine real-world testing by third parties has shown some of the market leaders to be very much less protective than advertised. So it's possible it won't be sufficiently hard wearing, heat, water and stain resistant, and will be relatively easily damaged by common household cleaners. So in short, unsuited to a dining table in regular use, particular in a household with kids.

2 Talc or other light powders (including starch) can be substituted if fuller's earth is not easy to find locally, although they may not be quite as absorbent.

  • Personally, I would stop after the initial P60/P80 sanding, and deal with the stains at that point. (The fine sanding won't remove much more depth of wood, and it will be better to do it after any treatment to ensure the surface finish is consistent.) – Martin Bonner supports Monica Aug 28 '19 at 10:45
  • Thanks for the long answer + extra advise, I'll reconsider the finish options. We are looking for a way to keep the light color of oak, and we came across some light hardwax versions, that indeed claimed great durability. But with young kids we'll have to see about that indeed. A varnish would be the classical approach, but we are looking for something less glossy. Anyway, that's a different topic. – Davy Landman Aug 28 '19 at 20:20
  • And Martin, I might do that, get the top layer of it, and then continue. – Davy Landman Aug 28 '19 at 20:21
  • Varnish can always be bought in a matt(er) version. But glossier varnishes (any gloss finish in fact) can easily be matted down after drying, to any degree desired, which is actually the preferred option for some pros instead of relying on reduced-gloss varnishes as this was the traditional approach when using shellac. – Graphus Aug 29 '19 at 7:03
  • @MartinBonner, I see your logic but I don't think that would be advisable because with P60 in particular the surface will be rough enough that it will be harder to see exactly what's going on. By preference I'd sand to P150 at least before continuing. – Graphus Aug 29 '19 at 7:08

I would try treating the rings with a proprietary ring remover, then lightly sand the surface, and apply a coat of oil. I think the oil stains will disappear.

You can get an idea of how the surface will look after finishing by wiping white spirit over it.

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