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Arts & crafts

black mark on oak

(25 Posts)
Elegran Mon 15-Sep-14 10:56:23

I have sanded the top of an oak parquet coffee table, and got rid of the crazing treacle brown varnish that covered it. Turns out the oak is a lovely golden shade BUT a nasty black mark is now visible. No idea what is is/was, but apparently metal + water could have had that effect because of the tannin in the oak. I shall go and get a photo.

To get rid of the stain, Googling brings up suggestions of boric acid (I think that is poisonous and unobtainable, but could be wrong) or toothpaste - Pepsodent was mentioned, but presumable other makes are equally good.

Does anyone have any advice?

Nanabelle Tue 16-Sep-14 00:08:41

……….you'll wonder where the yellow went, when you brush your teeth with pepsodent …………..maybe it gets rid of black too grin. I didn't know it was still around.
My son has oak worktops in the kitchen and they got a black mark from their teabag tin. I think they are going down the road of having it looking 'lived in and worked on' !
Good luck.

ninathenana Tue 16-Sep-14 07:54:17

DH suggests dabbing the mark with cotton wool soaked in a weak (tsp in 1/4 pnt water) bleach. Leave over night. Then wipe with damp cloth.

DH used to make piano carcases.

Elegran Tue 16-Sep-14 11:34:55

I should have said oxalic acid, not boric. Someone told me yesterday that the black stain was from the tannin attacking the wet metal and causing a film of rust, which then sinks into the wood. Oxalic acid is a chelating agent and can reverse this oxidation. I think it works a different way from bleach, which oxidises.

I have looked up oxalic acid and found that "Oxalic acid's main applications include cleaning or bleaching, especially for the removal of rust (iron complexing agent). Bar Keepers Friend is an example of a household cleaner containing oxalic acid. Its utility in rust removal agents is due to its forming a stable, water soluble salt with ferric iron, ferrioxalate ion. . . . . Oxalic acid is used as a bleach for wood, removing black stains caused by water penetration."

Amazon seem to sell it, so I think I shall try that before the bleach. Nanabelle's son might find it interesting too.

Thank DH for me, nina I shall try that. If I overdo it or get it on the surrounding area, it will bleach that, won't it, so I had better be careful.

Agus Tue 16-Sep-14 15:27:22

I have been using Bar Keepers Friend for years now Elegran. It is excellent for cleaning chrome but cannot be used on stainless steel. I have not had the need to use it for your problem though, so, sorry I can't be of any help. Good luck.

ps I buy it in my local ironmongers but sure I have seen it in supermarkets now.

Agus Tue 16-Sep-14 15:48:24

Just realised I do have possibly a similar problem to you Elegran. The circular cast iron feet of a coffee table on an oak floor has resulted in some black markings. I will have a go at them with BKF later and let you know the results.

ninathenana Tue 16-Sep-14 16:28:23

Yes Elegran you will need to make sure cotton wool is not to wet. Maybe a cotton bud would be advisable.

rosesarered Tue 16-Sep-14 17:20:41

Lakeland [shop/catalogue] sell Bar Keepers Friend.

Agus Tue 16-Sep-14 17:31:25

Success! BFK worked on the lightest stain. Two applications, a fair bit of elbow grease in circular motion then worked into the grain. Rinsed off with cold water and, stain gone.

Another deeper stain hasn't completely gone so I am leaving a paste of BFK on it for a while.

Elegran Tue 16-Sep-14 17:42:07

I am glad I brought this up now. Agus has benefitted too! I have ordered some oxalic acid from Amazon. when it comes I shall keep you posted on progress. I saw Barkeeper's Friend on there too.

Agus, could you put those little cork bits under the feet of your table to stop it happening again?

Agus Tue 16-Sep-14 19:58:12

I am also glad you brought this up Elegran. Better still, a solution was found and it is something we can do ourselves. Very satisfying smile

Since cleaning the floor I have been thinking about what protection to use. Cork is a good idea and as the feet are round, I am going to buy round cork coasters and cut them to size.

Purpledaffodil Tue 16-Sep-14 20:07:34

Agus our local oak/pine furniture shop sells ready made pads in various sizes to go on the bottom of chair legs, think they are cork or maybe thick felt.

Nanabelle Tue 16-Sep-14 23:48:01

Agus - I have just looked up Bar Keeper's Friends and it is ok to use on stainless steel. I used to use it when I had a cream sink; think I shall buy it again as it's so good. Might try it on our brass letter box. I will tell my son too. Thanks.

Agus Wed 17-Sep-14 00:12:07

Nanabelle it was Elegran who first mentioned Bar Keepers Friend and that it might be of interest to your son.

I have justs read the back of the bottle and it says that it does remove tea stains. However you were right about using it for stainless steel as long as it is not mirror polished.

Thanks Purpledaffodil I will have a look in our local pine/oak shops here for pads.

Elegran Wed 17-Sep-14 10:56:02

If it has oxalic acid in it it will remove tannin marks, so it should take off tea stains.

Agus Wed 17-Sep-14 13:52:12

The marks have gone from the floor. Just have to re apply some linseed oil to the wood plus put some pads on the feet of the table. Job done! grin

Thanks Elegran

Stansgran Wed 17-Sep-14 16:59:07

I have BKF . I have a red wine stain on a limed oak table . I looked on the net and there was a suggestion of bicarbonate with linseed oil. Has anyone tried this. I'm a bit anxious as I love the table but it's getting a hammering with the DGCs( not that they are into red wine yet)

Elegran Wed 17-Sep-14 17:37:19

Red wine has tannin in it. Maybe Barkeepers Friend would remove it?

Rowantree Thu 18-Sep-14 13:18:42

Could someone tell me what is the active constituent of Bar Keeper's Fiend?

Judgie Mon 13-Oct-14 14:54:24

It is quite toxic but very effective, I have used it on my oak work surfaces when they have been 'black marked' by wet metal.
The active ingredients are
Citric Acid Monohdrate, Sodium Carbonate and Oxalic Acid.

Elegran Mon 13-Oct-14 15:01:05

I had no effect on the oak coffee table I have been renovating, except to prove to me that it is veneer, not solid - the amount of water involved has not been kind to the veneer.

The mark is a bit paler, but still very noticeable. I have solved it by painting that square of the parquet black, and painting oak leaves onto it. I now have an absolutely unique coffee table.

jinglbellsfrocks Mon 13-Oct-14 15:41:18

I got rid of a water mark (caused by cooling cakes on wire tray) on my Oak dining table by using a warm iron over a bit of White vest material. Worked a treat.

Agus Mon 13-Oct-14 15:59:33

There's always a solution Elegran wink

Elegran Mon 13-Oct-14 16:48:05

How to hide a black mark - paint it black!

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