pinnerite <[email protected]> wrote:

I have a "solid oak" desk/bench top. I use the "" because it is made
from compressed wood strips (how do they do that?).

Some time ago I placed a rubber-covered torch/flashlight/lantern face
down on the top intending to replace the batteries or bulb when I
could find a way to open it non-destructively.

That never happemded. Finally I gave up and chucked it away.
BUT it left a raised ring of black "stuff" that I could not shift
without sanding.

Eventually the surface was smoooth but a black ring remained in the
wood.

I tried everything I could think of finally resorting to bleach.

Well, the ring went whitish but the area within and without became discoloured, some of it quite dark.

Oxalic acid might be the answer, it's certainly the way to fix stains
caused by iron/rust in oak. Rhubarb leaves contain oxalic acid but I
think you can buy it in a bottle specifically for clearing black
stains on oak.

--
Chris Green
·

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On 09/04/2025 18:50, pinnerite wrote:

I have a "solid oak" desk/bench top. I use the "" because it is made
from compressed wood strips (how do they do that?).

Some time ago I placed a rubber-covered torch/flashlight/lantern face
down on the top intending to replace the batteries or bulb when I
could find a way to open it non-destructively.

That never happemded. Finally I gave up and chucked it away.
BUT it left a raised ring of black "stuff" that I could not shift
without sanding.

Eventually the surface was smoooth but a black ring remained in the
wood.

I tried everything I could think of finally resorting to bleach.

Well, the ring went whitish but the area within and without became discoloured, some of it quite dark.

HELP!

You would need to sand lightly to get to bare wood, then treat with
dilute oxalic acid. (possibly several times). Wash carefully when done.
Allow to dry, give a light sand to smooth any raised grain, then
refinish with whatever you fancy.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/

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On 09/04/2025 18:50, pinnerite wrote:

I have a "solid oak" desk/bench top. I use the "" because it is made
from compressed wood strips (how do they do that?).

Some time ago I placed a rubber-covered torch/flashlight/lantern face
down on the top intending to replace the batteries or bulb when I
could find a way to open it non-destructively.

That never happemded. Finally I gave up and chucked it away.
BUT it left a raised ring of black "stuff" that I could not shift
without sanding.

Eventually the surface was smoooth but a black ring remained in the
wood.

I tried everything I could think of finally resorting to bleach.

Well, the ring went whitish but the area within and without became discoloured, some of it quite dark.

HELP!

Chris and John are right that the most common stain problem with oak is
a blue-black tannin stain normally from ferrous metals but also caused
by other things. The acid doesn't need to be Oxalic. Lemon juice or
spirit vinegar will work.

Cover the stain with kitchen paper or cotton wool, saturate with your
mild acid, then cover it all with cling film or polythene so that it
doesn't dry out, and leave it overnight to work. Literally rinse and
repeat if necessary.

TW

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On 09/04/2025 20:04, Chris Green wrote:

pinnerite <[email protected]> wrote:

I have a "solid oak" desk/bench top. I use the "" because it is made
from compressed wood strips (how do they do that?).

Some time ago I placed a rubber-covered torch/flashlight/lantern face
down on the top intending to replace the batteries or bulb when I
could find a way to open it non-destructively.

That never happemded. Finally I gave up and chucked it away.
BUT it left a raised ring of black "stuff" that I could not shift
without sanding.

Eventually the surface was smoooth but a black ring remained in the
wood.

I tried everything I could think of finally resorting to bleach.

Well, the ring went whitish but the area within and without became
discoloured, some of it quite dark.

Oxalic acid might be the answer, it's certainly the way to fix stains
caused by iron/rust in oak. Rhubarb leaves contain oxalic acid but I
think you can buy it in a bottle specifically for clearing black
stains on oak.

Don't forget that you need a Home Office Explosives Precursors and
Poisons Licence (EPP) to possess oxalic acid crystals or >10% solution.

<https://www.gov.uk/government/publications/licensing-for-home-users-of-explosives-precursors/licensing-for-home-users-of-poisons-and-explosive-precursors>

Odd for something widely available on Ebay and many DIY suppliers...

--
Reentrant

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