Mould stains - how to remove

[steck]

Hi,
I have a camphor laurel slab which has some mould stains on it. The timber is now dry, i think that the mould probably happened when it was first cut, maybe the slabs were stacked together. I have seen a similar thing in a peppercorn burl which I cut.
It appears as dirty greyish spots about 3-mm, spattered across the wood. I removed an extra 3mm of wood but they go quite deep.
Is there anything I can use before finishing with hard Shellac, which will fade these spots without wrecking the timber?

[durwood]

Try a bit of bleach, its about the only thing that will kill mould. as it may change the colour if too strong weaken it down and just do a small area first so you can gauge the results.

I had seveal hides of leather given to me which were mouldy, one dose of bleach and they have never come back.

[echnidna]

Blue stain usually goes very deep into the timber.
You will probably need a very strong bleach like Oxalic acid to remove them, but it will lighten all of the timber not just the blue stained section.

[scooter]

Per Bob I'd try a oxalic acid solution as well.


Cheers................Sean

[old_picker]

Just been plugging some misaligned holes with fiji mahogony. Wiped off the glue with a damp cloth and 5 mins later there was dark blue spots all over the place. This particular piece must be full of spores. I cleaned up another piece we use for a chopping board with bleach. Killed the mould but it looks awful now. I wouldnt put bleach on a piece I was using for a feature.

Is oxalic acid better??
Where do you get it??
what about into the microwave for a minute or two??
that should kill the little buggers......

[scooter]

Ray, I'm not a chemist but oxalic acid is a very different beastie to chlorine bleach.

Most paint suppliers will have it for cleaning/rejuvenating old timber.

Another thought is to try an oxygen bleach product such as napisan or a generic cheaper version, once again a different beast to chlorine bleach.


Cheers..................Sean

[steck]

I will do a test on a spare piece of offcut. I have already found out that the stain goes along the grain and through the whole piece of timber, so I only expect to affect the surface layer. If this doesn't work, I may have to try hiding the stains. The wood has plenty of dark feature, so I could cut off the lighter wood, but I love the contrast. Thanks for the suggestions. I will let you know the results.

[steck]

Well I put the mould removing suggestions to the test.
This is the original piece of timber
29376
This is what it looks like wet with water. It loooks worse wet with turps!
29381
As you can see from this edge view, the mould goes deep and has penetrated right through the slab.
29378
I treated one section with undiluted dishwashing detergent.
The next I treated with undiluted bleach (White King).
The next section was done with with Oxalic acid solution.
And then I just Karchered the last section.
All the chemicals were vigorously scrubbed and let to stand for 10 minutes.

THe results are:
29380

The detergent was useless. The bleach produced the best improvement but still far from perfect. The Oxalic Acid made some improvement and the Karcher had no effect.

The bleach had the best effect and If I left it longer or used a stronger bleach it might produce an acceptable result.

I am led to ask, If I used the bleach, would it have a negative effect on my final finish?
What do you think of the idea (if more bleaching fails, as I think it will) of staining the sapwood a darker color?

[scooter]

Steck, the bleach you tried (white king) is chlorine bleach, per my post I'd give oxygen bleach (napisan, etc) a shot at it.


Cheers.............Sean

[steck]

I will give the oxygen bleach a go. I just didn't have any at the time.
Thanks for your interest.