Black marks/stain in grain

[benldwyer]

Howdy All,
Just a quick (probably silly) question, I have an unfinished flame QLD maple cap on a guitar and I sprayed it with water to bring out the grain and wood colour and after the wood dried I was left with a black stain in the grain covering half of the guitar...what did I do..? Is it because I used tap water?
Cheers in advance

[kiwigeo]

Can you put up a photo? Sounds like either something in the water or something water soluble on the wood that the dousing has spread around.

[benldwyer]

With water and after it had dried, you can see on the right hand side the staining isnt bad and I gave it a light sand wich seemed to work ok but there is still black in the flame so I stopped to see if I could find another solution rather than sand anymore..

[Trevor Gore]

That looks like staining due to a mix of iron and carbonate ions in your water reacting with the tannins in the wood (i.e. hard water plus iron plus tannins). A certain fix for that is to wash it down with a mild solution of oxalic acid in pure (de-ionised) water. Oxalic acid is available in crystal form from Bunnings as a deck cleaner. Don't use too much (a teaspoon of oxalic acid crystals dissolved in a cup of warm water is plenty) or you will end up with a red hue in the wood. Wash down afterwards with a mild acid solution e.g. white vinegar in pure water. You could try starting with a wash down of white vinegar in water and that may just do the trick. But if it doesn't, you now know what will work. Oxalic acid is a bit nasty, so observe the safety instructions on the container.

[kiwigeo]

That looks like staining due to a mix of iron and carbonate ions in your water reacting with the tannins in the wood (i.e. hard water plus iron plus tannins). A certain fix for that is to wash it down with a mild solution of oxalic acid in pure (de-ionised) water. Oxalic acid is available in crystal form from Bunnings as a deck cleaner. Don't use too much (a teaspoon of oxalic acid crystals dissolved in a cup of warm water is plenty) or you will end up with a red hue in the wood. Wash down afterwards with a mild acid solution e.g. white vinegar in pure water. You could try starting with a wash down of white vinegar in water and that may just do the trick. But if it doesn't, you now know what will work. Oxalic acid is a bit nasty, so observe the safety instructions on the container.

I was thinking the above but didn't think Queensland Maple was that high in tannins. I didn't consider high iron in the water.

[bobthebuilder]

Just a little aside, when I want to view the grain I spray with Iso Propal Alcohol you will find it at Bunnings it will high lite the grain then evaporate of with no residual effect. I hope you find this helpful. Cheers , Robert

[benldwyer]

Thank you All, I will give it a try and report back. I knew it was risky but was a little impatient... thanks again!

[benldwyer]

Hi All,
Sorry for the delay in responding, moved over to Perth for a new role.
The vinegar removed most of the stain but might have to try the harsher chems to clean it all up.
Cheers!