Bleaching Wood

[BradNaylor]

I'm making a piece from English Walnut at the moment to match as far as possible the client's existing furniture.

Unfortunately the beautifully figured boards of walnut I managed to source locally are a bit too dark. They are kind of halfway between the golden colour we want and the 'purple' colour you see with American Black Walnut.

The client was in the other day and we were discusing the problem. He took a sample of the wood away with him and brought it back on Friday afternoon... exactly the right colour!

He'd taken it to a French Polisher who had bleached it and stained it to the right colour. I have to say I was stunned; I had not known that such a thing was possible.

I immediately phoned Morrells and ordered two different systems of wood bleaching - Oxalyc Acid and an 'AB' Peroxide kit. They will arrive on Monday and I will have a play with both.

I am sure they will come with instructions, but does anyone have any experience with using these products? The restaining bit doesn't worry me at all - I am quite skilled at that - it is the bleaching process I have absolutley no experience of.

Thanks in advance. My professional pride is at stake here!

Brad

(Also posted in the 'Finishing' forum)

 

[JonnyD]

Hi Brad

The A/B bleach is stronger than the oxalic acid. The oxalic acid is better for removing stains watermarks etc wheras the A/B will change the colour more evenly allowing you to stain to a consitent colour. I think i would use the A/B mix myself.

The process for the A/B bleach is let the A part soak in then apply the B part. Rubber gloves are essential as the B part is quite highly concentrated hydogen peroxide.

I think the best advice is to practice on some scrap timber to hone your skills but its just really a case of applying and waiting.

cheers

Jon

 

[MikeG.]

I've shied away from bleaching myself, but understand that there is a neutralising process to go through as well. Presumably you would ruin any finish if it were to come into contact with the bleach in the timber.

Mike

 

[Chris Knight]

Brad,
Oxalic acid,as Jon says is OK for watermarks, black stains on oak etc but it doesn't affect the heartwood colour - A/B type bleaches (caustic soda/peroxide) do. Having a peroxide component means the shelf life is shortish for this stuff.

Two short applications are much more effective than one long one in bleaching wood, so be careful if you think the first application was too weak - a second could overshoot the mark.

Because of the caustic content particularly, you will need to rinse off after bleaching - and wear gloves!

It's helpful when dealing with small areas to make an applicator by wrapping the end of a flat stick with a few layers of cotton cloth.

Sunlight will also bleach walnut and that can introduce a problem with colours differentiating over time if you mix naturally faded wood and bleached wood, even if they were accurately matched to start with.

 

[JonnyD]

I've shied away from bleaching myself, but understand that there is a neutralising process to go through as well. Presumably you would ruin any finish if it were to come into contact with the bleach in the timber.

Mike

I usually neutralise with water.

Jon

 

[OPJ]

What was it my tutor once said?...

Oh, yeah! Avoid bleaching wood at all costs!!!

That's not to say 'it cannot be done well', of course. It just might give you a few headaches along the way. It doesn't sound as 'straight-forward' as staining...

But, I hope it works out well for you, Brad! :wink: It would be a shame to make a mess of that walnut - is this the same stuff you bought for a few pennies the other week?