Bleaching wood before staining and varnishing

[M71]

Hi all - bleaching some finger jointed boards to get a consistent substrate color before staining and varnishing.

Got hold of some Hydrogen Peroxide and some Sodium Hydrochloride - instruction is to brush one on first and wait an hour before brushing on the other. Next day sand it off.

Can anyone tell me if this stuff will allow the stain and varnish to go on without any problems ?


Cheers

[Master Splinter]

You might be getting your chemicals mixed up - typically it's sodium hydroxide (caustic soda) that's used with hydrogen peroxide. The caustic soda opens up the wood to allow the hydrogen peroxide to do the bleaching. I have the feeling that adding hydrogen peroxide to sodium hydrochloride will do little except liberate chlorine gas (which will bleach wood, along with your clothes, hair, eyes, lungs.....)

Note that you need about a 30% hydrogen peroxide solution. The stuff sold for hair bleaching is only about 5%. Industrial cleaning supply places should have it at about 50%.

Keep in mind that hydrogen peroxide is used in rocket fuel so store it well away from anything that could be oxidised (that's not 'oxidised' as in 'made rusty' but 'oxidised' as in 'energetically and exothermically combined with oxygen'.)

PDF instructions:
http://www.fpl.fs.fed.us/documnts/fplrn/fplrn165.pdf

[ubeaut]

Think you'll find that any timber bleached with Hydrogen Peroxide will not take a stain after the bleaching is done.

Could be wrong but for some reason that info seems to be stuck firmly somewhere in the back of my mind.

Cheers - Neil

[M71]

Thanks for info - the link is very helpful indeed.

Ended buying 2 pack bleaching mix made especially for wood rather than take a punt with individual chemicals - works well and stains up nicely.

[yojimbo]

Hi -- my first post in the Finishing forum... been in Japanese Hand Tools forever. But I'm a professional finisher/refinisher. The thing to know about hydrogen peroxide is that it can remove all traces of grain from the wood, and there's no way to ever get it back.

Here in the US, when pushed, we use oxalic acid to bleach. Don't know if you might call it something different there.