Removing "grey" wood under varnish?

[Seagreen]

OK this is related to the mast issue. Having scraped the mast, I have residual grey patches (not huge but numerous) where the varnish has crumbled and left the wood exposed. Are there any useable methods for getting rid of these by using some chemical compound or other?

My usual route is to sand back to fresh timber but this would be a huge job so yes, I'm looking for a shortcut. I did hear that soaking and scrubbing with Sodium Bicarbonate (works on furniture apparently) may be an idea. This is a perennial problem with a lot of shiny brightwork, and once I start to skip it, it gets a bit ragged.

Any thoughts?

 

[Lakesailor]

Hard work isn't it? You don't say what wood it is but oxalic acid may do the trick.

 

[Woodlouse]

You will need to give it a thorough sand, 120 grit should do it, just to get the surface layer of discolouration off. Then a strong oxalic acid solution should then do the trick. If you can get oxalic acid crystals then mix them in hot water until they stop dissolving that is the strength you need. It may require more than one application as it dries as it only remains active when it's wet. Then rinse it off and varnish it up again.

 

[Seagreen]

Oxalic acid! As soon as I turn 50, my memory turns to mush.

I presume I can order this over the counter from boots, or an online supplier. Fantastic. Cheers for that.

 

[davidej]

Agree with oxalic acid but it may leave the wood looking very blond and you may want to stain it if you want a rich brown colour.

 

[prv]

I presume I can order this over the counter from boots, or an online supplier. Fantastic. Cheers for that.

I suspect Boots will just give you an odd look (they're basically a cosmetics and medicines shop now, not a "chemist" in the true sense) but there are plenty of suppliers on eBay with good prices.

Pete

 

[alant]

OK this is related to the mast issue. Having scraped the mast, I have residual grey patches (not huge but numerous) where the varnish has crumbled and left the wood exposed. Are there any useable methods for getting rid of these by using some chemical compound or other?

My usual route is to sand back to fresh timber but this would be a huge job so yes, I'm looking for a shortcut. I did hear that soaking and scrubbing with Sodium Bicarbonate (works on furniture apparently) may be an idea. This is a perennial problem with a lot of shiny brightwork, and once I start to skip it, it gets a bit ragged.

Any thoughts?

Make sure any wood is completely dry before revarnishing.
Its the vapour from any 'damp, when any sun is on it, thats lifting the old varnish & causing the wood underneath to go grey.

 

[Lakesailor]

Get it on-line http://www.agwoodcare.co.uk/index.php?id=106

 

[omega2]

If your a gardener then rhubarb leaves boiled up do the trick, throw the leaves used the liquid.

 

[Seagreen]

Lakey, it just so happens I've ordered 5kg of the stuff from them. Gives me something to do other than tossing the bunting this weekend.

 

[Deleted member 36384]

Use the Oxalic Acid before any sanding. If the stain is removed then just prepare for varnishing with the usual sanding. The risk with sanding first to remove the stain is that you might end up with a depression that was unnecessary.
Regards,
BlowingOldBoots

 

[Seagreen]

It depends if the Oxalyic gets here by saturday morning. I was just going to give it a light standard sanding rather than leaning on the sander. Then all I need to do is soak in acid, see the results, repeat or re-sand.