Oxalic Acid - or "In praise of Rhubarb"

[Good Surname or what ?]

Just received this email from a friend. As you'll see he had a problem with an unsightly stain. He called for advice and I read to him from one of David Charlesworth's books. It seems to have done the trick.

Hi Phil,

Great news!

Now, not only can you eat it in your crumble, your pavlova or melba but you can also use it to rescue your oak window frames. This wonder vegetable continues to exceed all expectations!

As you know, the problem was self-inflicted - wire wool used to dress the interior of the frames. The (ferrous) wire dust blew outside onto the cill and, aided and abetted by rain, inked the oak cills in a pretty gun metal blue - from end to end.

To remove, I applied the oxalic acid for about 25 minutes (applying more as necessary) and when the last stain had gone, neutralised with Borax in water.

Fantastic.

And, it just when you think it can't get better - it does.

Not only did it remove the ink but also cleaned off the fly **** - its a miracle cleaner! Listen mate, this stuff is hot. When the news gets out prices are heading to the moon. I've just dumped, I mean sold, my Iraqi Dinar holdings "at market" and moved into Oxalic acid futures - that's where you should be putting your money.

I can honestly say, Oxalic acid has changed my life.

Cheers,

A

PS You don't think that last line makes me sound a bit, kind of, anoracky do you?

 

[Jeff Gorman]

Reference to food and oxalic acid in the same message prompts me to offer the respectful reminder that oxalic acid is a nasty poison that does irreversible damage to the kidneys. I don't know what would be a fatal dose.

Our garden rhubarb is now finished so I can't try the idea, but I wonder whether, since rhubarb is associated with this acid, juice of the fruit would have any effect on wood stains?

Maybe stewing the leaves might produce a usable solution?

I think I recall that during the war, a radio program offered a recipe involving rhubarh leaves that lead to at least one death.

 

[Good Surname or what ?]

WFT,

You make a good point. I was always told, as a child, that the leaves are poisonous.

 

[brianhabby]

I needed to remove some stains recently and asked advice on this forum (here) about removing stains with oxalic acid. I eventually found some at John Penny. The instructions are very clear about the poisonous nature of this material - there's even a skull & crossbones on the label :!:

regards

Brian

 

[keithhickson]

WFT,

You make a good point. I was always told, as a child, that the leaves are poisonous.

They are even though the stems aren't. Also don't use the leaves on your compost heap )haven't got one but was given this advice a while ago)

 

[dickm]

They are even though the stems aren't. Also don't use the leaves on your compost heap )haven't got one but was given this advice a while ago)

Sounds a bit too cautious to me. The bugs in the compost heap will make shortish work of the oxalic acid, unless you had nothing but rhubarb leaves.

But in terms of woodworking, has anyone tried extracting the acid from the leaves to bleach timber?

 

[David C]

Have always understood that it was the leaves which were poisonous.

Oxalic acid solution is extremely useful and I wrote it up in my third book of articles, "A guide to Handtools and Methods".

One of the best applications is the removal of muckiness on oak and other timbers high in Tannic acid for those with rusty hands, also removal of blue black stains caused by certain glues and presence of iron clamps.

It should be available from all traditional polish suppliers.

David Charlesworth

 

[Inspector]

Oxalic acid is found in a lot of the foods we eat although in far smaller concentrations than in the product used to remove the stains.

You'll find it in addition to the rhubarb, in strawberries, chocolate, nuts, tea, wheat germ, spinach, and more. How do I know? I had a blast of a time with a kidney stone that was made of calcium oxalate. The above are on the don't overdo (for me at least) eat list, the dietitian at the stone clinic gave me. Since I don't ever want to go through that pain again, it's one of the few things a women ever told me to do that I've obeyed. 8-[

 

[Harbo]

David C - would it work on Redwood?

I have been gluing some Wellingtonia (giant redwood) with Titebond III which has stained blue wherever the glue has made contact - despite wiping off immediately with a damp cloth!

PS I now know why this wood is not used commercially - what a pain to work on - but I will not be beaten!!

Rod

 

[Harbo]

Further to my previous reply here's a photo of the staining:

Not having any oxalic acid to hand, I experimented on a scrap piece with "Milk Stone remover" - phenolic acid - worked a treat - stain gone in a few seconds. Do not know what it will do with the timber long term though?
Washed it off with water asap.

Rod

 

[Chris Knight]

Rod,
Milkstone Remover is concentrated phosphoric acid, not a phenolic acid. Similar to Jenolite which is no longer produced.

 

[Harbo]

Waterhead37 - you are quite correct - I knew it began with a "P"

It's the age?

Perhaps other acids work too - might have a go with some lemons?

Rod

 

[David C]

Harbo,

'fraid I don't know nothing about Redwood, but I don't think it would do any harm.

Oxalic is a mild bleach so if you do use it, it is better to do the whole surface rather than the local patch.

I find wiping surplus glue off naked timber to be problematical. A thin residue is driven into the grain wher it lurks un noticed untill finish goes on! A good scrub with toothbrush (or similar) after wiping, seems to work better for me.

Lemon juice once removed blackberry stains from Cedar of Lebanon for me. Recipe suggested by wonderful old lady violinist in local shop!

David

 

[Roy Clarke]

Similar to Jenolite which is no longer produced.

http://www.jenolite.com/






.

 

[Chris Knight]

Roy,
Thanks. I thought Dow Chemical had bought it and killed the product in favour of their own more expensive stuff - seemingly I was mistaken.