September 05, 2015


A weekly column featuring random wisdom gems, fun facts and school lessons re-discovered.
Today: Why do vinegar, steel and tea age wood?

Did you know, when you brush wood with very strong (English Breakfast) tea, let it dry and then apply a solution made of steel wool dissolved in vinegar the wood turns a grey or even black-ish colour? Basically it makes the wood look like it has been lying outside in the weathers for years; only that this ageing didn’t take years but rather a few minutes.

Once I got over the excitement what possibility this little wood-working trick brings up, I couldn’t help but wonder how it actually works. What is happening with the wood and why does it turn grey? Google told me that the vinegar only plays a very minor role in this. It is really only the carrier of the iron from the steel wool. As it reacts slowly with the steel wool, it creates iron acetate, which is what really matters when you brush it on the wood. This iron is very acidic and reacts with the tannins (also acidic) of the tea (or even just the wood if it has a lot of tannin). Together they form iron tannate, which is dark in colour and insoluble and therefore stains the wood a dark grey-black colour.

There you have it, a little chemistry lesson for your weekend. On other matters:

Why is sneezing so satisfying?
Mindy Kahling on confidence.
I had lunch break with my favourite blogger.

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