# Etching with coffee?



## mark76 (Oct 11, 2014)

On another forum I asked the question how I should etch a laminated carbon blade (plain laminate, no damascus). Apart from the "normal" answer, with ferric chloride, I also got another answer: strong coffee.

At first I though this was a joke. Then someone provided a pic of a knife etched with coffee. I then thought it was a sediment of the coffee on the knife that darkened the blade. But then more people chimed in, with pictures, and told me the color change was durable. 

Here are some pics from that thread (knives by Toni Oostendorp/Guido van Poppel).

A knife etched with ferric chloride:







The same knife, but now etched with coffee (rightmost knife): 






Another blade etched with coffee:






My question is: what happens here chemically? Is it etching what happens? And how durable is this etching or whatever happens?


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## EdipisReks (Oct 11, 2014)

Coffee is acidic.


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## mark76 (Oct 11, 2014)

That is correct. But only barely. Just a little bit more than cow's milk, but less than, e.g., beer. Still we don't etch with beer.


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## Tall Dark and Swarfy (Oct 12, 2014)

The most powerful acid in coffee is phosphoric acid which is a commercial etchant. Or perhaps it's creating a very thin phosphate conversion coating?

Cheers,

Rick


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## Benuser (Oct 12, 2014)

I use dabbing with hot strong coffee to force a patina on previously degreased carbon blades. Results may vary with the used coffee, though. Remember it will dull the edge as well, so clean the very edge immediately by slicing softly in a piece of cork.


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## Casaluz (Nov 13, 2014)

Pardon my ignorance... what does etching do or what is it? why would you want to do it or not do it? are there any threads on this?


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## Benuser (Nov 13, 2014)

Some use etching to revive a damascus pattern. But most common use is forcing a patina with carbon monosteel blades to protect against active rust. Search for patina.


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## Casaluz (Nov 13, 2014)

Ok great, thank you


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## toddnmd (Nov 13, 2014)

Hot vinegar is another way to do an etch with a common household supply. The knife will probably need a touch up afterwards, as the acid does also act a bit on the edge.


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