Strange colors after coffee etch

[Tyler.t76]

https://imgur.com/a/I817xHY

Got these strange colors after a coffee etch. Steel is 8670, it was first etched in ferric chloride, then I put it in an instant coffee mix for a few hours following instructions I found through YouTube. Anyone know what could have caused this coloration? Looks like a knife that was put to temper in an oven that still had oil on it. The steel was cleaned appropriately before the ferric and before the coffee. The ferric etch was completely normal so it had to be something with the coffee I assume. Any ideas?

 

[Stacy E. Apelt - Bladesmith]

You should clean the blade very well, etch for a long time in FC, DO NOT touch or clean the blade before placing in the strong coffee soak. Soak for many hours.

Tell us about the coffee mix you used. Temperature, type of coffee, concentration, etc.

 

[Tyler.t76]

You should clean the blade very well, etch for a long time in FC, DO NOT touch or clean the blade before placing in the strong coffee soak. Soak for many hours.

Tell us about the coffee mix you used. Temperature, type of coffee, concentration, etc.

I just dumped a whole lot in there, didn’t measure just put a lot. The temperature I took it to a rolling boil and stirred it and then let it cool enough that I could put a finger in it and put the knife in, didn’t keep it warm the whole time, I know some people say you should but I also heard it wasn’t absolutely necessary. The coffee was Kroger brand medium dark roast 100% Columbian ground coffee, was just the cheapest thing on the shelf at the time. The strange colors came off after a light scrub with steel wool, and the blade was still much darker than it was from just the ferric, my intention was to stonewash anyway so wasn’t really too worried how it turned out, it was mostly just me playing around with it. I’d certainly do research before I tried it on any pattern welded steel, but I’m not quite interested in swinging a hammer that much during this heat lol!

 

[A.McPherson]

I've only ever used instant coffee... Did you use instant or normal coffee grounds?

 

[Tyler.t76]

I've only ever used instant coffee... Did you use instant or normal coffee grounds?

It doesn’t say whether it’s instant or normal so I’ll assume normal. I know now you’re supposed to use instant coffee, I bought the tin of it several months ago just because I saw it for cheap. It seemed to work fairly good after a scrub with steel wool the colors left and it was much darker than the FC left it. Just a piece I was playing with before stonewashing so didn’t intend on getting it too dark anyway.

 

[A.McPherson]

Cool. I just wonder if the colors were from the oils in the ground coffee.

I bet instant has less oil in it.

 

[Stacy E. Apelt - Bladesmith]

I don't do coffee etches, but the folks I know who do use something like this:

Use the cheapest instant coffee on the shelf. Mix it crazy strong. Half a jar to a quart is a common concentration.
Soak for 2 to 8 hours. Don't scrub it off, just gently wash the blade with soap and water and let dry.

A coffee etch is not a user etch, as it is just a surface coating that will rub off and scratch easily. It looks good but is merely cosmetic.

If you want a fairly durable dark surface on a user knife, try Parkerizing of similar treatments.

 

[Michael Black]

I don't do coffee etches, but the folks I know who do use something like this:

Use the cheapest instant coffee on the shelf. Mix it crazy strong. Half a jar to a quart is a common concentration.
Soak for 2 to 8 hours. Don't scrub it off, just gently wash the blade with soap and water and let dry.

A coffee etch is not a user etch, as it is just a surface coating that will rub off and scratch easily. It looks good but is merely cosmetic.

If you want a fairly durable dark surface on a user knife, try Parkerizing of similar treatments.

I'd just add a technique I stole from Neil Kamimura's video to used compressed air to dry the blade straight out of the coffee (without touching the blade at all), then gently apply some carnauba wax and hit it with a heat gun for a bit, then hand buff with a clean rag. It makes for a pretty durable finish, although obviously it's not like Parkerizing, like you said. The knife below has been getting use in my kitchen for the past month or so and looks almost brand new still, despite being essentially just a forced patina. I'm a fan!