Copper Sulfate and Salt Etch Process



I've been fighting with ferric chloride and ferric nitrate etchants for awhile now. They're great for non-ferrous stuff, but for iron and steel I've personally been less than impressed. I also have gripes regarding asphaltum, lacquer, nail polish, and wax resists. Copper Sulfate/Salt etchant, however, is utterly amazing.


Definitions:


Resist/Ground: a coating applied to something to prevent an acid or other chemical from attacking it.

Etchant: A chemical that attacks a thing such as steel or glass.


The two examples in this image were etched in under an hour using the following recipe:


Etchant:


1 part finely powdered copper sulfate (use a mortar and pestle, wear a mask and all other PPE)

1 part non-iodized salt

enough water to make a wet paste


I measured the stuff with a kitchen scale. Also...the salt and CuSO4 act upon metal via electrolysis...do not store this in a metal container...it WILL eat it.


Resist (ground):


1 part rosin

2 parts bee's wax

3 parts asphaltum


To mix: use a double boiler of some manner to melt the wax gently. Once melted , add the asphaltum while stirring. Then slowly add the rosin until everything is melted and mixed. You're supposed to then strain this hot mix through cheese cloth into cold water, remove the hardened stuff, let it dry, and then remelt into a container. I didn't, but I'm lazy.



Get what you plan on etching and make a design. Simple. I traced the knife and then found a cozy place to work on the design.


To coat this knife with resist, I warmed it on the top of a fireplace brick facade. This got the steel to a fairly warm temp, but not so hot I couldn't hold it in my hand. This is important if you plan on etching after heat treat.



Warm your resist. I suggest re-heating in a double-boiler contraption. I used an old gnarly sauce pan with water in it, then set the tin of resist in that.



First go I got the resist too thick for my purposes.



To fix it, I put the knife in a metal bowl and very very VERY gently warmed it with a feathered torch flame. I used my smallest butane torch. This is not a job for an oxy/acy rig. The resist can and will catch fire.


I let the resist warm enough to flow off the knife into the bowl, being incredibly mindful of how hot the already heat-treated blade got. Don't get anywhere near temper temp. The resist will start to burn long before this, but still...just saying...be careful if you're doing this to a knife/weapon.



My method of transferring a design to stuff: SARAL TRANSFER PAPER, BITCHES. Ok, yes you can coat some regular paper with soft graphite or whatever...but this shit? It's like heavily-loaded carbon copy paper...thin, sexy, and capable of recreating fine details if you use the right tools. It makes my life vastly easier.


Also tracing paper...'onion paper' if you can find it.



From left to right: Original doodle...doodle on tracing paper....Saral transfer paper after being used (what looks like a drawing is actually the absence of graphite)...and final etch on mild steel.


NOTE: you want the dark side of the transfer paper down against the object to which the design is being put on. You can double-check you have the correct side by rubbing across your nose. The oils specific to your nose will turn the paper green. This last bit is a lie.



A more visual example of which way the transfer paper needs to go. Here I have the whole monstrosity layered as follows: knife (or ferrous item of choice), transfer paper (graphite side facing the thing to be etched), and tracing paper design template.



Tape that shit up nice and tight. Don't press too firmly, you'll rub graphite from the transfer paper off onto your item. DOUBLE CHECK YOUR ALIGNMENT NOW....seriously...I think one of the main reasons people give up art is frustration...being a little anal retentive helps a lot.



Don't forget to coat the backside, too. While the etch paste is thick, a little could drip down and etch something you don't want etched. Cover anything you don't want etched.


COVER ANYTHING YOU DO NOT WANT ETCHED



Start transferring your designs. There's fancy special tools for this. I made my own, though. A dried-out, crappy, uniball roller pen. Don't press terribly hard at this point...you're only wanting to get the design to transfer. You do not want to start removing any of the resist.



Presto chango! A thing with a thing on it. I...yeah, could have spent a little more time making this look nice but whatever, I'm a terrible person.


Ok, now you need to start removing the resist. Again, there are super fancy tools you can buy for this. I made my own: a sharpened hardwood skewer and a cheap harbor freight screwdriver turned into a scribe thing. (protip: pick up cheapo screwdrivers when you can, they suck for use as a screw driver but rock for being made into an insta-tool)



Here I've removed most of the resist. At this point you want to go back and clean up any spots that look jenky. You can paint on a little resist if you gone a little too crazy with the removal



Alrighty...the really fun part. Put the etch paste on. I used a stick to dab it on, utilizing surface tension to keep it where I wanted. Let this sit for about 20 minutes.



Use a cheap brush to 'stir' the etchant. It'll start turning brown as iron is pulled off. This is how I judge how far along the process is. This will differ based on alloy type, temp, etc etc...this is something you need to experiment with. Always do a test piece when you start using a new material. Get a feel for the process and your materials. Become one with them. (Don't ingest or inhale, though)



Also: don't leave your brush in the etch. Like I said...this stuff works pretty damn fast.



Here's the knife after about 30 minutes of etching. That red stuff is copper. As the iron is pulled off the object, copper settles on to it. You can use clean water and a brush to remove this. Cold water is good for dipping the object into...it makes the resist hard, at which point you can gently rub the copper gunk off with a soft, moist cloth.



All the copper gunk is gone, only the resist remains. You can now clean the resist off and call it done or you can add another dose of etchant for an even deeper etch.



Remove the resist with paint thinner and then acetone.



Boom....etched. Please comment below with any questions.

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