which acid/s exactly is the etchant composed of?
Here's the MSDS for Radio Shack PCB etchant--ferric chloride, ferrous chloride, and hydrochloric acid.
Now is not the time to bother me. And it's always now. Wiley Miller
primarily Ferric Chloride, Joels. I have etched carbon steel and wrought iron exclusively, so I use FeCl diluted with water, around 4 parts water to one part PCB etchant. You would need stronger stuff for any type of stainless. The slower you etch, the more detail you can pull out of say a hamon. You might dip a blade like that for 10-15 seconds at a time in the diluted FeCl solution and neutralize, rinse and polish off the excess oxides 10, 15 or more times. One the other hand, for a realtively shallow etch on my 1084/15N20 damascus like I used for the gyuto I posted recently, it might on ly one or two etches of no more than 5 minutes and a bit of Simichrome or Flitz and some elbow grease to finish that up. I think that I did one 5 minute etch and then a very short 1 minute etch on that gyuto because I removed the nail polish covering the makers mark and etched it lightly just to give it a tiny bit of color. I was VERY bright silver compared to the rest of the blade befoe that second etch, but I just wanted it to be a bit blue-gray, not to show the pattern inside the oval..
Uhm, so is it right to say the initial preparation involves polishing the sides of the blades to remove scratches that would otherwise be magnified by the etching process? Would it be feasible to do it with a sufficiently high grit stone (say a 6k) or the sandpaper has some inherent qualities that makes it better at the task? Btw thanks heaps Dave for sharing your knowledge!
The etchant will remove some light scratches and buff marks but it's best if you can sand the surface smooth and make it even in appearance before etching. It sucks to etch a blade and find a deep scratch still showing.
I would NOT use stones to do this work. Stones are flat and blade sides are not and you will without a doubt hate yourself for having tried the stone method. Sandpaper is flexible and will go in and out of the low and high spots.
Got the message! One day I'll find the courage to etch my Hattori HD... posts like this one are great to boost interest and push ppl to experiment, thanks again!
Can you over-etch a knife? If so what are the results?
You can forsure over etch a knife. I "forgot" I had a knife in my enchant and went hunting for a week. Now, this is a worst case scenario, but lets just say the blade looked like you pulled it out of a swamp after it being there 100 years. I did manage to salvage some of the damascus, but the acid ate so deeply a 240 mm gyuto I was etching ended up being a petty by the time I ground to clean steel.
I am new at this game, but everything that I see says that you can " over etch" a kitchen knife even if you don' t go to the extreme described by Pierre. With other types of knives, you might want to etch really deep, especially if you plan to "fill the low spots" by parkerizing or using baking lacquer to enhance the contrast. That might not work so well on knives used for food prep.