Etching Q.s

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cotedupy

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I know there have been a few threads about this, including a very helpful one from @Dave Martell a while back, but there were a few things I couldn’t find the answer to...

If tomorrow I were, hypothetically, wanting to bugger around with strong acids and banding, would the big container of 32% HCl I have in the shed be suitable? Would I need to dilute it with vinegar? Or water?

Or is Ferric Chloride better? And if so - can I make Ferric Chloride by putting wire wool in 32% Hydrochloric acid? Is Ferric Chloride the same thing you use to ‘ebonize’ wood?

Should the knife finish be left quite low beforehand (like SG500)? Or do I want to put a nicer finish on it and then etch after?

What does this kind of thing do to kuruochi? (Proper kind, not black paint).

TY for any insights!
 
If tomorrow I were, hypothetically, wanting to bugger around with strong acids and banding, would the big container of 32% HCl I have in the shed be suitable? Would I need to dilute it with vinegar? Or water?

Getting good etches on banding is more about the difference in corrosion resistance different alloying elements cause to different chemicals. Generally, less corrosive solutions will bring out this contrast a lot more than stronger ones. The other factor in etching is what sort of compounds are left on the surface of the steel. HCl has some oxidizing effect but it leaves more grey than black and for non-stainless steels Ferric is preferable. Many have also gotten good results with hot vinegar, lemon, coffee etc.

Or is Ferric Chloride better? And if so - can I make Ferric Chloride by putting wire wool in 32% Hydrochloric acid? Is Ferric Chloride the same thing you use to ‘ebonize’ wood?

Yes in theory dissolving steel wool in HCl will get you Ferric but It will give off a lot of really nasty fumes and I would recommend just buying Ferric. The chemical used for ebonizing wood is iron acetate, not ferric chloride.

Should the knife finish be left quite low beforehand (like SG500)? Or do I want to put a nicer finish on it and then etch after?

I would recommend a higher surface finish than that to get the best contrast 1k+.
 
I’ve got a lot less experience than others here, but have been playing around with this a good bit over the past few months. I’ve found best results with vitamin c and citric acid and doing many quick etches (no more than a minute) and alternating with gentle abbrasive, usually water down mud or finger stones between etched. After 10-15 rounds I usually get good results. I think higher levels of polish work best for this. @brooksie967 has coaxed some absolutely bonkers banding out of a Wat honyaki that I’m trying to emulate with my Kaeru, but I’m still a notch or two below that much pop and haven’t seen a guide for how to get there.
 
I don't have a ton of experience. But I'll echo something @Troopah_Knives said, you don't want to strong of a solution. You'll just get muted grey's.

Coffee looks nice, dark brown/black color. But isn't very durable.

I've tried different vinegars and I think balsamic is good for darkness. More durable than coffee.

Stainless you'd be better off with muriatic acid and ferric chloride.

0000 steel wool is a lifesaver.
 
I also don’t know what I’m doing with etching, but my massively oversimplified method is just cutting a hot lemon over and over. It seems to work better when I use a specific stone to pull out some preliminary banding/detail so I can actually see what I’m looking for.
 
32% Hydrochloric acid will be very nasty, dangerous, and fumy to work with. Hydrochloric acid and steel wool will make ferrous chloride and you need to add oxygen via hydrogen peroxide or a fish tank bubbler(I do some of both to avoid diluting the FC with too much water from the 3% peroxide) to make it into ferric chloride. While using ferric chloride is somewhat mild the reactions to make it are not and should be done outside with proper PPE.

Incidentally when you etch with ferric chloride you will be reducing it to ferrous chloride which can be turned back into ferric chloride with the addition of oxygen from the fish tank bubbler.
 
Shi-Han A-2 Ferric Chloride
My initial concentration 43%, mixed 1 part to 3 parts water sanded to 2000 grit

IMG_1169 2 Edited.jpg IMG_1171 4 Edited.jpg IMG_1173 6 Edited.jpg
 
1) Professional chemist here. Always add acid to water SLOWLY.
2) wear PPE and be in a well ventilated area.
3) ebonizing wood is iron acetate. Steel wool in vinegar… maybe iron chloride would wor.
4) see point 1 and 2.
 
Thank you all for your thoughts and insights here.

I had assumed that stronger acid was going to be better for this. I didn't know that weaker solutions were actually going to give more contrast and highlighting.

I've done various forced patinas with other stuff, just never on knives that have really noticeable banding. So I'll just go with that again I think. I quite like instant coffee made with hot white vinegar instead of water. But maybe I'll leave the coffee out this time as it does make things quite dark, and I'm trying to get the layers to really pop.

Cheers all! You've saved me from feckin' around with dangerous chemicals, which is good, especially as it's a pretty hot day here.
 
TY for any insights!
If your knife is carbon steel Damascus, ferric chloride is a good starting place. Its cheap and available on Amazon.
I use it mixed with water 50/50 but it works fine at other mix concentrations as well.

The level of polish effects the time it takes for the etch to work. More polish, more time.

For kitchen knives, I etch for 30 seconds, take the blade out rub it down with sand paper. I tend to go around 800 to 1500 for the finishes I like on my knives. After that back in the ferric for 5 minutes. Pull it again and sand again ( the sanding removes the oxide build up and allowed it to keep etching quickly ) When I start to see a slight shadow around the brighter steel I stop etching.

At this point where I go depends on what color contrast and what mood I want to set for the knife but often I will follow up the ferric etch by cleaning the blade really well and doing a light coffee etch to bring out a little contrast more than sliver and mat gray the cleaned ferric etch leaves.

If its stainless Damascus, ferric wont work. For that muriatic acid works.
 
What is everyone using as a container for the acid etch? Can a mixture of water and ferric hold over time or is it a one and done after the etch?
 
What is everyone using as a container for the acid etch? Can a mixture of water and ferric hold over time or is it a one and done after the etch?
I also use a piece of PVC pipe.

The ferric chloride will last by itself, but the act of etching does so by turning some of the ferric chloride into ferrous chloride. The ferrous chloride will no longer etch, but it can be turned back into ferric chloride with the addition of oxygen. (fish tank bubbler)

Ferric chloride is a brown color and ferrous chloride has a green tint.
 
A bit of an aside,
When I heard that coffee can work for forced patina, I grabbbed some used grounds, wrap steel/ coffee in a towel and wait 30min.
This didn’t last for long, maybe a longer soak, or repeated would last longer.
As for exposing banding or etching, is it easy to tell what is banding/ alloying from just visual inspection?
This polish is from a hindostan which i am brand new too as of 3days ago. This is on a highly polished gyuto with Tsuchime slurry.
 

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Alloy banding has a regular pattern that is almost like really tight and subtle damascus. It’s not something that shows up on most knives as most don’t have it. I’ve found best results showing it, if it’s there, using multiple quick acid dips on a highly polished blade, removing the bulk of the “patina” caused by the etch with whatever polishing substance I used for finishing. (Eg - diamond paste, etch, diamond paste, etch)
 
A bit of an aside,
When I heard that coffee can work for forced patina, I grabbbed some used grounds, wrap steel/ coffee in a towel and wait 30min.
This didn’t last for long, maybe a longer soak, or repeated would last longer.
As for exposing banding or etching, is it easy to tell what is banding/ alloying from just visual inspection?
This polish is from a hindostan which i am brand new too as of 3days ago. This is on a highly polished gyuto with Tsuchime slurry.

@Bear has a great example of alloy banding on his shi.han above. Here’s another shot of banding on my Markin in 52100. It does look very much like damascus, or I guess more precisely suminagashi. I’ve been waffling over doing a coffee dunk on this guy.

I’ve seen more than one experienced bladesmith say they can’t predict or control when banding shows - it seems to involve a fair amount of uncertainty.

3FE115C9-5941-4556-ABF3-71ABE22BB9FD.jpeg
 
1) Professional chemist here. Always add acid to water SLOWLY.
2) wear PPE and be in a well ventilated area.
3) ebonizing wood is iron acetate. Steel wool in vinegar… maybe iron chloride would wor.
4) see point 1 and 2.

And a way to remember #1... Add acid to water, like a fellow aughter.

I prefer, "always drop acid"
 
Off hand I would say that there is more than banding going on there. I wonder if @Kippington or anyone else has ever run into this much banding on their 52100?

I posted a few pictures many years ago, although they were faster hardnening steel than 52100.

If I'm honest, I am not a fan of alloy banding. It's something outside of my control. Whenever it shows up, it feels like an unexpected development, kind of like a unwanted impurity in the steel that you only find 25 steps into the making of a knife...

RlQGrSb.jpg


wzNwmfx.jpg
 
oxalic acid will blacken pretty much everything. even stainless cladding. oxalic acid is whats used in all rust removers.
its a powder that you mix and drink. no just kidding. dont drink it. its cheap too. should be available in pretty much all hardware/paint stores.
 
What is everyone using as a container for the acid etch? Can a mixture of water and ferric hold over time or is it a one and done after the etch?

most acids will stop working after a while. vinegar only lasts for like 30 minutes then i guess its saturated or something. oxalic lasts even shorter but the effect is much much stronger and faster. basically when the the bubbles stops its finished.

i put all my restoration razors in oxalic acid to convert rust to black oxide and its stops working in about 5 minutes or so. and the blades are all black then.
if you want the black oxide to become more durable/thicker you have to wipe them down and do 2 more dunks.

its not gonna be as durable as gas/coal forge kurouchi, nor oil quench kuro. but it is a black oxide.
 
I wonder if @Kippington or anyone else has ever run into this much banding on their 52100?
I do a lot of 52100 and haven't seen anything like that.

Here is a theory.

Many bladesmiths using kilns do a number of pre heat treat steps including 10 to 15 minute soaks to insure all alloying elements and carbides etc have gone into suspension before heat treating.
Many traditional smiths who use a forge for heat treating don't use soaks ( hard to control the temp over a long period in an open flame ).

I wonder if that has anything to do with banding?
 
I've gotten something similar to this with W2. Turns out this was because I wasn't normalizing the blanks from a high enough temperature. I'd read an article from a reputable bladesmith about normalizing W2 from 1600F and down in 25F degree increments for 3 cycles, but I hadn't taken into account at the time that this was in reference to forged blades, not ones cut from annealed sheets.

I started adding a cycle at 1750 first just to be sure, and problem solved.


1.jpg
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I do a lot of 52100 and haven't seen anything like that.

Here is a theory.

Many bladesmiths using kilns do a number of pre heat treat steps including 10 to 15 minute soaks to insure all alloying elements and carbides etc have gone into suspension before heat treating.
Many traditional smiths who use a forge for heat treating don't use soaks ( hard to control the temp over a long period in an open flame ).

I wonder if that has anything to do with banding?
My understanding of banding is that it happens at the time the steel is transforming from liquid to solid and dendrites are forming in the transformation boundary. Short of re melting the steel in a crucible, I don't think the smith has a way to change the dendrites. However, carbide formation can be controlled in the heat treat and carbides between the dendrites does effect the visibility of the dendritic structure.

Apologies to the OP for the off topic post.
 
Off hand I would say that there is more than banding going on there. I wonder if @Kippington or anyone else has ever run into this much banding on their 52100?

That particular knife is from a “budget” batch Andrey made where he reduced his normal level of fit and finish to hit a lower price point, so I doubt he did anything special that would require extra time beyond his normal standard forging and grinding. If you’re familiar with his work you can see the sophistication of the handle and level of polish on the blade are not to his typical high level (just killed my BST flipper resale value 🤣 )

We could ask Andrey but I don’t want to put him on the spot if it is indeed some kind of new process he’d rather not share. I haven’t noticed heavy banding like that on photos of his other knives, but this is the first I’ve owned from him.
 
I used FeCl diluted with vinegar, I etched multiple time for short periods of time, but I would be interested in trying longer etched on damascus in order to creat greater depth
 

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