I have used gun blue on a chisel to blacken it. It works okay but the smell never seems to go away. It sticks on my hands days later after using a chisel that I used it on so I am giving up on that method of blackening. I have 75% food grade phosphoric acid that doesn't seem to blacken it enough.

Any ideas on how Japanese chisels are blackened?

thanks

Have you tried a hot blue instead of the cold blue solutions?

No I haven’t. Any recommended hot blue products. Does it smell at all? 

Gun Blueing is technically Browning. Controlled rusting, controlled with oil, to keep the rust at bay.

Urine works well for rusting.

Neil

1 pt Ammonium Chloride and 2 pts Lye ... to make your own hot bluing

Steve,

mixed? or do you treat with one and then the other?

also...

I was reading on here (I think) about multiple steamings of the piece followed by baking soda. I'm not sure if that is something anyone else has tried and if so how well did it work?

Do a search on Ebay for an item called Caswell Black Oxide kit -- really easy to use. I saw others on here post about it I believe - works good.

Most of the cold blues use phosphoric acid. Hot blues use salts. Look up Brownell's and Du-Lite. A lot more involved but a better finish.

Also look into rust bluing, a long process, but gives very good results.

Firearm Bluing and Browning  R.H Angier, Stackpole Books  has a bunch of formulas in it but it's and *oldish* book; 1936, and so assumes that the reader will take great care on their own when dealing with chemicals! I don't remember if it includes a black other than a very dark blue.

I tried to find some info on rust bluing and found a couple sources elsewhere but if you can point me to one on here that'd be great... the search filter is a little picky it seems.

The sources I found suggested quickly forming a layer of rust with a variety of different products(household acids or products meant for rusting) and humid conditions. Then steaming it in distilled water. Is there anything more to this method? it sounds too easy/simple but I doubt it is.

From what I've read so far, it sounds like hot blue/cold blue form a thin, not very protective, layer on the surface of the steel. Is a rust bluing method more protective/thicker. 

thanks for your patience--- I'm new to all of this

51 minutes ago, astevens said:

the search filter is a little picky it seems.

The best way to search on IFI is to ignore the native Search function. Use the web search engine of your choice (I use Google) and include "site:iforgeiron.com" as one of your search terms.

I see that you're fairly new here. Welcome to IFI! If you haven't yet, please READ THIS FIRST!!!

Our best results with bluing was to not go finer than 230 grit when polishing by hand. I didn't like using a power buffer, as I felt it smeared the metal more and closed the pores in the metal up.

You are working with metal. you are not going to get a deep penetration with any type of finish. The only way to get a thick finish would be to plate it.  I have firearms that date back to 1864 with original bluing still intact. With any object that is in use it will wear in certain spots. Give it a wipe down with a light oil, or some like the silicone products and rusting will not be an issue.

As to rust bluing, that process is repeated several times until the desired color is achieved. It is not a one pass project. Rust, card off rust, reapply solution, rust, card off rust, etc....

I believe the Japanese blackening refers to a process called Japanning used for tools and woodwork. It's painted on.

https://en.wikipedia.org/wiki/Japan_black

https://en.wikipedia.org/wiki/Japanning

I believe Sculpt Noveau has different chemicals to give metal a patina.  

Watching this thread as it is something I have been experimenting with for several months, no real success thus far.

Tried Jax Iron and Steel Blackener and my test piece was not that black, maybe I am not using it correctly.

Unripe persimmons, the really tannic kind, are used by Japanese to create a black patina on ferrous surfaces. They also mix fermented persimmon juice with iron dust to make a back ink.  I was unwilling to buy a bottle Caswells, but I remember some fruit and vegetables can really black a high carbon rustable knife, so I googled what fruit should I use to black/blue iron or steel and came up with persimmons and just so happens my neighbor has a tree next door.  So, experiment coming!  Nearly in season, too.   Can’t find anyone that has done it on YouTube yet.  I am still googling around for any info.

Welcome aboard Pia, glad to have you. If you put your general location in the header you'll have a much better chance of meeting up with other members living within visiting distance.

Interesting about Using green persimmon for Black patination of iron/steel. Please keep us posted on your experiments.

Frosty The Lucky.

On 9/9/2025 at 1:54 PM, Pia said:

Unripe persimmons,

Interesting, we have several trees so I'll try and beat the critters to them and experiment.

I can’t control the wind. All I can do is adjust my sails. ~Semper Paratus~

Makes sense if they're really acidic. The other one he's describing is almost iron gall ink - tannic acid and iron, although in the west it was mostly iron sulfate. Sometimes they'd add a little bit of another acid, like sour wine and a binder.

You get a pretty good patina on carbon steel knives just from cutting up tomatoes or onions if you don't clean them right after. Between that and running them through the dishwasher it's why my oldest kid isn't allowed near mine in the kitchen. Or my cast iron for that matter.

I patinated the Buck sheath knife I got for my 11th. or 12th birthday by slicing potatoes on a Boy Scout camping trip. Turned out wiping it off with a wet cloth wasn't good enough. That was maybe 63-64 when I stained it and it still shows clearly. I still love that knife, the blade is silly HARD, so hard most people have trouble sharpening it. Once sharp it stays sharp a long time with minimal dressing. I don't know what the steel is but it's never been silver colored, it was ash gray when I unwrapped it and still is. . . Mostly.

I've been hearing this for a long time but never heard a convincing reason. Granted, it can really screw up wood handles. What is your objection to putting knives in the dishwasher? 

Frosty The Lucky.

The wood handles is a big part. Had to rehandle a couple of my favorite knives, including a couple I had from my grandmother, so I really preferred the way they looked with the old handles. For carbon steel, I also tend to get flash rust, especially if it sets in there damp for awhile or went through a drying cycle. It comes off easy enough, but if I was going to scrub them, dry them and oil them, why take the extra step of putting it through the dishwasher?

They also tend to come out duller than they went in. I've heard various reasons for it - some blame abrasives or acid in the detergent, others the mechanical action and movement against other silverware dulling the edges. I dunno the actual reason, but I can certainly feel and see a difference when my kid runs them through the washer. Sometimes I can just hone them, other times I have to sharpen, especially the carving or chef's knives. I got one out of the drawer the other day after he put one up and it tore up a tomato and wouldn't go through an onion worth a darn - he wanted to know how I knew he'd put it in the dishwasher. I think it might be worse with the newer dishwashers that run something like a three hour or more cycle.

I wipe, rinse and dry my wood handled knives and put them in the knife block, the only knives I allow in a drawer are the ones that don't need to be sharp. Like any edged tool, how can you expect them to hold the edge if they're rubbing against each other? Same thing in the dish washer, knives shouldn't be touching anything but the plastic coated rack if the rack isn't coated they're edge up. I have never had a dish washer dull a knife, not once.

There have never been abrasives in dishwashing detergents, they have too many moving parts to deliberately introduce abrasives, it'd be like putting valve grinding compound in motor oil. Soaps and detergents are not acidic and never have been, even prehistoric wood ash washing compounds are alkaline / base. Claiming they are damaging anything in dishwashers are rationalizations made up by folk who don't like them. 

There's nothing wrong with hand washing dishes, it's certainly faster. The new water "conserving" dishwashers neither conserve water nor do an adequate job and take 2-3x as long and burn a lot more power. Ours takes about 2hrs 19min. it's less because when it's about 10min into the dry cycle I open the door and air dry them in about 10 min.

It's still awful, my old one took about 45mins start to finish but you had to put plastics in the middle rack or they'd melt. I'd love a commercial one!

Regardless you have to operate the machine properly, just like you can't drop half a dozen knives in a tub of soapy water if you don't want a blood patina on them.

I'm not trying to convince you to use a dish washer or asking your reasoning. Use what you wish but don't wave BS rationalizations in my face about my decision being wrong. I wouldn't use one if it didn't work. PERIOD.

Frosty The Lucky.

Not sure how my dishwasher handles knives... i will ask her when i get home from work. 

On 9/18/2025 at 9:55 AM, Frosty said:

Use what you wish but don't wave BS rationalizations in my face

I never called your decision wrong, nor would I; do whatever works for you. I don't know if I've ever been that invested over other people's flatware cleaning unless they run a restaurant. I use a block, two blocks actually for my most frequently used knives. I keep some in a drawer as backups or because I don't use them often, and they're kept a little apart from each other on a dishtowel so they don't slide around and bump into one another. I probably oughta make one of those wrappable pouches that chefs use to save space.

As before, my kids don't have a lot of chores, but they're the ones doing the dishes most of the time and they do them about like you would expect for teenagers. Hence, they ain't allowed to load my knives or wash my cast iron. I don't know if the dishwashers save much or not, but I'd prefer one that used 20 percent more electricity and took 45 minutes over one that takes 3.5 hours and saved a small amount of water and money any day of the week.

Totally agree that the soap part would be alkaline overall, but I know at least one detergent that uses citric acid too, supposedly to cut down on mineral scale and balance the pH levels. Either way, I wouldn't think it would damage an edge. I got curious and spent entirely too long chasing down ingredient lists and msds sheets on detergent to see what's inside. I wasn't expecting salt, for one. After a little while in the rabbit hole, I think some of the complaints may have stemmed from phosphates in the older detergents etching cheap glassware.

Sorry about over reacting like that but I've been excoriated for using a dishwasher and almost never hear anything but the usual "reasons". Heck Alton Brown repeats them and he's been a professional chef for 30-40 years.

I owe you an apology, I should know by now not to bring up dishwashers it's too much a hot button topic. I must've been having a day.

Citric acid is a powerful cleaner and yes there are dish soaps containing it and they're my favorite for sink washing now they've eliminated phosphates and detergents just don't cut grease anymore. 

I don't know if there are dishwasher detergents with critic acid but for really greasy stuff I can't wipe enough out I'll squeeze half a lemon in the bottom of the washer. I keep a number of lemon halves in the chest freezer on the porch. 

Lemon is the BEST way I know of for getting the tea tar asphalt out of my iced tea jug, Thank you Slag I hope you're doing well. Let it dry and give it a good rub with a cut lemon, the squeezy of juice doesn't work nearly as well as the lemon rub. Leave it set for a few minutes then give it a coat of baking soda and a brisk rub with a sponge and it's clean.

Dish washer doesn't touch tea pavement worth spit if at all.

Anyway, once again my bad. You are more than welcome to throw dirty cyber socks at me, I won't even dodge. 

Frosty The Lucky.