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Blackening steel parts

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Ron Laden29/11/2018 10:45:22
1094 forum posts
168 photos

I didnt expect such a response, very much appreciated.

I think it will have to be a cold method as one of the first parts to black will be the 40mm diameter flycutter I am making and I cant see my small gas torch heating all of that to red. Also some of the homemade chemical mixes I dont fancy using but that is just me, I,m sure they work fine.

Thanks again guys


Jon29/11/2018 13:17:18
988 forum posts
46 photos

The off the shelf blackening kits are ok for screws and threads thats about it. Goes on wafer thin and wont last 5 mins. its just meant as an immediate touch up.

The proper cold black you wont be able to obtain, its a closely guarded secret and would have to buy 20 gallon. Parts still need to be heated up to boiling and you paint the blacking on then wipe off building the layers up over 7 or 8 goes.

Hot blackings rather different around 150 - 155 degrees but no good for lead soldered parts. Easier to get hold of though would have to buy a bag of salts approxx £120 assuming they dont want to see your license.

Someone mentioned why buy cold black when oils free or words to that effect. Ones burnt on carbon the others chemical.

Other method to get colour in is just warm the part/s up from 230 to 285 degrees. OK for unhardened parts as it will do any tempering in ie whale oil burns around 150 degrees.

Ron Laden29/11/2018 13:55:24
1094 forum posts
168 photos

I dont know that I understand all of that Jon and from what some of the guys have suggested plus the links from Weary I was under the impression that the cold kits do work and not just on tiny parts..?

As for using Whale oil..? I could never do that, even if it was available which I doubt I would not be able to live with myself.


Edited By Ron Laden on 29/11/2018 14:10:06

Neil Wyatt30/11/2018 14:43:29
16066 forum posts
675 photos
73 articles

The practical difference between chemical blacking and oil blacking is that the chemical versions cause very little dimensional change.

Oil blacking is great if you don't need to be accurate to the last thou.


Graham Meek30/11/2018 17:33:13
95 forum posts
92 photos

A product I have used with some success is Curator Antiquing Fluid Black. While it is intended for brass the makers say it will work on steel. I must admit I was sceptical when I first read that, but as you can see from the photograph the finish is respectable.

Being a cold process it will never compete with commercial hot salts blacking, but for the odd occasional usage the product is hard to better for the price.

The fluid can be applied neat or the fluid can be diluted 10:1 and the parts immersed for 2 minutes, this is my preferred method. A coat of Shell Enisis after rinsing and drying with an air line is all that is needed.

De-greasing is the key, and I usually use Isopropanol followed by a hot wash in washing up liquid followed by a hot rinse. Rubber gloves are a must.

The photograph of the dial was taken 2 years ago and there are no signs of the blacking wearing off. The dials on the "Myford S7 Tailstock Micrometer Dial" thread were done using the same process.



fig close-up of dial graduations.jpg

Edited By Graham Meek on 30/11/2018 17:33:51

JA30/11/2018 20:02:26
733 forum posts
40 photos

I posted this question a few years ago.

I was unsuccessful in finding a company that would hot black mild steel (using caustic soda) so I did some trials. I found that I could successfully black screws and nuts down to 12BA by the blacksmith method.

I did over 200 items smaller than 4BA without a scrapper: Heat each item, held by steel wire, individually to red heat in a flame of a cooker gas ring and drop into clean 32 hydraulic oil. Simple but boring.

Since then I have found a firm in east Bristol that will hot black mild steel.


Stuart Bridger30/11/2018 21:17:58
299 forum posts
17 photos

Reading up on the cold blacking processes described here. They seem very similar to industrial phosphating that most of my apprentice pieces were subjected to in the '80s. Although I suspect the chemicals were stronger then. Everything is rust free despite being stored in damp garage for 30+ years .

Jon30/11/2018 21:49:12
988 forum posts
46 photos

Depends how good or bad a job you want. If your sights are low use cold blacking, wont last if handled or used it goes on wafer thin and patchy. On a positive anyone can do it, to make it look good smear an oil residue on which masks the patchyness some what.

Theres dozens of legit UK companies that will hot black all over England, Wales and Scotland. Some will do proper cold blacking not the gel stuff in kits.

Another point is you wouldnt oil black a quality part, that best done by hot browning/blacking/blueing whatever you want to call it.

Dont get confused between the cheap cold blacking kits approx £5 a small bottle to the proper cold blacking that runs at 100 degrees. Ones quality the other just a make do for low esteem.

thaiguzzi01/12/2018 05:03:29
530 forum posts
108 photos

Odd one out here (as usual).

Had great results on steel with USED diesel oil.

Mineral, not synthetic.

Steel component heated up on the gas cooker, purple to grey, then straight in the room temperature oil. Left overnight or at least a few hours.

Ron Laden01/12/2018 08:33:52
1094 forum posts
168 photos

Thanks again for all the advice guys.

I have ordered 500ml of Patination fluid so I will see how that works out. A question, once the diluted solution has been used can it be kept in a container and used again or is it just a one shot thing.


Graham Meek01/12/2018 10:24:15
95 forum posts
92 photos

Hi Ron,

I use 20 ml of the fluid at each mix, I also use distilled water from the shop dehumidifier, not tap water. Kept in a sealed container, such as a small square plastic sandwich box, I have kept the solution for over 12 months. However my usage is very small, 3-4 items per year, but they are relatively large items. Towards the end of the solutions life the blacking takes longer.

For my requirements this is more economical than some of the other cold systems, plus I can use it on brass.



Brett Hurt01/12/2018 10:45:43
23 forum posts
5 photos

Look at this that is what I do

Jon11/12/2018 22:36:56
988 forum posts
46 photos

Ron its not about whether it works, its about the finish and longetivity you will get from the off the shelf bottled or gel kits.
Dont confuse that with the proper 'cold blacking' that the parts have to be heated up to boiling at least 7 times and rusted each time.

Ron Laden14/12/2018 16:23:06
1094 forum posts
168 photos

My first attempt at blacking, seems to have worked ok but whether the finish will last I will have to see.


Vic14/12/2018 16:51:42
2097 forum posts
10 photos

I’ve used Gun Blue many times and it works very well on small parts giving a very deep black. I find heating the parts a little and them immersing them in the liquid works best. An oil coating afterwards helps protect the surface. Bigger parts are not so easy unless you can afford to buy a gallon of the liquid (it’s not cheap). What I’ve found is that the surface finish hugely effects the blacking process. I’ve personally found shiny or polished parts are much more difficult to black than sand blasted parts. In fact I seldom seem to black parts these days, I just sand blast them then wipe them over with Microcrytalline Wax. Have a look at the pictures of the tool holder in my album. At least one person thought it was a computer generated image.

Michael Gilligan14/12/2018 18:05:58
13230 forum posts
578 photos
Posted by Vic on 14/12/2018 16:51:42:

... Have a look at the pictures of the tool holder in my album. At least one person thought it was a computer generated image.


Hands up ... It was me blush

... and I remain astonished by its loveliness !!


Vic14/12/2018 19:11:07
2097 forum posts
10 photos

You weren’t the only one Michael, several others on another forum thought it was a computer generated image.

Nigel McBurney 114/12/2018 19:27:27
570 forum posts
3 photos

I aquired a Frost Auto Restoration blackening kit about twenty years ago,and I still use it occasionally mainly for stationary engine restoration,it still works ok,During apprenticeship days large parts were sent out for "chemical Blacking" probably not so good nowadays due to all the various modern controls and regulation. Small quantities of BA steel instrument screws were oil blacked by putting them with clean lubricating oil in a tin lid over a bunsen burner warming then up until the oil caught alight then let the oil burn off,they were NOT heated to red hot,as this would have ruined the polished finish of the screwheads.

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