Author Topic: Blackening (Read 23249 times)

shipto · « **on:** June 03, 2017, 12:42:07 PM »

first foray into blackening was almost a success, its good enough at least. The body was the last bit I did and seems to be the best finish this was done by setting my furnace to 360C and applying linseed oil once at temp then blowing excess oil away and then reheating till black.
I have put the worst bits in the final pic because I would welcome any input to make a better job next time I try.

PK · « **Reply #1 on:** June 03, 2017, 05:57:25 PM »

You was a selenium (cold) blackening process yes?

shipto · « **Reply #2 on:** June 03, 2017, 06:38:04 PM »

no heat at 360C and linseed oil.

PK · « **Reply #3 on:** June 04, 2017, 01:51:50 AM »

Quote from: shipto on June 03, 2017, 06:38:04 PM

no heat at 360C and linseed oil.

Well your results are better than I ever managed with heat and oil...
Here's a 'fresh from the bath' shot of the cold black process I use' Pretty sure I got it from Caswell.

chipenter · « **Reply #4 on:** June 04, 2017, 03:13:23 AM »

Surface must be clean fingerprints will show , I just heat with a torch and drop into used engine oil , works for me .

AdeV · « **Reply #5 on:** June 04, 2017, 05:34:19 AM »

I used Caswell's blacking chemicals on my QCTP, it's actually holding up very well... no recent pics I'm afraid, I'll see if I can grab on next time I'm at the workshop.

shipto · « **Reply #6 on:** June 04, 2017, 08:25:18 AM »

Quote from: chipenter on June 04, 2017, 03:13:23 AM

Surface must be clean fingerprints will show , I just heat with a torch and drop into used engine oil , works for me .

I think that may be the problem I did clean it off with turps before starting but maybe should have spent a little more time on this part.

chipenter · « **Reply #7 on:** June 04, 2017, 11:29:13 AM »

It's the same prosess as blueing , I have always done it straight from the polishing just don't tutch it with bear hands , I have mesed up a few clock parts with just one toutch .

velocette · « **Reply #8 on:** June 04, 2017, 12:39:47 PM »

Hi
The method I have been using is to heat until red hot and drop into used diesel engine oil (lots of carbon)
Be aware that the clouds of oil vapour are able to ignited from the red hot metal or any naked flame in the vicinity of the job
This becomes critical if doing a long run of parts and the oil gets very hot so be prepared for fire fighting

Eric

shipto · « **Reply #9 on:** June 04, 2017, 04:02:22 PM »

I guess time will tell but I didnt heat until red hot but my home built electric furnace lets me set the temperature to whatever I want within reason I may up the temperature a little the next time and clean the part more thoroughly. It would be nice to get a formula I know for certain is going to give me good results rather than good enough.
I think blowing the excess oil off the piece helped a lot, I didnt do it with the first few bits and it seemed to me that where the oil pooled it formed a crust which stopped the metal under it from turning and the two top rings I actually cleaned off and redid.

PekkaNF · « **Reply #10 on:** June 04, 2017, 05:06:02 PM »

Interesting...least three diferent prcesses are described here all having only one common nominator: Black.

I think that original method here that is imitated is japaning or japan black or it's variation.
https://en.wikipedia.org/wiki/Japan_black

Most typical use for me is the "black" on old Stanley plane inner parts.
http://www.inthewoodshop.com/ToolRestorations/ColdCureJapanning.html

BUT this does not work well on working surfaces. I would try to phosphate them. Personally I like tha metal gery sheen I get with vinegar or phosphorous acid. + oil.

Blackening/bluing with caustic near 160C temperature liquid is another process.

Then there are some cold bluing processes they produce pretty clean thin surface, but they don't seem to be as durable as original blueing.

Pekka

PK · « **Reply #11 on:** June 04, 2017, 06:16:38 PM »

None of these process' compare to the nitrate black you get on things like good machine tooling. Sadly, the chemical brew you need for that is nasty, even by my standards...
Parkorising (phosphate coating) isn't bad or hard to do and is commonly used on guns. Higher concentrations of phosphoric acid are tricky get in my part of the world though..

Biggles · « **Reply #12 on:** June 11, 2017, 02:09:13 AM »

Take a look at this video.

. i think that Brownels sell chemicals for blueing and Parkerizing.

AdeV · « **Reply #13 on:** June 11, 2017, 06:31:33 AM »

Interesting writeup here: https://www.milsurps.com/showthread.php?t=43247

The guy in the link used a regular battery to get his manganese (and some zinc, which would explain his grey-ish result). Concentrated phosphoric acid is easy to obtain in the UK - just look on eBay, or buy direct from one of the companies. I presume Manganese Dioxide is also easy to get although I've never tried.

PK · « **Reply #14 on:** June 11, 2017, 05:45:46 PM »

OK, gotta try that.
Thanks for posting

PekkaNF · « **Reply #15 on:** June 12, 2017, 01:36:20 AM »

There is a previous thread on homebrewed park
http://madmodder.net/index.php/topic,8995.msg100238.html#msg100238

I bough manganese dioxide from a pottery supply store, pretty economical stuff.

it's hard to get consistent with homebrewed mixtures and not all of the scrabnioum iron ore metals take the finish equally well.

Pekka

tom osselton · « **Reply #16 on:** June 12, 2017, 05:24:00 PM »

Quote from: PekkaNF on June 12, 2017, 01:36:20 AM

There is a previous thread on homebrewed park
http://madmodder.net/index.php/topic,8995.msg100238.html#msg100238

I bough manganese dioxide from a pottery supply store, pretty economical stuff.

it's hard to get consistent with homebrewed mixtures and not all of the scrabnioum iron ore metals take the finish equally well.

Pekka

In the link he says " Now you are ready to start the Parkerising process, pour the mixture in a stainless steel pot or pan of suitable size, obviously an old one that is not going to be used for cooking again, put a small piece of steel wool (about the size of a marble) in the mixture and bring it to boiling point. "
Why would the steel wool be needed?

awemawson · « **Reply #17 on:** June 12, 2017, 05:32:38 PM »

From what I've read elsewhere it seems to 'kickstart' the chemical reaction to get the brew working in the first place

PekkaNF · « **Reply #18 on:** June 13, 2017, 03:04:33 AM »

Yup, if you don't "bait" it with wire wool it will etch couple of first batch and then starts parkerizing. Note also that pretty much all of the wire wool you buy is rustproofed with oil....oil is best to be removed or it will not work.

My experience is that you need somewhat more than on that instruction....I found somewhere grams and when I weighted the amount of dry wire wool, it was a good tuft, more of a "hand" than a pinch

for a two litres of park. In industrial setup on old times the amount of chemicals were pretty small, but temperature was pretty well controlled, whereas on the majority of the writeups temprerature was described from simmering to rolling boil, worst case nearly 30 degree variation, which seems way too random for this process.

Pekka

redshift · « **Reply #19 on:** June 13, 2017, 04:58:30 AM »

It just so happens that I kept the example that was pictured in the Oct. 2013 thread as mentioned in Tom Ossleton's post ^^ up here.
It has been kicking around my workshop for the past few years, during this time it has only been oiled (WD 40) once.
I don't think it's done too bad as most steel in my place manages to develop surface rust in a matter of a few weeks. If it had been oiled on a fairly regular basis I'm sure it would still be as good as new.
The second pic is the fresh item and the following are as it is now.
Regards, Dave

seadog · « **Reply #20 on:** June 13, 2017, 06:24:40 AM »

Reading this brought to mind a set of darts that were Parkerised courtesy of The Royal Small Arms Factory Enfield in the mid 1980s.

The barrel material is tungsten carbide.

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Author Topic: Blackening (Read 23249 times)