# Black Oxide Comparison



## Aliva (Sep 8, 2022)

Not really project but close.
I decide to do a test comparing 2 different black oxide treatments
I'll compare Brownells OxPho-Blue to Caswell Plating's cold black oxide concentrate.
Product:
Brownells Oxpho-Blue 4 oz. U.S. 
Cost from Amazon $34.54  $8.58/ U.S. oz. (taxes and shipping extra)

Caswell Plating Black Oxide concentrate 1 Pint imperial
Cost from Caswell $43.45  $ 2.17/ Imperial .oz  taxes and shipping extra)

The Brownells solution was used as recommended undiluted from the bottle.
The Caswell was used directly from the bottle and undiluted, Caswell recommends  dilution of 9 parts distilled water to 1 pint of concentrate.

The test pieces are  1/4" CRS freshly milled and cleaned with acetone, I divided the pieces in 1/2 with tape and numbered 1-4.
Pieces 1 and 2. The oxide solution was applied to each by rubbing in for 1 minute at an ambient temp of approx. 24C
Brownells  on section 1
Caswell on section 2

Test pieces 3-4 was applied after the pieces were heated to approx. 100F
Brownells on section 3
Caswell on section 4

Conclusion:
Piece 1 Brownells at ambient temp show blackening but some color hues showing up not a solid black. A lot of mottling
Piece 2 Caswell at ambient temp shows much better darkening and more uniform in colour.

Piece 3 Brownells at 100F shows better colour and even throughout.
Piece 4 Caswell at 100F shows similar to the Brownells in results.
NOTE. None of these pieces have been sealed with oil as per Casswell's  instructions, Brownells doesn't mention this in their instructions.

So Caswell shows a much better constant result for 1/4 of the price.


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## David_R8 (Sep 8, 2022)

Interesting results. For my likely very infrequent use I've always balked at the price of the chemicals.


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## gerritv (Sep 8, 2022)

Thank you for the confirming comparison. Glad I went wth Caswell.

I use Caswell at 9:1 or is it 1:9, at room temperature. I generally glass bead blast first, then acetone or isopropyl rinse. Always clean finger cots or gloves when handling at this stage. Before blackening on the left, after 3 minutes in the solution plus blow dry and oil. I am 20-25 parts in on the first mix of solution, no signs that I need to top it up. So a pint will last a very long time at this rate. I keep the solution in a 1l sealed top jar.


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## ducdon (Sep 8, 2022)

Are there any old school methods for blackening parts . Hot dip them in? I'm sure blacksmiths have been doing something like this for ever?


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## boilerhouse (Sep 8, 2022)

ducdon said:


> Are there any old school methods for blackening parts . Hot dip them in? I'm sure blacksmiths have been doing something like this for ever?



I restored an older wood working vise, and to make the new fasteners look more "period correct", I heated them up with a propane torch, then dipped them in a heavy oil.  The vice itself was heated the same way, and wiped with boiled linseed oil, but beware that this process gives off some nasty fumes, so take precautions accordingly.


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## David_R8 (Sep 8, 2022)

ducdon said:


> Are there any old school methods for blackening parts . Hot dip them in? I'm sure blacksmiths have been doing something like this for ever?


There is the rust bluing method as well.


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## Susquatch (Sep 9, 2022)

gerritv said:


> Thank you for the confirming comparison. Glad I went wth Caswell.



Hmmmm....... I smell much more than bluing salts buried in those photos you just posted! 

Please tell us more about what you are making there! And I see finished parts too! 

Have you used it yet? Any photos of how well it works? 

PS - Very nice photos! You & @thestelster must have gone to the same photography school.


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## Susquatch (Sep 9, 2022)

Aliva said:


> Not really project but close.



Yes it is. It's a full blown project in my eyes for sure. 

Very useful information that all of us can benefit from. 

Thank you for doing this.


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## trlvn (Sep 9, 2022)

David_R8 said:


> There is the rust bluing method as well.


I've tried this on some T-nuts but the results were nothing like the above picture.  The T-nuts have a mottled dark-red-rust appearance and the process does take some time.  Now that I have a bottle of Jax Blackening solution, I'm not planning to do any more rust bluing.

Here is another example of Jax Blackening:






These are the locking screws for my RF-30 mill.  I needed to make them longer to get past the DRO scale.

Craig


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## gerritv (Sep 9, 2022)

Yes, I have spent a lot of time photo-ing things. With a few short exceptions, always Pentax cameras. But in the recent few years just snaps using cell phone. At one time I was doing >500/day plus editing in LightRoom when on our long cruises.

I will start a new post on the cut knurler.


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## thestelster (Sep 9, 2022)

ducdon said:


> Are there any old school methods for blackening parts . Hot dip them in? I'm sure blacksmiths have been doing something like this for ever?


The chemical colouring of steel objects has been around since the 17th century, mostly used for armor or firearms.  I have a book which has 150 different formulae for blackening or browning gun parts using the traditional rust blue method.  

The formula that I use consists of hydrochloric acid, nitric acid, iron filings and distilled water.  It can take up to a week, applying the solution twice a day, to properly blue a pair of shotgun barrels.


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## Darren (Sep 9, 2022)

I've done several parts by heating to dull cherry with a torch, dunking in used diesel oil. Sometimes twice. The results have been great.


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## David_R8 (Sep 9, 2022)

trlvn said:


> I've tried this on some T-nuts but the results were nothing like the above picture.  The T-nuts have a mottled dark-red-rust appearance and the process does take some time.  Now that I have a bottle of Jax Blackening solution, I'm not planning to do any more rust bluing.
> 
> Here is another example of Jax Blackening:
> 
> ...


To be fair I have not tried rust bluing.


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## Tom O (Sep 9, 2022)

Here’s blackening some armour with linseed oil.


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