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Osmosis

My First Attempt At Metal Blackening

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I am currently building the Naval Smooth Bore Gun Kit from Model Expo. There are quite a few cast Britannia/Pewter I will also be using common BBs for round shot all of which will require blackening. After doing a search of this site specifically and the webs in general I decided to experiment on my own using mostly household products.

 

A little background. I have been in the Marine Water and Waste Water business for going on thirty years. My current job is designing Reverse Osmosis Desalination Systems. As such I have a fairly decent lab at my disposal. Not a lab in the strictly chemistry sense but also in the system testing and refurbishing sense. Lots of exotic cleaning chemicals and such. Any way I have a fairly good handle on water chemistry as it relates to the marine/seawater environment.

 

So Last night I started with a very concentrated Ammonia solution and heated it in the microwave for 30 seconds. Caution do not breath the fumes when removing from the microwave and if take it immediately to a well ventilated area preferably out side. I then dropped in a handful of BBs and one of the cast pieces I did not intend to use (see my build thread). After 15 minutes or so I noticed no change in the pewter and a slight discoloration of some of the BBs. I let them sit in the solution over night and everything looked the same when I got up.

 

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Notice the uneven coloration then compare it to the picture below.

 

I took the cast piece and one of the discolored BBs and one of the seemingly unaffected BBs to work with me for further testing. In the lab we use a product called Marikate On and Off Bottom Cleaner. It is a 30% Hydrochloric Acid, 10% Phosphoric Acid and water solution available in most all marine/sporting goods stores and most hardware stores. A weaker version called Aluma-Prep is what we use to etch aluminum prior to painting and an even weaker version is under you bathroom sink right now disguised as toilet bowl cleaner.

 

Anyway I put the parts in an undiluted batch of Marikate and immediately saw the blackening process begin and after 5 minutes and a thorough rinse with cold water had the results you can see below.

 

20171201_180820.thumb.jpg.51937fce139588c67dcb9a6678141c43.jpg

The scratches you see are me testing the hardness of the finish. I had to rub fairly hard with another piece of metal to scratch it.

20171201_180832.thumb.jpg.0b5d137fd2663a6fa636fbc81019df1c.jpg

 

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The Marikate evened out the finish on both BBs. I am still stumped on why only some were affected at all.

 

Tomorrow I am going to experiment on some brass using the same methods.

 

Thanks for looking in I hope this helps.

 

 

 

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Hello Art,

I just ran across this informative post, many thanks.

I'm a fan for using toilet bowl cleaners for other heavy duty cleansing issues, I'll surely add brass blackening to the list.

For other uses, the stuff will eliminate all plaque and other deposits from removable dentures, with no harm to the base appliance.

One can spend lots of time and cash for a thorough cleaning of dentures....or use toilet bowl and pipe cleaner as a remedy.

Fact, this is no BS.  I know a thing or two about teeth, not to worry.  Now, say aahhh...

Michael

 

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Thanks Michael,

 

I did not get very good results using this method on brass. But it works great on the cast white metal parts.

 

Regards

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I suspect that the problem with the BB’s is due to their composition. BB’s are usually made of steel, not Brass. They have a coating thick is probably brass, but if it has been compromised on some of them, the underlying steel may interfere with the blackening process.

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Thanks Vince,

 

I later discovered that they are plated with copper. I wound up using Perma Blue gun bluing solution and they came out pretty nice. I went into a little more detail in my build log.

 

Regards

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one method I use for blackening iron sword guards is to apply shoe polish then put over a gas ring. I am lucky enough to work in a forge part time, so can use that for larger objects, but  would think the best bet would be to use gun blue as a base and work from that?

 

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On 3/4/2018 at 5:48 AM, Osmosis said:

Thanks Vince,

 

I later discovered that they are plated with copper. I wound up using Perma Blue gun bluing solution and they came out pretty nice. I went into a little more detail in my build log.

 

Regards

For copper, use liver of sulphur.   EdT, uses it extensively on his clipper scratch build.

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For copper, use liver of sulphur.

I saw that on one of my google searches but could not find it locally.

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1 hour ago, Osmosis said:

I saw that on one of my google searches but could not find it locally.

Hi Art

 

Perhaps try jewellery supply houses, I've also seen it at a casting/molding supply for theatrical props, masks etc.

 

Mark

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Posted (edited)

Not sure if you are set on the b.b's or not but could you use ball bearings? They would be easier i think since you could just use an etching solution or salt water and elecric current (wich i fimd to work well when etching steel).

  Auggie

Edited by mmd373
To add to my post

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