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For those of you who have had hit or miss success with blackening I have found the following techniques to work consistently and create a durable finish that won't rub or flake off. Most of the products are available from Beaducation, a jewelry supply store that also has great learning videos https://www.beaducation.com/pc/393-jewelry-making-tools-soldering-fusing-tools. Check it out.

 

The change I have made is that I now use Sparex on all my brass parts prior to blackening. Anyone doing silver soldering should have Sparex and a small pickle pot in their arsenal (see above link). The heated pickling solution removes oxide (and solder remnants) from the surface of the brass. I used to just soak the piece in acetone or alcohol to degrease but had some failures. Not so with the Sparex. These are my steps:

 

Pickle for 10-15 minutes. You must use copper tongs! I just keep my solution covered when not in use and it lasts for months. Do not forget to unplug or you will need a new crock  pot (ask me how I know)! It does not have an on-off switch.

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Place the brass items into a baking solution/water bath for a few minutes to neutralize the solution. If you fail to do this you will get uneven blackening (ask me how I know (again)!

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This is how they look after pickling. Clean as a baby's bottom.

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Place the brass objects in an acetone solution for ten minutes or so. I have also used isopropyl but acetone seems to work better for me. Keep covered and don't inhale the acetone! Use only disposable gloves to handle the objects from this point on. Any grease from your fingers will prevent the blackening solution from adhering.

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Prepare the blackening solution. I use hot water and Jax Blacken it. I use somewhere around a 1:7 ratio but in truth I just eyeball it. Place the brass objects into the solution and gently agitate so all surfaces are exposed.

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After 3-4 minutes rinse flush out the solution with warm water for a couple of minutes until it is clear. I do not reuse the blackening solution as it is inexpensive and seems to lose its potency after mixing. Dump the brass objects on a paper towel and gently blot dry. There will be an uneven powdery surface but this is normal. Allow to dry for 10-15 minutes.

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Use an eyeglass cleaner or old tee shirt to gently remove the surface covering then continue to rub. An evenly blackened surface should appear. You can also use a cloth polishing wheel at low speed to get into the nooks and crannies.

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And here's the final product. No streaks, blemishes or chips. I hope you find this useful. Next up, if interested, is how I conquered silver soldering (finally).

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Greg:

I have used the same technique and steps for several years - except I use Birchwood Casey Brass Black - and the heated Sparex is a world changer.  One place to get the little croc pots cheaply is the local Goodwill or similar store.  They always seem to have one or more for $3-$5.  I have 2 spares on hand in case the current one burns out.

Kurt

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Good Evening Greg;

 

Thanks for the advice, especially the 'what not to do' bits. Not sure if it's the picture, but the polished guns look a bit more bronze than black. Maybe just cleaning with a cloth leaves them blacker, perhaps.

 

All the best,

 

Mark P

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It's the lighting Mark. They are black. One could leave them in the blackening solution for a longer length of time to deepen the color. In that case I'd recommend a more dilute solution over a longer period of time.

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Thanks Greg, for the answer. I will give this a try with my next batch.

 

All the best,

 

Mark P

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Thanks Greg, very impressive.

The Sparex seems to be an important part of the success and I can't find a UK source (yet) for that product. However, it turns out Sparex is sodium metabisulphate: the stuff sold under the brand-name 'PH Minus' which is added to the swill in a hot-tub is the same material and is used by jewellers as a pickle. It is available from several suppliers.

HTH

Bruce

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Greg,

I have successfully used Sparex as well for a number of years but without heat which I will try going down the road.   Definitely a better way to go than acetone or other solvents that I had tried prior to using the Sparex.  Do you have any idea what temperature the crock pot gives you?    I was thinking it might be as easy to heat some water, dissolve the Sparex and put the pieces in the solution.   

Thanks for the description,  very well done and extremely useful.  

Allan

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It's my understanding that Sparex is only effective when it is very hot solution. I'm sure any jeweler in the UK would have pickling solution.

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Posted (edited)

A small hot plate that keeps your coffee hot works just as well for Sparex. Just don't absent-mindedly take a sip!

Edited by druxey

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5 minutes ago, dvm27 said:

I'm sure any jeweler in the UK would have pickling solution.

Oh yes, several specialist items available but this PH Minus product is cheaper, available off the shelf (in some places) and works. I found it was sold in sizes from 100g upwards as well so that is useful. I have used a model railroaders blackening product from CARRS MODELLING PRODUCTS in the past will get some of this PH Minus before long for comparison, will let everyone know what happens.

Has anyone here already used it and can comment?

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It is important that the Sparex doesn't boil (can't remember the exact hazard that results) but the crock pot can't get hot enough to boil the liquid.  So any heat source that doesn't boil it is OK.  The crock pot is perfect because it's got no metal - remember Greg's warning about using copper tongs - Sparex can't be stored or used in a metal container.

Kurt

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Posted (edited)

What is an optimum temperature for the this acid bath?

 

...I just googled it and found answer on Amazon. Here is an a question and answer from the seller:

 

 

Question:
 
 
 
Answer:
Sparex is generally added to luke warm water. It should not be heated over 125°F.
Thank you!

By PMC Supplies LLC Seller on August 29, 2017
 

 

Edited by Y.T.

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I use a glass container - actually a jam jar for Sparex. Leave the lid loose while heating though!

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I recently pickup this pickling chemical from a local jewelry supplier.

 

Pro-Craft Pickling compound (No. 45.122):  Sodium Bisulfate.   10 oz bottle makes 1 quart.   Solution works well at room temperature, but faster at about 125 F.

 

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