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Oppi Untracht Pickle Recipes Questions

Hey there everyone,

Been digging around for a good high production pickle solution for our workshop. We work in brass so we encounter the “copper blush” that comes with soldering and pickling brass pieces. Some time back I was recommended to use a normal pickle, we use acetic acid and salt, followed by a form of “bright dip” to remove the cuprous oxide using a diluted nitric acid bath. While this does work, I have to have nitric acid in our workshop which I would prefer not to have around if possible. We currently use all appropriate safety precautions, but still, better to not need it.

I was reading through Oppis Untracht’s Jewelry Concepts + Technology, and came across the following recipe:

1 part Sulphuric Acid
9 parts water
Used between 125-150 F

Then it says, when removing red cuprous oxide, add 4-8 ounces of sodium dichromate per gallon of above pickle.

Some questions about this recipe:

  1. What health hazards does having a warm crock pot of dilute sulphuric acid pose? Should I be concerned about any vapors being released, or is a crock pot on low next to an open window with a lid on it sufficient for any vapors that would be potentially released?

  2. Same question about health concerns, but in regards to the sodium dichromate added to the pickle.

  3. I know some have recommended a pickle made of Sparex (or acetic acid) and hydrogen peroxide which acts as an oxidizer to remove the red cuprous oxide, which we have used and it does work, but the short lifespan of the hydrogen peroxide mixture isn’t ideal for our scale of work, about 50 to 80 pieces per day. Will the sodium dichromate do the same job as the hydrogen peroxide, but with a more stable lifespan?

  4. Will the sulphuric acid, water, and sodium dichromate mixture be useful as a one stop pickle to remove the black cupric oxide and the red cuprous oxide all in the same go?

Thanks for any light you guys can shed on this!

The option of adding hydrogen peroxide to regular pickle does work well. We neutralized the pieces in white vinegar. It really strips away metal and exposes the granular structure of the metal, which is kind of cool, but not ideal for most finishes.

We usually added a 1/4c of hydrogen peroxide to a few cups of pickle. It has a short shelf life as does an open bottle of hydrogen peroxide and that is a problem, we often just refreshed the solution with more hydrogen peroxide. It was always such a challenge getting chemicals on campus, that was the go to so I never tried anything for a longer shelf life.

I wonder if adding anything like that to a citric acid pickle would be more stable. We need a chemist because it’s been too long since a did a chemical formula equation. I’ll be curious to see if other things work.

Ruthanne

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I pickle with Sparex then I put in peroxide/vinegar 50/50 to come back to brass. But like stated it does not last very long. I am curious for a better way also. I don’t mass produce but I work with brass a lot in my jewelry.

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:wink: [quote=“yewomalawi, post:1, topic:63229, full:true”]
Hey there everyone,

Been digging around for a good high production pickle solution for our workshop. We work in brass so we encounter the “copper blush” that comes with soldering and pickling brass pieces. Some time back I was recommended to use a normal pickle, we use acetic acid and salt, followed by a form of “bright dip” to remove the cuprous oxide using a diluted nitric acid bath. While this does work, I have to have nitric acid in our workshop which I would prefer not to have around if possible. We currently use all appropriate safety precautions, but still, better to not need it.

I was reading through Oppis Untracht’s Jewelry Concepts + Technology, and came across the following recipe:

1 part Sulphuric Acid
9 parts water
Used between 125-150 F

Then it says, when removing red cuprous oxide, add 4-8 ounces of sodium dichromate per gallon of above pickle.

Some questions about this recipe:

  1. What health hazards does having a warm crock pot of dilute sulphuric acid pose? Should I be concerned about any vapors being released, or is a crock pot on low next to an open window with a lid on it sufficient for any vapors that would be potentially released?

  2. Same question about health concerns, but in regards to the sodium dichromate added to the pickle.

  3. I know some have recommended a pickle made of Sparex (or acetic acid) and hydrogen peroxide which acts as an oxidizer to remove the red cuprous oxide, which we have used and it does work, but the short lifespan of the hydrogen peroxide mixture isn’t ideal for our scale of work, about 50 to 80 pieces per day. Will the sodium dichromate do the same job as the hydrogen peroxide, but with a more stable lifespan?

  4. Will the sulphuric acid, water, and sodium dichromate mixture be useful as a one stop pickle to remove the black cupric oxide and the red cuprous oxide all in the same go?

Thanks for any light you guys can shed on this!
[/quote]

1 Like