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Cleaning Copper

edited September 2013 in General

Got a new Alembic. what is the best way to clean the black crap out of the Lyne arm? Done a vinegar boil at around 3-1 water to 5% vinegar. I can still see black crap on the inside of the arm. Ideas?


  • Look into Sodium Sulfate (Pool PH Down) and Hydrogen Peroxide bath.

    The Sodium Sulfate will remove all the Black oxide off the copper but you will probably also have Red Oxides as well you will want to remove under the Black. The Hydrogen Peroxide will convert any Red Oxide to Black and then the Sodium Sulfate will remove all the Black.

    It is a 2 step process. Sodium Sulfate bath first to remove all the top level Black Oxide. Then add the Hydrogen Peroxide to the bath which will convert any Red Oxide that was under the Black before to now being Black so the Sodium Sulfate can remove it.

    It also will not hurt Stainless Steel so this is how I am planning to clean my new Copper and SS 8" Dephlag once I fix all the pin hole leaks.

    Read up on it before you use it as it is a fairly strong acid bath. Safety First!!! You will also need to do Neutralize bath on your piece afterwards to stop the process. (Baking Soda Water)

  • I have pounds of citric acid. hmmm......

  • @nvnovrts said: I have pounds of citric acid. hmmm......

    Less elbow grease!

    It is what you make it!

  • citric works very well.

  • I have quite a build up of scale around the edges of the plates inside the column, probably because of the quality of the water here, the kettle in the kitchen need de-scaling every month. I am planning to use citric acid, it works for the kettle so it should work for the still.


  • Just wondering, what is left in the boiler at the end of the run is both hot and usually acidic.

    How feasible would it be to pump some of it up to the top plate and back flush all the plates into the boiler before you drain it. Then to finish off just flush some clean water through it.

  • Sodium Sulphate is known as Glaubers Salts, it is slightly alkaline, and used as a laxative, are you sure ?

  • When I clean my plates and caps with citric, they don't come out very sparkly. Still dull. A toothbrush helps but not what I was expecting. I want my copper plates looking like bling!

  • edited September 2016

    The downside to heavy acid treatment, or even just manual polishing, and getting them super bright is that you are eating away the copper.

    You don't need sparkle.

  • I don't really use a heavy treatment. The problem is I remember what they looked like when I first got them.... :((

  • What about phosphoric acid?
    Wasn't there something about the patina on the inside of the still being more 'active' than bare, pink metal?
    It was actually beneficial to the spirit in some way, not to go back to raw metal?

  • Yes I remember reading that somewhere

  • I was told 4% Phosphoric acid

  • edited September 2016

    I use a dilute vinegar and salt solution that works very well.

    5L of Heinz cider vinegar, two pounds of Morton salt, mixed into enough water to fill a 50 quart cooler. An overnight soak does wonders.

    I'm more like I am now than I was before.

  • I have started adding smaller amounts of acid and measuring the PH, replenishing a little when the acid gets used up... (you do not even need to calibrate your PH meter, add a known amount, take a measurement, when it loses that acidity, add a bit more acid if needed...

    example, 5-Star Acid Cleaner # 5:


    I add just 7ml (1/4oz) in 5 gallons (about 1/20th the amount) and get about 3.5 or so.. (adding 1/10th would take it exactly 1 point higher)... if/when it gets back up to 5 or so, and I need I add another few ml if I need more cleaning power...

    FYI - I may start using coke or ketchup! (LOL)
    Copper Cleanup (PDF)

  • as a bonus, acid cleaner # 5 is designed to passivate your stainless... yes, it is $75/gal, but it will last you a lifetime

    Acid Cleaner # 5 (PDF)

  • just drain your backset in a bucket throw in your copper, clean as new for free

  • old thread but there's not enough science in this post ;)

    Paraphrasing from Why do citric acids clean pennies best @ and a few other sources

    We measure acidity on the pH scale, which tells us how much H+ has ionized into the solution. Basically, the lower the pH, the more acidic the solution is, and the more capable of attacking metals, rusts, and oxide tarnishes.

    An important quantity to know for weak acids is the acid dissociation constant K_a which lets you know to what extent the acid will ionize or give off H+ when dissolved in water.

    As far as the first K_a value goes for weak acids, Oxalic acid is the strongest, with Phosphoric acid, citric acid and malic acid following in order of strength respectively. What this all boils down to, is if you had solution of each acid all at the same concentration, the one with the highest K_a value would clean copper the fastest.

    For other acids, see Table of Acid and Base Strength

    Citric acid: C6H8O7, found in many types of fruit, is triprotic and can release up to 3H+ when dissolved into water. Being a weak acid however, you won't lose all three H+ unless you have a strong base present. It's acid dissociation constants are K_a1 = 7.4e-4, K_a2 = 1.7e-5 and Ka_3 = 4.0e-7.

    Ascorbic acid: C6H8O6, found in lemons and limes, is diprotic and can release up to 2H+ when dissolved into water. It?s acid dissociation constants are K_a1 = 8.0e-5 and K_a2 = 1.6e-12.

    Malic acid: C4H6O5, found in green apples, and is also diprotic. It?s acid dissociation constants are K_a1 = 4.0e-4 and K_a2 = 7.7e-6.

    Oxalic Acid: C2H2O4, found in rhubarb (a leafy red/green vegetable) and beets, is diprotic. It?s acid dissociation constants are K_a1 = 5.9e-2 and K_a2 = 6.4e-5.

    Acetic acid: C2H4O2, found in vinegar, is monoprotic and releases one H+ when dissolved into water. It's acid dissociation constant is K_a = 1.8e-5

    The copper metal (Cu) has reacted with oxygen in the air (O) to form copper oxide tarnishes like Cu2O. When you remove the tarnish from copper with an acid, the chemical reaction is something like: Acid + copper oxide => copper salt + water

    balancing the equation before proceeding: 2 acid + 1 copper oxide => 1 copper salt + 1 water

    Example with citric acid: 2 H+ [citrate anion]-- + Cu++ O-- => Cu++[citrate anion]-- + H20

    NOTE: Chloride salts such as NaCl may aid the dissolution of copper(II) oxide CuO by the high solubility of copper chloride CuCl2 over say copper(II) citrate Cu3(C6H5O7)2 (which is a much more complex structure)

    NOTE2: For weak acids, the more concentrated the solution the less the acid ionizes. So while pH does decrease for more concentrated solutions, it decreases more slowly as the concentration goes up. This implies that a super concentrated solution isn't terribly more effective at cleaning copper as a more dilute one. It also implies that solutions of two different acids at two different concentrations can give similar pHs. However, the speed at which one solution cleans over the other will dependent mostly on the K_a value for that acid. In conclusion, knowing the pH isn't enough information to decide if that solution will clean better (faster).

    • HCl, is muriatic (hydrochoric) acid
    • H2SO, is sulfuric acid
    • H3PO4, phosphoric acid
    • HNO3, nitric acid
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