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Friday, January 29, 2010

How to "Age" Brass and Copper

A DS original piece created using multiple brass patina and rusting techniques.

In this article, I have summarized some of the more traditional and simple methods of how to give brass (or copper) a vintage-looking patina.  I will use brass as the exemplar metal in the instructions, but most of these techniques will also work on copper.

     There are a couple of basic steps which always apply.

     First of all, make sure that your item is actually brass.  Most aging methods depend on the chemical reaction between the brass metal molecules and the reagent used.  (Introducing a different metal may be dangerous, or at best will not have the desired effect and be a waste of time and materials.)  You can find out by asking an antiques dealer, if needed.

     Second, remove any varnish, oil, or lacquer from the piece, as varnish can be chemically volatile and if your piece has any sealer on it, it will not change color!  Apply acetone, then submerge the piece in boiling water for a short period of time, wipe with a cloth until it seems all of the varnish has been removed, and let dry. (For larger items, apply the acetone, then rub the piece with very hot water on a cloth.)  Alternatively,  sand blasting will also effectively remove any coating on your brass.

     Third, please gather and wear personal protection -- goggles or other protective eye wear and latex/nitrile gloves.  Safety first!

     You will want to keep track of the time it takes for your piece to develop, in case you want to repeat the process someday.

     Now you should be ready to go!  But what method is best to use?  Good question.  Here are a few tried-and-true methods which use easily obtained and economical materials, and some harsher (but quicker) methods.

Salt Water and/or Vinegar

     Use a small brush to "paint" vinegar or a strong salt water solution (1 to 2 tablespoons or more salt per cup of water) on the surface which you desire to age. Let the piece air dry and repeat the process as many times as it takes to get the desired effect.  You also may try immersing your piece in the salt water or vinegar solution and letting it soak.   Cider vinegar or white vinegar will work; commercial-strength ammonia is not necessary but will also do the job.

     Many have suggested that a combination of vinegar and a good measure of salt (a couple of tablespoons per cup vinegar) speeds up the process and gives a more uniform finish.

     Using heat with vinegar gives a rapid result.

To get a "natural" aged brown brass finish with vinegar and heat:
  1.  Pour some vinegar into a plastic container and add a tablespoon or two of salt. 
  2. Mix well.  
  3. Put your pieces in mixture and let them soak for at least a few minutes.
  4. Remove the pieces and dry with paper towel.
  5. Place them on a cookie sheet and put them into a 450 degree oven.
  6. Monitor the change, which should occur in a few minutes.  
  7. Remove the pieces and let cool. 
To get a verdigris (green) patina: 
  1. Soak your pieces in the solution for 1 hour.
  2. Place them on a dark non-greased baking sheet and into a 450 degree oven for 20 minutes.
  3. Take the the hot brass pieces from the oven and place them into the vinegar solution. 
  4. Remove them from the solution in a few minutes or when the desired patina has been achieved. 
  5. Shake them off, carefully! Let air dry.
  6. Use very fine steel wool to polish and create highlights as desired.
Ammonia Vapor

     One of the most cited methods for aging brass involves the vapor of ammonia.
For small items, such as jewelry, you may put an ammonia-soaked wad of cotton or cloth in the bottom of a mason jar, then suspend the piece inside the jar lid and seal it up.  The brass should change within 30 minutes.  
  1. For larger pieces, select a container (with a lid) that will hold your item.  
  2. Place a smaller container (preferably glass) inside the bottom of your large container, and fill the smaller container with ammonia.  
  3. Place the brass in the large container so it does not touch the ammonia (liquid ammonia will form spots on the brass).
  4. Seal it tightly.  
  5. Monitor the piece daily and change the liquid ammonia solution every day to maintain potency; if you are environmentally inclined, you can neutralize the used ammonia with baking soda and water before disposing of it.
  6. Remove the brass when you are happy with the finish.
Chemical Methods

-- A mix of Miracle Gro, water and Novacan black patina solution from a stained glass supply can provide a fabulous and quick patina.
-- JAX patina chemicals work amazingly well, and quickly.   These are toxic chemicals, though, so you must read and follow the directions carefully.
-- Liver of sulphur -- add a pinch to warm water.    Degrease and heat the brass, then dip in this solution until you get the look you want.   This is not as toxic as   the two above.
-- Arcrylic Paints and Paint Pens can give you amazing results with some experimentation.  --To enhance the appearance of the piece, you might try products like Rub and Buff, or Renaissance Wax to add some definition to high or low spots.

Natural Methods (linseed oil, time, and...) 

     Don't like using chemicals?  Then you might try one of these methods.

      One is to heat your brass piece in the oven, and then immediately immerse the piece in linseed oil until you see the patina you desire (then remove and wipe dry).  

     The next option involves a leap of ... faith.  And a strong stomach.  Urine contains ammonia. Ruminants (grazing animals) have the highest concentrations of ammonia in their urine due to their plant-based diet.  This method is not very sanitary, of course, and is only mentioned for the sake of thoroughness.
     Soaking in the fluid is one method. (Collecting it is up to the artist!)  You may also try burying the brass piece in a dung/stall scraping pile or even in the kitty litter box for a couple of days (for those of us who are short on livestock).  
     In either case, wash  or sanitize your hands afterward, monitor the item over time and wash it well after it has attained the proper shade of antiquing from using this method. (!)
     If none of those natural methods suit you, then you may try rubbing your brass piece with your hands (the oilier the better), and then letting it sit in a location with good air circulation.  A natural patina will form over time (days or weeks).
     Other brass aging methods which also have their proponents include using a generous coating of yogurt, lemon juice, lye (gives a purple, green and dark brown patina), or even gun bluing.

     Whatever method you decide to try, after the brass has the patina you want and has dried thoroughly, a coat or two of varnish or matte lacquer sealant will help maintain the color you worked so hard to achieve.  Otherwise, the patina will continue to develop as the brass is exposed to oxygen in the air.  Remember to seal the front and the back of the piece.

A footnote from a recent experience -- I was using white wine vinegar and salt on a couple of pieces of what I thought was copper; that particular vinegar changed the metal to a green finish within mere minutes.  If I had rinsed the piece when it had reached the desired color, it would have been fine, but after several hours the metal had changed to many odd colors including pink.  I could speculate about the actual metal content of the piece, but on a separate try, I then discovered how to to stop the process and keep the finish.

Sprinkle dry baking soda on it, rinse it carefully, then pat it dry without wiping; this stops the development and once the metal dries, you will still have a nice verdigris on the metal (at least I did) and the acidity will be neutralized.

Enjoy antiquing your metal!

p.s. - If you want your brass to be a very specific color, check out this scientific site which lists everything you need to do just that: Science Company Patina Formulas for Brass, Bronze, and Copper.


  1. Very helpful and informative, and I love that you give a range of methods. I'm guessing my cheap brass bolts are just brass-plated, but I'm going to try some of the gentler methods anyway. The raw newness of the brass just doesn't looks steampunky enough for the room.

  2. I hope that one of the methods I described works for you. I am not sure how brass-plated objects will respond, but they should be fine with the "gentler" methods, as you mentioned. Best of luck with those bolts!



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