Wednesday, July 22, 2009

Patinating Copper Experiments

I've been plugging away on the reproductions for Parks and working on one last wholesale order this week. Its not a huge wholesale order, but I have almost no product on hand so I'm pretty much starting from scratch on it.

Here's an update on the copper patina experiments. I've been testing different combinations of Red Wine Vinegar, Sea Salt, Miracle Gro and water on heavy copper ground wire. The vinegar and salt combinations tend to give a nice green patina although the crystals grow fairly large on the surface. They can be brushed off fairly easily, but I'd prefer if they didn't grow so big in the first place. I start with a tablespoon or so of vinegar and stir in as much salt as the solution will hold, a teaspoon or more. I've read that the more salt in the solution, the more green the patina will be and also that Red Wine Vinegar is the prefered vinegar to use.

Miracle Gro brings ammonia into the mix, which also reacts with copper to produce a patina, although it creates a more bluish colour. Miracle Gro mixed with water creates a nice blue patina. I don't think its a good match for the artifact I'm trying to reproduce, but its an interesting look. Personally, I'm happiest with the Red Wine Vinegar and Miracle Gro solution. I mixed the solid miracle gro pellets into a tablespoon of vinegar, the same way I did with the salt. The resulting patina is a blue-green mix, but without the heavy crystal growth. It creates a nice dusty patina.

I also tried lightly sprinkling the copper with the mixture and completely submerging it in the salt and vinegar mix. The light sprinkling was definately the better way to go. By the time the vinnegar all evaporated, the salt crystals that grew on the submerged copper were huge (photo to the left). Not much use to me.

When I visit the artifacts at The Rooms tomorrow, I'll take my samples with me and see which treatment gives the closest match to the patina on the copper awl.

One final note, the green crystals that form on the copper and the plate are called verdigris. Its one of the original sources of green pigment used in painting. I'll save it and use it on another reproduction. There is a bent wood piece that I think may be a kayak rib with some green staining on it. The verdigris will be a good colour match for that stain on the reproduction.

(Above) Red Wine Vinegar and Sea Salt Patina on Copper after 5 days. Most of the growth happened within the first 24 hours. Note the big crystals.

(Above) Miracle Gro and water patina growth on copper. 3 Days growth. Decent growth, but I think its going to be too blue.

(Above) Miracle Gro and Red Wine Vinegar patina on copper after 3 days. This is the recipe that I'm pulling for. I have to do a side by side comparison with the artifact, but the colour and crystal size all look pretty good to me.

Photo Credits: Tim Rast

Photo Captions:
Top: Raw copper wire used in the experiments
Second: Photo of Ingredients and trays with on-going experiments
Third-Six: Results photos.


  1. Fascinating post. I'm going to add myself as a follower so I don't miss stuff like this one.

  2. Thanks Carol, I hope there'll be lots more posts like this with experiments and antiquing recipes. A lot of my work is trial and error and I don't have the memory to recall all this stuff if I don't write it down somewhere.

  3. Great information. I've been experimenting too and find your experiments interesting. I've been playing around with heat and copper...namely the sun and I've gotten some beautiful colors, too!

    Thanks for the information about the Miracle Gro. I use ammonia and pine shavings...interesting results. Same with vinegar.

  4. Hey JFisher - have you found that the sunlight gives you a cloudy white colour over the patina? It seems like I get more of the whitish clouds on the copper when the solution evaporates quicker, ie. in the sun or on less humid days.

  5. Hey Tim. Great piece. very Alice the Alchemist. I believe the recipe for 'verdigris' which is malachite right? or something medieval painters would pound into powder for green paint. I read that they would suspend copper ribbons in a wooden box inside a dung heap. They would leave it all winter, and the ribbons would be so corroded they'd crumble but you prolly dont want that, nor do you likely have a dung heap full horse manure handy...

  6. Very interesting. I experimented unsuccessfully with this, but perhaps it was because I used the liquid version of miracle grow. Also, I am unclear as the ratio between miracle grow and red wine/salt blend. Could you please clarify?


  7. Hi Arnold, when I added the sea salt and the miracle gro to the vinegar I stirred it in slowly and it dissolved into the liquid. When it stopped dissolving and started settling out I stopped adding salt/miracle gro. I didn't really measure how much I was adding - I used pretty much the maximum amount of salt or miracle gro that would disolve in the vinegar. The reproductions I was working on were very small, so the amounts were approximately 1 tsp of salt/miracle gro for a tablespoon of vinegar.

  8. Thanks Tim! Actually, my first experiments actually ended up working out a bit better than I first thought. Once I removed the wire from the solution they developed a better patina a day or two later. Not like your results but improved. I'll do another run at it using your suggestions.

    Just to clarify, is the resulting solution you mix up quite fluid or somewhat thick and pasty?

  9. The mixture is still very fluid -- it doesn't look or act much different than vinegar without salt in it. And yes, I had the same experience as you - the reaction needs air. I had the best results with a light sprinkling of solution and exposure to air. The submerged copper wouldn't patinate until the solution evaporated and exposed it.

  10. Any ideas on restoring patina on shield granite that has been pressure washed in error?

  11. About how many Miracle Grow pellets did you mix with the 1 tbsp Red Wine Vinegar?

  12. It was about a teaspoon of miracle gro for every tablespoon of vinegar.

  13. Try thoroughly cleaning the copper first in a ultrasonic cleaner with a good solvent used for cleaning old technical drafting pens. We used to throw pennies in the cleaner at work before the advent of computers and after a night of cleaning when dry they would turn green very quickly without anything else put on them. The ultrasonic gets them so clean that the atmosphere can do its thing immediately.

  14. I've been experimenting with patinating copper with vinegar and salt but I do it in a plastic container (an old curry container from Tesco) with Salt and Vinegar crisps.
    The crisps are crunched up, sprinkled into the container and sprayed with a misting of water, then I lay the copper pieces on top and then add another layer of crisps, spray with water again - I press the copper onto the crisps a little to ensure decent contact with the crisp pieces - this is because the pieces of crisp actually help create the pattern of patination. Spray top layer of crisps with water too - and I usually add a dash or so of balsamic vinegar as well.
    For this I use copper sheet that was gifted to me by a friend, it's fairly stiff but just cuttable with ordinary scissors. Some people use very thin copper sheets which are a bit stiffer than kitchen foil - and that stuff usually has a coating, for that you need to first soak the copper in fresh boiled water with a couple of handfuls of salt in it (while still hot) - some also sand the copper before using crisps.
    photos of the resultant patterns of patination are here:
    and here:
    Here are my first attempts with heat:

    Fran B.

  15. Fran: Thanks for the links and the Salt and Vinegar chip recipe. I like those results and I love S&V chips! I'll definitely give this a try next time around.

  16. Thanks for posting your tests - I'm now experimenting with your Miracle Gro recipe, I didn't have red wine vinegar at the time (but went and bought some today! Lol!) so I used Malt Vinegar. I also had slow release Miracle Gro - does that matter do you think? I did have Maldon Sea salt though and I'm surprised at the different green this produces. I'll try and remember to pop a photo of this colouration on my website tomorrow.
    But it's not as dark as your image suggests it should be. Not so much bottle green as minty/emerald green.
    I must try the next batch with the red wine vinegar... and perhaps crushing the slow release Miracle Gro...

  17. A little word of caution. My father recently had a bad gas leak in his house caused by a box of miracle gro which had eaten a hole the size of a 50 p coin in the 22mm main gas pipe. lesson don't store the fertiliser next to copper pipes.

  18. Luckily my Miracle Gro is in a plastic container - with no holes. But just because we want corrosion in some places, doesn't mean we should forget how to store things properly. Good reminder, thanks.(I hope your father was okay)
    Here are the results of liquid puddling on a copper blank as it dried. It created the most beautiful pattern, like tree rings or maybe a fingerprint.
    I have 3 more blanks in this solution, which I may take out or leave for the vinegar to dry up natually... not sure yet.
    But I want to try some more but with the red wine vinegar this time.

  19. good for ornament work.....all surface change, though...have you found that, also......& also the people who wish to deceive for $$$ on fake copper artifacts are always about.

  20. I just found your site -- how do you preserve/fix the patina once you've "grown" it?

  21. hi! materials engineer here, you don't need all that salt to get the patina, just add a tea spoon for a cup of vinegar, you'll get the same effect and smaller cristal to brush off =) i'm also quite sure that you'd get the same effect addig HCl instead of table salt,the crucial ellement in this patinas is the Cl- ion, it's not important where it comes from. Chears!

  22. I have copper foil I'm trying to patina using miracle gro and water and tried miracle gro and vinegar. I cleaned copper with acetone first. I brushed on the solutions and the water just slides off and I don see anything happening in the first hour. What am I doing wrong??

  23. no responses to long ago questions...

    1. I guess I don't have all the answers.

  24. The surface probably wasn't rough enough for it to grab


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