Any Chemists Know What’s Going On Here?

I shaved using my Captain’s Choice heavy copper lather bowl this morning. The lacquer coating is worn off on the inside so it’s bare copper. I bowl lather and scoop soap and smear it onto the bowl. Today I used MDC original and smeared three strips of soap into the bowl. Yes, way too much but it’s not like I’m short soap. Anyway, MDC is harder than most modern soaps do there was still soap left smeared onto the bottom of the bowl after I’d produced excessive amounts of lather and I had to scrape it off with my thumbnail afterwards while rinsing the bowl out. The soap left a stain or oxidized marking on the copper. Does anyone know what’s going on? I’m assuming some chemical reaction but I’m curious to know specifics and if it’s anything to be concerned about. I haven’t noticed this phenomenon with other soaps that I’ve used.  It’s not a film or anything adhered to the surface

Interesting…..

I've seen the same sort of thing on my copper cookware, especially when I don't rinse and dry it well enough after washing it. Have you tried cleaning it up with a little copper polish or brass polish? That usually returns my copper to its pristine state.

I've also noticed that Martin de Candre soaps chew the finish off any wooden bowl. Nice soaps, but probably best kept in glass.

Copper is a fairly reactive metal. That it why it is frequently alloyed with zinc to form brass. Because the zinc it even more reactive than copper, it tends to lessen the corrosion of the copper. But brass tarnishes as well providing ample work for sailors who are given the task of polishing the brass. That is why copper and brass are typically coated with lacquer.

The blue coloration is either copper chloride or copper sulfate. Copper sulfate tends to be blue and copper chloride tends to be greenish blue. Since the color has some green, it is likely copper chloride. Copper chloride forms whenever bare copper is exposed to hydrochloric acid or to chlorine compounds such as bleach. Since tap water is usually disinfected with chlorine or chlorine dioxide, you have the necessary chlorine ions to form the chloride salt of copper.

Fortunately, removal of corrosion products from copper is not difficult. You can mix vinegar or lemon juice with table salt to make a paste that should clean it up. You might be able to relacquer the bowl to minimize the frequency of cleaning.

As @Oahu indicated, a commercial brass polish like Brasso will also do the job, but I do not like the smell. .

Copper is a fairly reactive metal. That it why it is frequently alloyed with zinc to form brass. Because the zinc it even more reactive than copper, it tends to lessen the corrosion of the copper. But brass tarnishes as well providing ample work for sailors who are given the task of polishing the brass. That is why copper and brass are typically coated with lacquer.

The blue coloration is either copper chloride or copper sulfate. Copper sulfate tends to be blue and copper chloride tends to be greenish blue. Since the color has some green, it is likely copper chloride. Copper chloride forms whenever bare copper is exposed to hydrochloric acid or to chlorine compounds such as bleach. Since tap water is usually disinfected with chlorine or chlorine dioxide, you have the necessary chlorine ions to form the chloride salt of copper.

Fortunately, removal of corrosion products from copper is not difficult. You can mix vinegar or lemon juice with table salt to make a paste that should clean it up.  You might be able to relacquer the bowl to minimize the frequency of cleaning.

As @Oahu indicated, a commercial brass polish like Brasso will also do the job, but I do not like the smell. .

Thanks for the information - I'll try to clean it with salt and lemon juice.  I think its reacting with something in the MDC soap because I use the bowl almost everyday and it doesn't do that with any of the other soaps I use.  I haven't used MDC in a long time.

Tell me more 

If I'm wrong show me, but I'll still prefer boar.

Here is what I posted last night but wanted to see if I can find out more. After posting this image, I wasn't sure if when Plisson started whether they used badger or boar bristle. I will send them a message on IG to see if they will share.

Copper is a fairly reactive metal. That it why it is frequently alloyed with zinc to form brass. Because the zinc it even more reactive than copper, it tends to lessen the corrosion of the copper. But brass tarnishes as well providing ample work for sailors who are given the task of polishing the brass. That is why copper and brass are typically coated with lacquer.

The blue coloration is either copper chloride or copper sulfate. Copper sulfate tends to be blue and copper chloride tends to be greenish blue. Since the color has some green, it is likely copper chloride. Copper chloride forms whenever bare copper is exposed to hydrochloric acid or to chlorine compounds such as bleach. Since tap water is usually disinfected with chlorine or chlorine dioxide, you have the necessary chlorine ions to form the chloride salt of copper.

Fortunately, removal of corrosion products from copper is not difficult. You can mix vinegar or lemon juice with table salt to make a paste that should clean it up.  You might be able to relacquer the bowl to minimize the frequency of cleaning.

As @Oahu indicated, a commercial brass polish like Brasso will also do the job, but I do not like the smell. .

Thanks for the information - I'll try to clean it with salt and lemon juice.  I think its reacting with something in the MDC soap because I use the bowl almost everyday and it doesn't do that with any of the other soaps I use.  I haven't used MDC in a long time.

Ketchup, yes ketchup, let it sit for a couple of minutes and wash it with soap and water. You'll be amazed.  

Tell me more 

If I'm wrong show me, but I'll still prefer boar.

Here is what I posted last night but wanted to see if I can find out more. After posting this image, I wasn't sure if when Plisson started whether they used badger or boar bristle. I will send them a message on IG to see if they will share.

Copper is a fairly reactive metal. That it why it is frequently alloyed with zinc to form brass. Because the zinc it even more reactive than copper, it tends to lessen the corrosion of the copper. But brass tarnishes as well providing ample work for sailors who are given the task of polishing the brass. That is why copper and brass are typically coated with lacquer.

The blue coloration is either copper chloride or copper sulfate. Copper sulfate tends to be blue and copper chloride tends to be greenish blue. Since the color has some green, it is likely copper chloride. Copper chloride forms whenever bare copper is exposed to hydrochloric acid or to chlorine compounds such as bleach. Since tap water is usually disinfected with chlorine or chlorine dioxide, you have the necessary chlorine ions to form the chloride salt of copper.

Fortunately, removal of corrosion products from copper is not difficult. You can mix vinegar or lemon juice with table salt to make a paste that should clean it up.  You might be able to relacquer the bowl to minimize the frequency of cleaning.

As @Oahu indicated, a commercial brass polish like Brasso will also do the job, but I do not like the smell. .

Thanks for the information - I'll try to clean it with salt and lemon juice.  I think its reacting with something in the MDC soap because I use the bowl almost everyday and it doesn't do that with any of the other soaps I use.  I haven't used MDC in a long time.

Ketchup, yes ketchup, let it sit for a couple of minutes and wash it with soap and water. You'll be amazed.  

The acid in the tomatoes?

I've had that happen in my copper captains choice bowl as well with certain soaps. I can't recall which ones though. I noticed it almost immediately after washing out the remainder of the soap.

If it's copper chloride, then it would get the chlorine from the sodium chloride in the MDC.

Here is what I posted last night but wanted to see if I can find out more. After posting this image, I wasn't sure if when Plisson started whether they used badger or boar bristle. I will send them a message on IG to see if they will share.

Thanks for the information - I'll try to clean it with salt and lemon juice.  I think its reacting with something in the MDC soap because I use the bowl almost everyday and it doesn't do that with any of the other soaps I use.  I haven't used MDC in a long time.

Ketchup, yes ketchup, let it sit for a couple of minutes and wash it with soap and water. You'll be amazed.  

The acid in the tomatoes?

Yep, try it on a penny and you will see