A while back someone raised a question regarding the use of copper wire in a mash tun build I had posted. They were concerned over the possibility of developing verdigris poisoning by having hot wort come into contact with copper. We've all seen those copper roofs, drains and water lines with a green colored patina on them, the patina is formally known as verdigris. I've never known, or heard of anyone being poisoned by it, even though some sources say coming in contact with large amounts of verdigris can cause nausea and vomiting. The issue isn't with wort coming into contact with copper, that's perfectly fine, the potential for poisoning occurs when verdigris forms on the copper and it comes into contact with your wort. So to some extent the concern seemed to be valid, but I felt the level and causes for concern needed to be explained and understood too.
In my mash tun build I used a braided stainless steel filler connector for the grain filter. I reinforced the inside of the braid with a spiral made from 12 gauge copper wire, to prevent the braid from collapsing under the weight of the wet grain. So after two years of use, brewing at last once a month during that time, I decided to tear down the grain filter and inspect it. I knew that brewers have for centuries referred to their kettle as 'the copper' because kettles were in fact made from copper. I'm pretty sure if their kettles produced poisonous beer there wouldn't as many brewers or beer drinkers around as there are today. Eventually I did come across an article titled Metallurgy For Homebrewers in Brew Your Own Magazine, that explained away a lot of the myth surrounding verdigris and brewing.
"Copper is relatively inert to both wort and beer. With regular use, it will build up a stable oxide layer (dull copper color) that will protect it from any further interaction with the wort. Only minimal cleaning to remove surface grime, hop bits and wort protein is necessary. There is no need to clean copper shiny-bright after every use or before contact with your wort. It is better if the copper is allowed to form a dull copper finish with use." ~ John Palmer November 2007
Once I had the stainless steel braid and copper wire apart it was easy to see that there were no signs at all of any green colored verdigris patina on any of the surfaces. In fact I was relieved to see that the entire copper surface of the reinforcing wire had developed a nice dull copper oxide layer. As for maintaining my mash tun all I had been doing is flushing the grain out with water and then turning it upside down to air dry. I had read of other brewers using white vinegar and salt or StarSan to shine up their copper parts but after doing some research I was convinced this wasn't at all necessary.
After reassembling the grain filter I went on to use that same mash tun for another two years, in fact I eventually built a second mash tun using the same design and haven't had any issues with either of them. I produced some fine beers with those two over the years and even though I've since upgraded to a RIMS brewing setup, I still have them in my brew room. My advice to anyone currently using copper, or planning to include copper in their brewing process is to RDWHAHB and dispel all those verdigris myths.
Vince Feminella [aka: ScrewyBrewer]
www.thescrewybrewer.com
[email protected]
In my mash tun build I used a braided stainless steel filler connector for the grain filter. I reinforced the inside of the braid with a spiral made from 12 gauge copper wire, to prevent the braid from collapsing under the weight of the wet grain. So after two years of use, brewing at last once a month during that time, I decided to tear down the grain filter and inspect it. I knew that brewers have for centuries referred to their kettle as 'the copper' because kettles were in fact made from copper. I'm pretty sure if their kettles produced poisonous beer there wouldn't as many brewers or beer drinkers around as there are today. Eventually I did come across an article titled Metallurgy For Homebrewers in Brew Your Own Magazine, that explained away a lot of the myth surrounding verdigris and brewing.
"Copper is relatively inert to both wort and beer. With regular use, it will build up a stable oxide layer (dull copper color) that will protect it from any further interaction with the wort. Only minimal cleaning to remove surface grime, hop bits and wort protein is necessary. There is no need to clean copper shiny-bright after every use or before contact with your wort. It is better if the copper is allowed to form a dull copper finish with use." ~ John Palmer November 2007
Once I had the stainless steel braid and copper wire apart it was easy to see that there were no signs at all of any green colored verdigris patina on any of the surfaces. In fact I was relieved to see that the entire copper surface of the reinforcing wire had developed a nice dull copper oxide layer. As for maintaining my mash tun all I had been doing is flushing the grain out with water and then turning it upside down to air dry. I had read of other brewers using white vinegar and salt or StarSan to shine up their copper parts but after doing some research I was convinced this wasn't at all necessary.
After reassembling the grain filter I went on to use that same mash tun for another two years, in fact I eventually built a second mash tun using the same design and haven't had any issues with either of them. I produced some fine beers with those two over the years and even though I've since upgraded to a RIMS brewing setup, I still have them in my brew room. My advice to anyone currently using copper, or planning to include copper in their brewing process is to RDWHAHB and dispel all those verdigris myths.
Vince Feminella [aka: ScrewyBrewer]
www.thescrewybrewer.com
[email protected]