Sunday, February 24, 2013

Brewing With Copper - Verdigris Myths

A little over two years ago I published a post on constructing a 5 gallon mash tun using a round Gott type water cooler and parts readily available from Home Depot and other hardware stores. Since then I've actually built another one using the same parts list and have made wort with them to brew all styles of beers including IPA, Stout, Rye, Wheat you name it.  The design has proven to be very reliable and I'm happy to say I've never had any issues with either of the tuns I've built, no stuck sparges or leaks of any kind.

12 Gauge Wire Coil Inserted To Prevent Collapsing The Braid

Recently someone raised a question about using copper in the brewing process and the possibility of verdigris poisoning caused by wort coming into contact with copper. If you've ever seen copper roofs, drain pipes, statues or the water lines in some homes that have a green colored patina, well that is what's formally called verdigris. It's been documented that you should always wash your hands after touching any copper metals that have a coating of verdigris because in large enough amounts it has been reported to cause nausea and vomiting.

Inspection Of Copper Inside Braid After More Than 2 Years
The issue of verdigris contamination when using copper parts in the brewing process had come up while I was designing the mash tun and I had found out is was not a concern for several reasons. Of course brewers have been referring to their kettle as 'the copper' for centuries since they were in fact made from copper. I also read a Brew Your Own magazine article titled Metallurgy For Homebrewers that explained copper's role in brewing that dispelled a lot of myths surrounding verdigris.

"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

After Hundreds Of Mashes Not A Hint Of Verdigris Anywhere

I tore down my braided hose and inspected all the copper and brass parts and found no signs of verdigris at all, what I did find is just as John Palmer had pointed out, the parts all had the stable oxide layer and dull copper color that protects the wort from verdigris. The copper and brass parts are no longer bright and shiny as they once were when I first assembled them for use in the mash tun designs, but they are protected by the stable layer of oxide that continues to protect the wort from picking up any dangerous contaminants.

Inspected, Reassembled And Ready To Go

As for cleaning and maintaining the mash tuns all I've ever done is remove the spent grains and thoroughly rinse out the insides with clean water until there were no grains left inside. Then I just turned the tuns upside down with the top facing down on a towel and a small air space under one side so all the water drained out. Once most of the water was drained I turned them right side up so they just could air dry. I've read posts in some forums where white vinegar and salt, or StarSan was used to clean the copper parts and get them shining like new. After reading John Palmer's article I decided I'll just use clean water to remove and bits of grain and keep the protective oxide layers that have already built up on mine.


  1. We drink out of copper pipes daily, every house I know of has them. Newer homes in my area have switched to a PVC style pipe (or PEX) because of the hard water and it's effects on copper piping. Its just horrible what it does to your plumbing, fixtures and toilets.

    I would have thought you would have switched to a Coleman style cooler by now. The last straw for me was a really nasty stuck sparge, when I told the guys at keystone (HBS) about it they said I had reached the limit of my container.

    The vertical design of the 5 gallon cooler compressed the grains too much. By switching to a 62 quart cooler I was able to spread out the grain and this eliminated my stuck sparges. It also allowed for larger batches. At that time I also switched from fly sparging, to batch.

    I also found the water line I used was too much of a pain to keep clean and there were sharp edges. By switching to a bulkhead and a bazooka screen I was able to clean and remove every part of the coolers wort filtering system. I could even put the screen in the dishwasher (stainless) and sanitize it.

    Your design was spot on, I made a lot of good beers. The price of a bulk head and a bazooka screen is so small that I would have gone that route the first time if I had known better. A Lot of the the fun is making your own equipment, maybe its time to build a larger masher and move outside to do bigger boils? I think the larger cooler makes a difference, the water line vs bazooka screen is debatable.



  2. Thanks for the honest feedback John, I'm happy to hear you've found a design that works better for you. So far I've managed to mash up to 14.5 pounds, of all types of grains including flaked rye and wheat, and never had an issue yet with a stuck sparge even with 8.7% ABV recipes.

    As for having the 10 gallon capacity I've built two 5 gallon mash tuns instead and they both get great efficiencies. The smaller sizes allow me to mash two different recipes on those rare brew days when I get to brew 10 gallons.