Patina on Zinc and Copper

The Natural Weathering Process

Just looking out of the window from my home office, it is bucketing down outside. It is times like these that I am thankful for the canopies I have fitted on my front and back doors. Our front door is wood, and I am thankful for the protection the canopy gives it, meaning that it no longer swells during the cold and wet times. It is also nice to be able to stand under the cover whilst I open the door. I have had similar feedback from customers who have had our porches and verandas fitted.

The factory is ticking over very well but unfortunately, I have had to close our showroom to the public. The guys are constructing something very special in the factory – find out more in next month’s blog.

We recently fitted a copper clad canopy onto a log cabin and this has inspired the topic of this month’s blog. One of the most frequently asked questions is, “What is patina?” There are, of course, lots of different ways to answer this question. I am a keen watcher of antique and restoration programs on television where the word patina is used to describe a wide range of things including dirt, scratches, markings, weathering, damage by ultraviolet light and bleaching. However, when describing patina on zinc and copper this moves up a level.

I will now endeavour to explain patina on zinc and copper. As they say on the telly, other metals are available. Zinc and copper in their natural state are very bright and shiny, as demonstrated below on these Sarah Heritage door canopies. When people are purchasing natural zinc and copper door canopies, I tell them they will be shocked when the canopies arrive as they will be very bright and shiny. This shiny surface will not last long if not treated and a natural patina will soon form.

ZAC Blog January 2021 - Image 1
ZAC Blog January 2021 - Image 2

The above canopy has been newly installed and is yet to form any patina. I aim to track and share the process of the patina forming over the next few months. The picture below will show the formation of patina in the first week or so of its installation. All of this due to weathering. It is noteworthy that the patina forms an additional protective coating to the metal.

The day after installation, the weather gods unleashed a snowstorm, ideal for forming natural patina.

ZAC Blog January 2021 - Image 3

One week later the patina is starting to form on the copper and it is starting to appear darker where the elements have touched it.

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Looking closely, you will see the copper has a brown patina forming on the surface, the transformation is underway.

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It is useful to give information about pre-patinised zinc and copper at this stage and to help explain its benefits. Zinc and copper, as previously mentioned, are shiny when milled. All our zinc canopies are clad using zinc manufactured by VM ZINC and in fact, we have become a VM ZINC partner. We use two pre-patinised zincs to clad the canopies: Anthra and Quartz Grey zinc. The pre-weathering process involves a surface treatment to the natural zinc allowing a natural patina to form giving it a protective layer. It is not painted; the patina is part of an oxidization process forming a uniformed and very durable layer which is unaffected by UV light. A similar process can be carried out on copper. This will achieve a brown or green patina to the surface of the copper.

I am often asked whether the cladding on copper canopies can be treated so it forms a patina or Verdigris to the surface. It is important to say that we would never suggest treating a “pre-patinised” zinc or copper canopy. Natural zinc or copper can, however, be treated. There are lots of treatments that have been used to enhance the ageing process of the metal. I have experimented with some treatments including salt water, lemon juice, vinegar, copper oxide, Miracle-Gro, fruit juice, heat and even bird poo and pee. There are also lots of products on the market to help gain an aged patina on metal surfaces. I will be sharing some of these treatments and getting back to you in future blogs.

In my opinion, I would suggest leaving the patina on both natural zinc and copper to form naturally through the normal weathering process. It is very difficult to form a uniform patina as every piece of zinc and copper reacts differently to the process.

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