Why Coat Bronze

Don't use wax on outdoor sculpture. And here's the research-based reasons why. I list the research at the end of this article, and full disclosure: I receive no remuneration whatsoever for any products referenced in this article.

First a little history. The use of wax with bronze has a long tradition. Archaeological evidence of the 'hot-wax' technique for creating bronze jewelry dates back as far as the first evidence of bronze itself - around 3500 BC. So I imagine that it wasn't too long before someone noticed how nice a bronze statue or pendant looks when polished with wax, and how it protects against fingerprints and weather. This is just a theory, but regardless of how it started, the use of wax to coat metal sculpture, particularly bronze, started long ago and continues today.

The Trouble With Wax

I've used wax myself on sculptures, such as traditional hot wax coating for outdoor bronze, and Renaissance Wax for indoor sculpture. Since most of my work involves outdoor sculpture, I wanted to know just how durable wax is. To my surprise research shows that wax lasts only a few months on outdoor sculpture. Furthermore, the development of new bronze coatings such as polymers protect longer, are easier to apply, and dramatically reduce the cost of maintenance.

So about 10 years ago and after thorough research I began using a polymer known as Everbrite. Though it's a proprietary blend, its ingredients include polymers which seem to me to be similar, if not identical, to Paraloid B44 which has extensive research. We also know that Everbrite has UV-protecting ingredients and a low VOC.  After 10 years of use, I continue to find advanced polymers such as Everbrite the best choice for outdoor bronze protection. Here's why.

The Advantage of Polymer

First, let's talk about application. Polymers are much easier to apply. Simply brush it on, and anyone can do it with careful attention to temperature, drippiness, and a very clean surface. If the bronze surface is too hot the polymer will streak rather than self-level. If it's too humid, the polymer will not stick properly and blister over time. And it's such a thin - very low viscosity - substance you need to watch out for dripping. Most importantly - because I learned this the hard way - the surface must be very clean especially of any previous wax coatings or the polymer will blister and peel within a couple years.

In contrast, wax application is difficult and time consuming, aka, more expensive. Wax has to be applied hot which requires an experienced conservator. Additionally, before applying wax, old coatings have to be removed and the surface cleaned. With Everbrite as mentioned above, yes, any dirt and previous wax has to be meticulously removed, but when it comes time to recoat Everbrite - anywhere from 5 to 10 years - previous coats do not need to be removed. Just recoat over the old coat. It 'self- anneals', meaning it chemically bonds to the previous coat. This is a huge plus over wax - anyone can do it, no expensive application, no expensive maintenance - meaning tremendous cost savings for our clients.

And cleaning a polymer coating is a much easier process of simply wiping with water and cloth.

Now let's look at another benefit of polymer, protection. Only in the last couple of decades have we developed the technology to determine just how long wax lasts. Research conclusively shows that even the best quality wax doesn't last as long as we thought and polymers last much longer.

How long wax lasts on an outdoor sculpture depends on the weather. We  took it as gospel that wax lasted a year or more when in fact research indicates as little as 3 months in outdoor conditions! It's so variable that wax on one side of a sculpture weathers more than another side. To know just how long wax lasts, you need to test the particular sculpture which is a time-consuming and expensive process. Without such testing it's only a guess how long wax is protecting an outdoor sculpture. And here is the real danger: if your wax application lasts only several months, the harsh acids of bird droppings, acid rain, and pine pitch can damage and discolor a bronze patina before your next annual wax application.

I found that on 3 sculptures located in the harshest outdoor environments (freeze-thaw marine) 2 coats of Everbrite last 4-5 years. In less harsh environments (freeze thaw but not marine) several sculptures I coated in Everbrite are still showing no signs of wear after 7 years.

And all polymers are reversable with solvent. Any solvent will do, though xylene does not evaporate quickly so it's able to break down the polymer coating more effectively than other quick-drying solvents. But xylene, like all solvents, is harmful especially to lungs and skin so protection is critical. By the way, any solvent will not harm the common hard chemical patinas applied to bronze sculptures in the foundry. Solvent will remove painted patinas.

Everbrite also provides UV and anti-oxidant protection, and does not yellow. Frankly, I think it's simply nonsense to ever use wax again on outdoor sculpture.

Assessing Different Polymers

I rely on the US Park Service and the Getty Conservation Institute for the latest research on best products and practices. Unfortunately they have not yet studied recently-developed polymers. They have studied the earliest ones (Incralac and Permalac) developed in the 60's which they found superior to wax.

By the way, when you search for polymers you will find many other terms - acrylic polymer, synthetic polymer, acrylic resin, lacquer - all of these terms refer to a particular kind of polymer so to keep it simple I'm calling them polymers.

Incralac was the first. Improved coatings followed with Permalac. Everbrite was developed in 1990. Now there are many. I've used Everbrite for the last 10 years with excellent results.

According to Getty research, Incralac lasts a little over a year in the harshest environments, but top-coats of wax can extend its life up to 3 years. This wax coat means that when it comes time to apply a new coat of Incralac, the wax needs to be thoroughly removed. Permalac last 3-5 years with 4 coats. Everbrite lasts 5-10 years with 2 coats and does not need to be removed when it comes times to recoat. All the latest polymers provide UV protection, self-anneal, and self-level.

Everbrite provides any gradation of satin or matte finish desired. Permalac now comes in a satin finish but as of this writing (2025) no gradations. A cautionary note: the method of coating Incralac with wax was developed by the Getty Institute to improve its durability and provide a wax look. I've just heard of a conservator who uses this technique on Everbrite, that is, coating Everbrite with wax. First, this does not in any way improve the surfaces of the latest polymers including Everbrite. And second, the wax will have to be thoroughly removed before applying a new coat which uselessly increases maintenance costs.

Surprisingly - and happily! - I've also found that Everbrite on bronze helps protect against graffiti - more about this in the case study below.

For cost, protection, and ease of application I prefer Everbrite.

The Downside

One criticism of polymer is that it cracks and peels allowing water to seep in and discolor the bronze surface. Yes, I have seen this and it's entirely caused by not thoroughly cleaning the surface before coating. Often this is wax residue from a previous treatment. I've made this mistake myself and learned the hard lesson which I repeat for emphasis: thoroughly clean the surface of bronze before applying any polymer. When cleaned properly I have not seen any cracks or blisters or peeling in dozens of applications.

Another criticism is that it's too shiny or just doesn't produce the same look as wax. This was true for early versions, but not any more. Everbrite, for instance, comes in any shade of satin or mat finish desired. In fact, the case study presented below is an example of just such a test of many different shades before the artist found the perfect match for the original wax look that he preferred (1/4 matte).

A downside of any polymer is that it darkens verdigris. But I found a solution for those who wish to preserve the beautiful shades of green oxidation on their sculpture. I apply a faux-verdigris by painting the polymer coated bronze surface with acrylic pigments to match the original bright verdigris. Then I coat the acrylics with another coat of Everbrite - polymer does not darken color-fast acrylic paints. The verdigris look is preserved and the sculpture is protected.

Final Thoughts

One drawback is that any polymer is solvent-based so it's flammable and can irritate skin, eyes, and lungs. Thus, gloves, respirator, and eye protection must be used. Some plastic containers and brush bristles will melt on contact with these polymers, so I use metal containers and natural-hair brushes, available at any hardware store.

The final comparison is expense. When you think about all the issues mentioned above, polymer is dramatically easier to use and less expensive than wax.