studio al fresco
Yesterday the confluence of an absolutely gorgeous day and the need to work with some particularly noxious chemicals had me packing some of my studio gear and working out on the back porch of the studio.
The big project of the afternoon? Patination.
When silicon bronze is initially cast, the raw metal is kind of a bland color. Over time, the surfaces will darken via oxidation. Of course, the warm color isn't just for show; that tiny layer of oxide build-up also protects the surfaces of the castings from corrosion.
Without patination, it's kind of bland.
As handy a natural phenomenon as this might be, Mother Nature isn't likely to finish the job before my next opening. In order to speed up the process, metalworkers apply a variety of chemical oxidizers to forcibly create patinas on metal. Each chemical has a different effect, which will vary based on the metal it is applied to and the method by which it is applied.*
*If you're interested in a ridiculous amount of metallurgical nerdity on this topic, check out The Colouring, Bronzing and Patination of Metals Richard Hughes and Michael Rowe.
Silicon bronze's innate resistance to corrosion is an excellent attribute, but it also makes this entire process even harder. My first collection of bronzes narrowly avoided failure, simply because I couldn't find anything strong enough to cut into the surfaces.
Which brings me to yet another note to the metallurgically nerdy: Seriously, be really careful about searching up a random recipe for a bronze patina and experimenting. While it's possible fortune might smile upon you and darken your metal, some of these mixes are really dangerous.
Even worse, they may kill you while not working at all.
Most of the classic recipes in the public domain were formulated for use on the older style zinc-based bronzes. These alloys went out of common use back in the Eighties, replaced by more durable and workable silicon-based alloys.
These modern metals will laugh off most of the classic methods of coloration. Usually at four in the morning, two days before your show's opening. Trust me, I'm wise only from experience.
Fortunately, that same "wisdom" led me to discovering a mix that worked pretty well. Unfortunately it's also caustic, flammable and toxic.
Around here, we call it The Soup.
This lovely concoction is slowly raised to near-boiling temperatures, at which point the fumes alone are strong enough to rust lesser metals. It also can do a number on your lungs, which is why I was so thankful for the pleasant weather.
Three rounds of dip, wipe, dry and repeat gives you something...disgusting, but dark.
No really, this is a good thing.
From this stage, the pieces are left to rust for a day, and then I start the slow process of polishing the uppermost surfaces back towards a shine. This will leave the lowest areas the most darkened, and the patina that got into the pores of the metal will (hopefully) color the entire piece beautifully.
You can see the results of this mad science in about two weeks, at the Spring Art Mart.
04 / 09 / 2010