For this installment of Ask a Curator, we thought the question was better handled by one of our conservators, so we handed this over to Senior Conservator John Hirx.
Hannah asks: I’ve seen many Serra sculptures, whether it be the two sculptures in St. Louis (Twain and Joe) or at a MOMA exhibition, and many of these sculptures have been both inside or outside. With the use of the cor-ten steel, does the patina change inside the museum environment as quickly, if at all, like outside Serra sculptures? Obviously, if it changes, it does so in a slower process, but does that change the overall aesthetic of Serra sculptures? Are they best seen outside or inside?
Richard Serra, "Band," 2006, purchased with funds provided by the Broad Contemporary Art Museum Foundation, photo by Lorenz Kienzle
Serra’s work can be seen and experienced both indoors and out, as site-specific work or not—his work doesn’t seem to fall into an “either/or” category.
Seasonal weather changes support the development of the aesthetically desirable Cor-ten patina. Air quality probably plays a role as well. The environment inside of BCAM, in terms of relative humidity (RH) and temperature, is closely monitored—hovering at about 50% RH and 68 degrees Fahrenheit, with minor fluctuations. The museum air also circulates through an air-conditioning system. Therefore, patina development is slowed.
At its best, a weathered Cor-ten surface develops a forest of richly colored dark brown crystals. If the crystals are not disturbed during formation, the sculpture has a unifying, monolithic appearance even though the patina varies greatly from place to place. However, one rarely encounters this because the surface is so often disturbed in some manner. Keeping in mind that most of Serra’s Cor-ten sculptures are large and have enormous surface area, it is impossible for the surface not to be disturbed. Weather or human intervention can act to make the surface active, so when crystals are disturbed, time and the outdoor environment or a surface treatment support new corrosion or patina development. Therefore, the overall aesthetic is an ongoing work in progress.
John Hirx, Senior Conservator
Unframed The LACMA Blog 
In 1998, the first time Serra’s “Torqued Ellipses” were shown (at the Museum of Contemporary Art’s Geffen Contemporary), I vividly recall installation staff with hoses “watering” the giant Cor-ten behemoths many days in advance of the exhibition’s opening. (The ability to make a mess is one asset of the Geffen warehouse.) The aim was to encourage quicker “growth” of those surface crystals, in order to achieve the velvety surface. It worked like a charm.
No matter their final location, all Serra sculptures spend months or years undisturbed, exposed to the elements to establish a relatively even patina. A few years back, a group[ of artists curated a show, “”Invisible Graffiti: Magnet Show” where they hopped the fence and installed a temporary show on the oxidizing sculptures. There are some pictures here: http://lantuazon.wordpress.com/invisble-graffiti-magnet-show/
Looking at the tops of the Serras at LACMA, it’s fairly easy to make out the rectangular marks left by the clamps used to hoist the Serra in place. About 25 years ago I had the opportunity to see one of his tilted arcs moved. At the time, a hole had been cut to insert the cable used to lift the sculpture. Once it was is place, a little Bondo plugged the hole and a fake patina was applied to match the surrounding surface.
Patina aside, the works placed inside museums function very differently than Serra’s “public art.” Works like Tilted Arc were very confrontational into the viewer’s space, and in many cases, the public was confrontational right back. From artist David Hammons’ interventions on Serra’s work:
http://www.arts.ualberta.ca/~aoki/Teaching/objet_a/urine/Hammons/Hammons.htm
Or the UCLA student who use their Serra as a skateboarding surface, outside Serras wind up looking vastly different from inside Serras.
Thank you for the response! I saw Serra’s “Vortex” at the Modern in Fort Worth. I loved not only being able to walk through the piece, like most of Serra’s works, but to interact with it with sounds! I hope to make it to LA to see “Band.”