Friday, December 9, 2011

It's Hammer Time

A selection of snowball hammers.
Did you know that Shelburne Museum has one of the largest collections of snowball hammers in the nation? Do you even know what a snowball hammer is? I definitely did not before I started working here.

Snowball hammers, also known as snow knockers, are used to remove excess snow and ice from horseshoes. Most hammers are made of iron and often have snap rings or hooks that can easily clip onto a horse's harness.

Our snowball hammer collection includes many varieties from early America. Blacksmiths gave snowball hammers, like the ones featured on the left, as gifts to customers. The hammers served as small tokens of appreciation for their loyal business, as well as a way for blacksmiths to practice and demonstrate their skills.

Recently, I traveled to some co-workers' houses to groom their horses and further investigate snowball hammers. While iron hammers like the ones in Shelburne Museum's collection are not often used today, you can definitely see how they would come in handy.

Habibi models a snowball stuck in her horsehoe.
Snowball hammers: Yet another example of the wonderful things you'll find at Shelburne Museum!
Sandy Sock's hooves are snow free!

Wednesday, December 7, 2011

Looking into the Light

Have you been considering using LED (light emitting diode) bulbs for your home or business? This rapidly-developing class of lighting fixture has generated quite a buzz. Since we've been researching and using LED bulbs in some of our galleries for about eight years now, other museums and collectors have been asking us if LEDs might be right for them too.
LED lights have illuminated the dollhouses and cases in the Variety Unit since 2004
Finding an exhibition design solution.
In 2004 Shelburne Museum installed LED lights in the Variety Unit's doll and scrimshaw cases primarily to solve an exhibition design challenge. While we'd prefer to keep lights out of the cases entirely, it just wasn't possible to light the objects from outside the cases given the relatively low ceilings in this 1835 building. The qualities we were looking for were: no ultraviolet content, low heat and even light. Director of Preservation and Conservation Rick Kerschner looked at a number of options and tested the most promising ones in a mock-up dollhouse room in the Conservation Lab.

Our mock-up dollhouse room with the monitor and some of the lighting options we considered
If you're interested in the details, he outlined his process in a presentation at the New England Archivists Meeting at Simmons College in 2008, now available as a podcast.

Ultimately, Rick settled on LED bar lights from Prolume. There were several reasons for selecting this company. Their bar-shaped fixture was a size and configuration that met our needs. The small company was also willing to create a light that was the appropriate color (3000 degrees K) and intensity to show off the collections to their best advantage. In addition, Prolume guaranteed that there would be no significant drop-off in the amount of light emitted from these bulbs for 10 years and that the light would not decrease by more than 50% for 15 years. Unfortunately this first generation of LED lights didn't live up to the estimated longevity and lost most of their light after only a few years of use. Prolume honored their guarantee and replaced all of the lights with their third generation LED bar lights containing diodes manufactured by Nichia. These new LED fixtures have been in place for over three years, and we have seen no loss in light intensity.

Note the differences in color among the first generation LEDs (top) versus the third generation LEDs (bottom). The diodes on the bottom are more uniform in color in contrast to the lights on the top. Its subtle, but it makes a difference.
So how many museum professionals does it take to screw in a light bulb?
In fall, 2010, Efficiency Vermont offered the museum a sweet deal - a full rebate on all the LED lights we cared to purchase (but only until December 31, 2010)! While conservators love free stuff just as much as anyone else, there were questions about the nature of the light emitted by LED lamps as compared to the more commonly used incandescent and halogen lights. We needed to know whether the light generated from the LEDs would be any more damaging than the light generated by the halogen lamps we were used to. Additionally we wondered if commercially available LED lights had the same color and intensity consistency that Rick had been only able to achieve for the Variety Unit cases by working directly with the manufacturer.

So as other institutions, including the National Gallery in London and the Getty Conservation Institute, were looking at commercially available bulbs in their labs to determine how the nature of light generated by an LED compared to fluorescent and incandescent lamps, Rick did some practical research in our galleries. He mocked up up comparisons and showed them to the electrician, exhibit designer, curators, director, and anybody else who had an interest in how the buildings were lit. Although Rick paid close attention to the color rendering index (CRI) of the LEDs, in the end, what was most important was how the artifacts actually appeared under the lights. Informed by the research done at other institutions and our own mock-ups, Shelburne Museum staff decided that the Philips EnduraLED MR16 and Sylvania UltraLED PAR 20 and PAR 30 LED replacement bulbs worked best for responsibly displaying our collections in our buildings with low ceilings.

Rick Kerschner, Exhibit Preparator Doug Oaks and Electrician Rick Gage have been generally pleased with the performance of these bulbs over the 2011 season. In total Shelburne Museum received over $50,000 worth of bulbs through Efficiency Vermont's "free LED" program. Rick estimates the yearly energy savings to be about $6,000; so payback will take about 10 years. Although the bulbs are rated for about 40,000 hours (or slightly more than 32 Shelburne Museum seasons) Rick is not convinced they will last that long. It remains to be seen how cost effective these bulbs really are.

More links to sources of information about using LEDs for exhibition lighting can be found on the American Institute for Conservation's website and within the LinkedIn Museum and Art Gallery Lighting discussion group. The Getty Conservation Institute's Guidelines for Selecting Solid State Lighting for Museums is available on request from their website.