English Heritage

For her second summer work project at the Winterthur/University of Delaware Program in Art Conservation, Melissa had the great fortune of spending three months at English Heritage (EH) in London. She worked specifically in conservation science with Dr. David Thickett and Dr. Naomi Luxford. While there are many people specializing in preventive conservation in the USA, it is far more established as a major course of study in the U.K. The scientists at EH are well-known for their research in preventive conservation, and Melissa was eager to work closely with them.

English Heritage is a charitable trust that is responsible for the care of over 400 historic monuments, buildings, and places. These locations range from the world-famous Stonehenge to Eltham Palace, a 1930’s Art Deco-revived 14th century palace. Melissa worked specifically at Ranger’s House within conservation science, which supports the collections conservation team by offering analysis and research into preventive conservation research questions.

Figure 1. Ranger’s House in Greenwich (Source: English Heritage)

Background

Melissa was tasked with a specific research project that would offer the scientists a resource for better developing showcase designs. In order to understand the need for this research, Melissa visited many different sites around the country to see different stages of showcase design, installation, and the methods for monitoring the environment within showcases. The locations were spread across the country from as far north as Yorkshire to the southern points of Dover, Kent and Falmouth, Cornwall. You can read more about it here.

  • Using leak detection methods to prepare for air exchange measurements on new showcases at Richmond Castle
  • Comparing CAD drawings to new showcases at Richmond Castle
  • Using saturated salts for 3-point calibration of MEACOS RH and Temperature sensors
  • Inspecting a silica gel tray in a showcase at Eltham Palace
  • Melissa and Dave Thickett releasing CO2 into showcases at Ranger’s House to get new air exchange measurements

Research

Melissa conducted research looking into predictive models for passive humidity control within showcases. Controlling relative humidity (RH) is an important preservation technique that can prevent the growth of mold, corrosion of metal objects, splitting of wooden objects, and flaking of paint on composite objects amongst others. Many of EH’s collections are housed in ruinous castles and abbeys, and historic homes not designed to maintain a climate through mechanical control such as HVAC.

Figure 2. A moisture isotherm for silica gel shows minimal hysteresis below 30% RH, making it easier to model

It has been known that the RH within a showcase is dependent on the RH outside the case, the amount of sorbents within the case, and the air exchange rate for that specific case. For cases that require low relative humidity (below 30% RH) such as actively corroding metals, the EH scientists have been able to utilize a model (for 15 min, 30 min, and 60 min data intervals) to predict the relative humidity within a case with this information (see figure 2). This is a helpful tool when determining the amount of silica gel to put within the case and for determining certain specifications for designing cases.

Melissa was tasked with determining if there was a model that could be used for a similar purpose on mid-range RH (~40-60%) cases. She did this by comparing different models’ predicted relative humidity to the actual recorded relative humidity within cases using sorbents at mid-range RH. This model is complicated by the fact that organic objects are also typically buffering around this same RH range.

Figure 3. Melissa examining predictive models for RH within showcases using Excel

This internship was made possible through the Samuel H. Kress Foundation