Carrier Context:
Unique Projects
Temperature and air flow studies in the chapel's vault show a geyser of warm moist air erupting toward the ceiling each time visitors enter the space in the morning. This warm air then spreads across the ceiling, cools and descends along the walls. In the process it deposits dirt and can leave behind its moisture if the ceiling's surface temperature is lower than that of the air. Moisture left behind on the frescoes' surface increases the chances for harmful chemical reactions, the formation of moulds or the deposition of salts as the plaster absorbs and then gives off moisture.
This is the paradox at work within the Sistine Chapel: Michelangelo's frescoes, especially after their cleansing, are creations to be shared with the world, yet the thousands gazing upward are the greatest threat to the Renaissance works. The goal, therefore, of the Carrier climate control system now operating in the chapel is to allow visitors by negating the effects of the moisture, heat and dirt they introduce into the atmosphere.
To surround the frescoes with atmospheric stability, the relative humidity of the air bathing the chapel's upper walls and ceiling will be kept at 55% (+/-5%) year 'round. Relative humidity is the most important single variable, because large swings would permit the porous ceiling plaster to "inhale" and "exhale" water vapor. This flow of water vapor into and out of the plaster could cause deterioration.
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