↓ Expand ↓

Artful Science

» About This Blog

Category → plastic

Two-Faced Microbes: Dirty Fungi And Cleaning Bacteria

King Tut's tomb with brown spot stains. © The J. Paul Getty Trust, 2001

Microbes can be an ugly pain-in-the-butt for artifacts.

Even if the bacteria and fungi growing on heritage buildings, frescoes, space suits and archival documents can be killed, they often leave behind some rather unpleasant stains that are really hard to clean off the sensitive surfaces of artifacts. That’s the situation in King Tut’s tomb, for example, where fungi have left behind dark brown spots on the beautifully painted walls.

Today the Harvard Gazette wrote about this issue: At the request of Egyptian heritage officials, researchers at the Getty Conservation Institute swabbed the walls of King Tut’s tomb, and sent samples of the brown muck to Ralph Mitchell, a Harvard microbiologist who specializes in cultural heritage science. Getty chemists figured out that the dark spots are actually melanin–the same pigment that builds up in your skin when you get a tan–while Mitchell’s team figured out that the fungi are dead and probably won’t be producing any more browny spots. Mitchell thinks that the fungi initially grew because the tomb was sealed before the paintings inside were dry, suggesting that the teenage king was buried in a hurry. The still-wet surface thus provided tempting real-estate for melanin-producing fungi.

Cyanobacteria growing on the Luca Signorelli frescoes in Italy's St. Brizio Chapel caused a rosy discoloration. Credit: Wikimedia Commons.

It turns out that melanin-producing fungi have also stained marble in Italian cathedrals after an ill-advised attempt to protect the marble using acrylic polymers. The acrylic on the marble attracted the staining microbes who found the plastic to be a tasty meal. But microbes will also grow on buildings, art and artifacts that haven’t received unwise “protection.” For example, orangey carotenoid pigments are often left behind by bacteria on stone buildings, Mitchell says, and frescoes have been stained rosy red due to the phycoerythrin pigments produced by cyanobacteria.

The question remains: How does one remove these unfortunate discolorations? Continue reading →

Diagnosing The Devil Inside

Using the new non-invasive technology on a plastic statue (left), the researchers were able to show that it is composed of nylon (blue) and cellulose acetate (red). Credit: Anal. Chem.

Similar to a disease, chemical degradation often advances quietly in art and artifacts, without any external warning signals. That is, until a breaking point occurs, and museum staff are suddenly faced with a faded painting or a cracked sculpture.

Like doctors who want to diagnose patients at the early stages of their illness, when treatments are more likely to work, museum conservators also want to assess the health of cultural artifacts at the initial stages of degradation, and they want to do so non-invasively–that is, without taking a blood sample.

Now Matija Strlic at UCL has just published an article about a new diagnostic tool that can visualize the internal degradation of artifacts before the damage is apparent to the naked eye.

Continue reading →