Ash is a remarkable substance. You can use it to steady your footing on an icy path or to fertilize some of the plants in your yard. Quite unintentionally, it also has been used to preserve art.In ancient Herculaneum, ill-fated sister city of proud Pompeii, many of the citizens of the Roman empire who dwelt there were wealthy patrons of the arts. However, their taste in the finer things in life did not save them when nearby Mount Vesuvius erupted in A.D. 79, covering the city in hot volcanic ash. Herculaneum and Pompeii, along with at least two other nearby towns, were buried and forgotten for centuries to come.Found in the ruins of Herculaneum near Mount Vesuvius, this ~2000-year-old bust is shown with its original painted hair and eyes. Images courtesy of the Warwick Manufacturing Group at the University of Warwick.The remains of Pompeii and Herculaneum began to reveal themselves in the 18th century and have been the subject of ongoing research since. The first human skeletons, in fact, were discovered in Herculaneum only in 1981. More recently, archaeologists found a statue of an Amazon buried beneath the ash. Most remarkably, the beautiful warrior has retained her colour.It is known that ancient Romans painted some of their statuary – flakes of pigment have been discovered before – but erosion from the effects of handling, atmospheric chemicals or UV radiation has taken its toll over the centuries. Not so with the Herculaneum bust: Covered by volcanic ash, the painted hair and eyes are as luscious as ever.The statue, which was discovered by the Herculaneum Conservation Project, recently was turned over to the Warwick Manufacturing Group (WMG) at the University of Warwick in the UK. Workers with WMG and with the University of Southampton and the Herculaneum Conservation Project are studying the artefact and its paint job while handling it as little as possible, using laser scanning along with computer graphics and prototyping tools.After four hours of scanning with a laser and camera system, researchers generated this 3-D computer graphic of the bust.According to Dr. Mark Williams of WMG, the group uses a laser scanning system from Metris of Louvain, Belgium, to acquire up to 80,000 measurements per second. With the system, a laser line flickers across the subject, and a camera registers the resulting reflections. Each point on the bust then is triangulated, providing a resolution of 50 to 60 μm. The dense pack of data subsequently is used to re-create the art in three dimensions, using both computer graphics software and a physical “rapid prototyping” material.The group then used the laser-generated data to create this physical model of the bust.The data is sufficient not only to enable the researchers to study how the paint was applied to the statue but also to allow them to simulate repainting it in a 3-D model.