By Carla Paulis

11 May 2018

Conservation of the Painted Hall has been underway since 2012. The conservators are using carefully tested and non-invasive cleaning techniques to remove decades of dust and dirt, revealing the splendour of the paintings below. Sixty years have passed since the paintings were last cleaned in the late 1950s. The current project is allowing us to study Thornhill’s ceiling in greater detail than ever before. One of the most exciting things about getting up close to the paintings on the observation deck, is the opportunity to spot what I like to call ‘ghostly details’. 

Thornhill’s great ceiling is vast, measuring around 30 metres long by 15 metres wide. It is not surprising that as the artist and his team of assistants worked away they sometimes changed their minds, adjusting the composition slightly by painting over earlier details. They used oil paints on a dry plaster surface, building up the painting in layers or glazes. This technique is sometimes called fresco secco in Italian. Unlike true frescos which have to be painted quickly whilst the plaster is still wet, Thornhill’s technique allowed him to make small adjustments by painting over earlier paint layers. 

These adjustments or alterations are called pentimenti (from the Italian verb pentirsi, meaning to repent or change your mind). Pentimenti are usually hidden beneath a subsequent paint layer but in some instances they become visible because the paint layer above has become more transparent with time. They can also be detected using infrared light. They are interesting because they show the development of the artist's design and how his ideas evolved. 

One very clear example is visible near the hand of the rosy-cheeked cherub, above the goddess Athena. If you look carefully you can see the shadowy outline of a set square and possibly some billowing drapery above and to the left of his head which have been painted over at a later date. Sometimes changes were less dramatic, such as the slight repositioning of a foot or hand. In the second image below you can make out the trace of a line of red toes where the foot was once positioned higher up.

Can you spot the shadowy outline of a set square in the cherub's hand?

In this example, the foot of a winged figure above the Spanish galleon at the east of the ceiling has been repositioned slightly lower down.

The West Wall depicting the Hanoverian George I and his large family has some even more dramatic examples of pentimenti. To the left of the dome of St Paul’s Cathedral you can make out a curved shadow, showing its original position. Even more intriguing is the ghostly outline of a hand on the stone steps below the royal family. Could this be George I’s adulterous wife, literally and metaphorically swept under the carpet? To find out the answer and spot many more examples of pentimenti book your ticket for a Painted Hall ceiling tour!

The curve to the left of the dome of St Paul's Cathedral indicates its original position.

Who does this ghostly hand belong to? Hone your detective skills and come and discover some of the many pentimenti, or ghostly details, for yourself.

Find out more