Ongoing Conservation

One of the more unique parts of my role at the Roman Baths involves the conservation of the monument. As you go around areas of the monument you will see the natural wear and tear of a site such as ours, nearly 2000 years old, and still being walked on by 100, 000s of people a year.

In order to preserve the monument we carry out a programme of work to stabilise of the monument that may be more fragile than others.

Around the walls of the Great Bath, you will see substantial areas of surviving Roman wall plaster; what you may not have noticed is that below this plaster (and sometimes about it), there is often a line of mortar, which differs slightly in colour and make up.

Spraying newly mortared wall to ensure it sets

 This line of mortar is known as sacrificial mortar. We apply it next to the Roman plaster to provide a barrier for the Roman remains, taking moisture away from it and supporting and preserving the Roman layers, more substantially than if we were to leave it unprotected against the elements.

We use the same types of ingredients for our mortar as the Romans would have done; lime, brick and sand, but the composition we use differs. If you look closely at the surviving plaster, you will see mortars with quite large chips of brick in, this tends to indicate that it is original Roman mortar (we use smaller brick chips in our modern mixes). We mix our modern mortars, to look similar to the Roman, but distinct enough that it can be seen where, the original lies and where the sacrificial mortar has been added.

Modern mortar below existing Roman plaster

Last month, I was down by the Great Bath, replacing some of the sacrificial mortar which had fallen away. The mix I used complements the Roman mortar nicely, not being too different so as to stand out, but still making it easy to spot where the Roman mortar ends, and my additions begin.

Verity