What does mould look like?

Due to age, storage and usage, archive and library collections may be soiled and discoloured, making it difficult to tell the difference between mould growth and historic dirt deposits. As such, identification of mould is not always straightforward. However, there are several key characteristics to look out for which may indicate its presence within your collections.

Common visual indicators can include:

  • Staining, mottling and/or discolouration of the affected surface, frequently in a circular pattern and in a variety of colours (Fig.2-4)
  • Water damage and/or tide marks – where contact with moisture has occurred, mould growth is common (Fig. 5-6)
  • Surface deposits – mould that is actively growing, or powdery accretions of dormant mould (Fig. 7-8)
A bound document, showing the front cover and spine of the closed book. The covering is black, and has been scratched and damaged. Across the surface are also clear small white blooms of mould.

Figure 2 – catalogue reference FO 277/215

A selection of original paper records in a pile. Some have been lifted up to reveal the extent of the dark mould staining present - the stain patterns are the same on the underside of the document being lifted, and the topside of the document directly beneath it.

Figure 3 – catalogue reference WO 78/4369

An aged manuscript book, opened to reveal severe discolouration and mould staining.

Figure 4 – catalogue reference E 190, piece number unknown

Two severely damaged bound documents, shown side by side. Clear tide marks can be seen on both.

Figures 5 and 6 – IR 58/21229 and ADM 38/3722

Close-up of an original paper document, displaying significant blooms of black mould.

Figure 7 – catalogue reference AO 3/877

Close-up of original planning papers, with a hand at the top of the image lifting part of the pile to reveal significant black mould staining.

Figure 8 – catalogue reference WO 78/4369

The science of mould has additional information on how mould grows.