Summary: over 400 works ranging from J. M. W Turner to French artists of the Barbizon school and 20th century artists with local connections such as Noel H Leaver, who is represented by 34 works.
The earliest part, collected before 1919 are local topographical works. After 1920, the Massey Bequest allowed the regular purchase of watercolours by well known artists such as William Henry Hunt, David Cox and Myles Birket Foster, culminating in the purchase of Cape Colonna by J M W Turner in 1960. After 1960, the purchases were mainly by artists with local connections such as Noel H. Leaver, Hugh Gresty and James Spencer Taylor or relating to Towneley and the Towneley family.
Gifts and bequest account for about half of the collection, of which 36 were donated by Wilfred Dean between 1924 and 1940 including ten drawings by Millais.
Whilst parts of the collection are regularly displayed, care is taken not display any individual painting too often in order to preserve them from fading. In 2010, a joint exhibition of British watercolour painting was undertaken with Gallery Oldham. This was sponsored by the Heritage Lottery Fund and allowed around a dozen paintings to be conserved before the exhibition. A rolling conservation programme is in place based on a conservation report produced by Lancashire Conservation Studios, Lancashire County Council Museum Service in July 2103.
The basic details for all the paintings are recorded in the Modes database. Index cards for each of the watercolour paintings were started in 1973 but have not been updated since 2004. Not all detailed information from the index cards has been added to the Modes database.