The following extract from 'A Second Dudley Book of Recipes' (1914) provides the Countess of Dudley's tip for how to keep butter fresh in the 1910s.
The first fridges fit for home use were invented c.1913 by Fred W. Wolf of Indiana, USA and the first electric fridge was invented the following year by Nathaniel B Wales of Michigan, USA; the same year that this book was published. It would be many years before domestic fridges would be readily available in the USA let alone the UK, and many decades before these would become a common fitting in the typical UK household.
We might therefore expect that the Countess's suggestion for how to preserve butter in a shallow dish containing cold water and laying a damp muslin cloth over the top of the butter will have been tried and tested for many years after the book's publication.
TO KEEP BUTTER FRESH
Georgina, Countess of Dudley, 1914
Butter can be kept perfectly sweet and cool by being wrapped in a damp muslin cloth and placed in a shallow dish containing a little fresh cold water, the cold is produced by evaporation, the cloth absorbing the water.
The muslin cloth should be previously steeped in water to remove all soap, etc.
Original Recipe for 'To Keep Butter Fresh'
'BOOK 3': A Second Dudley Book of Recipes (1914)
Collected and Arranged By: Georgina Ward, Countess of Dudley
Publisher: Hutchinson & Co. (Paternoster Row, London, England, U.K.)