Two New Cobalt Hygrometer Postcards in the Shop
Two Victorian-styled weather cards, "The Gentleman with an Umbrella" and "The Apothecary Shop", have joined the online shop.
Both cards use the same old trick: a cobalt-chloride coating applied to one element of the illustration, which shifts colour with the moisture in the air — blue for fine, violet for change, pink for rain. On the the working part is the gentleman's umbrella; on the , a large apothecary bottle, which — with a certain honesty rarely seen in advertising — carries the label , . The jar names exactly what makes the card work.