As children we used lemon juice as invisible ink. It was important first to clean the nib well in order to remove any contamination from Stephen's Blue/Black ink. After writing your secret in invisible ink just like real spies one could make it appear by holding a candle under the missive. So by magic (science didn't exist in those days) the secret would gradually appear. This phenomenon can also be achieved with mutton stew, a pressure cooker and white painted plaster. As far back as I can remember as a child there was a stain on the kitchen ceiling shaped like some kind of animal, perhaps a walrus. Every few years Dad would paint the ceiling and it would disappear.....but only for a while. Gradually, just like invisible ink when heat was applied it would reappear. This particular feature was not advertised by Prestige whose pressure cooker and other kitchen utensils were the most desired by housewives of the 1950s. The quality of the steelwork and the riveted wooden handles made a Prestige kitchen second only to a fitted carpet in dreamland.
Although the Prestige name still exist the manufacturing has gone east. The site of the original factory is now a retail park but a reminder of the contribution of Burnley workmanship is provided by this Art Deco building and the decorated pavement in front of it. This has been paid for by J Sainsbury who have a store next door. I find it comforting that this company's support of The Arts is not restricted to the grand gestures.