The flask or flash, a glass globe with a long narrow neck, was filled with snow water or crushed ice - the purest water available. It was then corked and inserted into one of the cups. Here it acted as a condenser or lens concentrating and whitening the candle light. Other flasks were prepared and mounted according to how many lace makers were working together.
By positioning the pillows around the flash-stool so that the candle light fell in a concentrated beam on each, three to five lace-makers could work comfortably by the light of a single candle. This is the origin of flash light.
Most of the flasks were especially made for the purpose but round bottles, oil flasks and engravers' flasks were all used.
Flash cushions, little open circles of plaited rush, were sometimes used as a rest for the flash . Hutches (baskets of plaited rush) packed with straw or rags, held and protected the flashes when not in use.
Flash-stools are mentioned in the Overseers' Inventories at St Paul's Church, Bedford dated 1772.