Making Mirrors

12-10-2019

'The history of the looking glass throughout the world is interwoven with tales of wonder mixed with fear and superstition.' So begins Geoffrey Will's volume on English Looking-Glasses, which continues with long-standing legends and beliefs surrounding reflections and mirrors, which, along with their material fragility and high cost, has accorded them value and esteem. Mirrors can prove to be wonderful additions to any home, adding depth and light to different spaces. As you will see from the photographs below, the galleries of Reindeer Antiques have many on display, varying in size and style to suit any taste. However, making mirrors in the eighteenth century was no easy task, and mirrors which survive with original glass are rare and highly prized.

 


The notorious difficulty in manufacturing glass specifically for mirrors is attested to by Robert Dossie's notes in his Handmaid to the Arts. 'The glass for forming the looking-glass plates in perfection is the most nice and difficult to manage, of any whatever'.  Glass was made by melting silica (usually from sand, flint or quartz) which fuses at high temperatures. Many other ingredients can be added to create different formulae for different qualities of glass to meet different needs. Dossie offered a formula for the 'best composition of glass for looking-glass plates' which was not only difficult, but also prohibitively expensive given the quantities of different materials used: 'this composition is not to be made without expense'.

The flat glass plates required for making mirrors were formed in two ways. The first was casting. A relatively simple process in which molten glass was poured into a mould. Once poured, the molten glass took the shape of the mould and was removed after having been allowed to cool very slowly, in a process called annealing, which improves the stability of the material by reducing internal stress. The second was the more complex 'broad' process. This required molten glass to be blown to form a sphere, which was then rolled to form a long hollow cylinder. Once the cylinder was formed its ends were cut off, leaving a tube, which was cut down the length and rolled out into a flat sheet. Once rolled out flat, the glass was annealed. Despite being the most difficult of the two forming processes, the ‘broad’ process was the most economical for raw materials and the most widely practiced until the nineteenth century.

 


Making mirrors required more than just flat panes of glass however, and the other processes required to finish them were undertaken by different tradesmen. Once the glass had cooled, it was ground and polished. The glass was first ground by employing coarse abrasives to remove visible marks and ensure the glass was smooth. Once these were removed polishing with finer powders until the glass had reached its desired state. A further process added yet more refinement to certain glass plates. ‘Diamond cutting’, which we would now call bevelling, created a taper towards the edge of the glass. The tactile quality of original ‘diamond cutting’ are often taken as an indication of original glass being retained in period mirrors.

 


Finally, the ‘foiling’ of the glass was the process which transformed a sheet of glass into a mirror, with the addition of a reflective material. A contemporary explanation from Dictionarium Polygraphicum observed that ‘a sheet or leaf of tin’ is laid on a table, over which mercury is poured. The glass is placed on top and pressed down to draw out any extraneous mercury and to help the tin adhere to the glass. Once dried, the mirror is complete.

 


As well as wall mounted mirrors, mirrors set in a four-legged frame are known to have been of use. These were known as cheval or 'Horse Dressing Glasses', due to the four-legged frames which supported them. This early Georgian cheval mirror, recently sold at Reindeer Antiques, is rare example from the period. Sheraton, in his Cabinet Dictionary of 1803 accurately describes its mechanism. The glass can be raised and lowered thanks to weights ‘in the manner of a sash window’

Geoffrey Wills, English Looking-Glasses (Country Life, 1965)

Robert Dossie, The Handmaid to the Arts (1758)

Dictionarium Polygraphicum (1735)

Ralph Edwards, Dictionary of English Furniture, Vol.II (Country Life, 1954)