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Featured Rakow Research Library items from The Science of Glassmaking: Eight Centuries of a Magical Art.
This print shows a man standing “next to the stream where glass objects are made.”
This early book on metallurgy predates Georg Agricola’s De re metallica by 16 years. Chapter 14 of book 2 describes the process of making glass, the purification and remelting of glass frit, the structure of the furnace, the preparation of the pots, and the method of glassblowing. It also includes an illustration of a furnace.
The Mappae clavicula, which has been translated as “Little key of drawing or painting,” includes instructions for making, gilding, and staining glass. It provides a thorough treatment of pigments, and it is one of the earliest manuscripts addressing pre-modern technological materials and processes. The Rakow Library owns one of the most complete copies of this work.
This 12th-century manuscript by Theophilus was one of the earliest works to explain how a gather of glass on a blowing iron could be made into sheet glass or a hollow vessel. Theophilus also described the art of making stained glass, including recipes for coloring glass.
Johann Kunckel’s work is based on Antonio Neri’s L’arte vetraria (1612) and Christopher Merret’s translation of that volume, Art of Glass (1662). The plate illustrating male lampworkers in the 1679 edition has, for an unknown reason, been changed to show female lampworkers in the 1756 edition.
English translation of the manuscript text:
On chalcedony
To make a beautiful chalcedony
Take 25 pounds of crystal frit [and] 2½ pounds of red lead (vermilion), mix together, and throw into a crucible, and as soon as it is melted, take iron splinters, and sieve through a large strainer; then take another, finer strainer, and sieve that which issued from the first strainer, then take that which remains in the second sieve (because those that are too large, as well as those that are too small, are not good). Take from this 2½ ounces and throw into the crucible, mixing it well, let rest for 2–3 hours, then take ramina rossa [cuprous oxide], ¾ ounce, about 5 sazi [about one sixth of an ounce], and throw into the crucible, mixing well, and let rest for 5–6 hours, during that time mix 4 times, and let rest, then work it and it will be beautiful.
In this I have very little faith.
The alchemist who wrote these peculiar instructions must have had a reason for using mutton and lamb’s blood, but whatever properties they may have had that were deemed essential to the process of softening crystal are a mystery today.
“Take Borax zinj in powder, of fine white sand Zi melt them together in a large close crucible in the 2d chamber in the above furnace for half an hour: then take out the crucible & when cold break it: & at the bottom you will find pure hard glass capable of cutting common glass, almost like a diamond.
This experiment duly varied will lead us to very great improvements in the art of glass making, enamelling & making artificial gems
Universal Magazine for Aprill 1752, p. 166.”
“In the forefront there is an oval, roofed oven with two openings containing pans for melting. Glassmakers are dipping the tips of their long pipes into the molten mass and are blowing containers of various sizes. To one side there is an extension for cooling the glass, while on the other side an assistant is adding fuel to the deep oven.”
– Excerpt from the commentary on this illustration
De re metallica was first published in 1556. These detailed drawings are some of the first published illustrations of glassmaking.