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The experts at the Frei Co. work with committees for months to educate them about stained glass and to create a design that is meaningful for their church. The Frei Co. never uses the same design at two different churches and does not keep a catalog of its designs. Once the committee approves a design it is blown up to scale and drawn out on huge sheets of paper that are used in multiple steps of the process. The company does not usually keep the patterns after the windows are completed, but instead give them to the church for their safe keeping. If a repair is needed later, it is then easier to obtain the pattern. Once the pattern is ready, the glass is chosen that will be utilized in the window.
First the artist chooses the colors and textures of glass to be used. They must be trained to understand how to make these elements work together or the window will fail visually. The artist’s pattern is then used to determine the cut and size of the glass. A case-hardened steel wheel on an axle, or a glass wheel, is used to score the glass. Then glass pliers, which differ from normal pliers because they are flat on the inside with no ridges, are used to snap the glass. The line creates a weakness in the glass and tells the glass where to crack. Curves are very difficult and sometimes require multiple cuts. If a cut is not smooth a grinder is used to take out the rough edges and a diamond saw is used for tight corners. Once cut the piece is ready to be painted.
Metallic oxides are applied to the glass. Generally any color that the artist wants is done in the cutting process, and then the oxides are used to block or alter the color to fit the design. Black is used most often, and is made from iron oxide suspended in a gum solution to help it adhere to the glass. The artist also uses vinegar to make the oxide spread smoothly. Chemicals, such as silver nitrate which turns the glass gold, are also used. They try to avoid heavy use of any enamel because it can fade. The artist has a variety of brushes to achieve different textures and designs in the glass. After each layer is applied, a common hair dryer is used to dry that layer and then another is applied. After the glass is painted it is placed on trays to be fired in the kiln.
Trays of glass are put into a kiln and fired at 592 degrees Celsius, which is less than 1,200 degrees Fahrenheit. At this temperature the glass starts to lose its surface tension and the metal oxides sink into the surface of the glass. The oxides and the glass become fused and the oxide is in the glass permanently. Depending on the texture of the glass, often times the artist will paint all of the blacks on then they’ll fire the glass, then they’ll paint all of the half tones on the glass and then fire it, and then they will paint the silver nitrates on the glass and fire it again. Certain pieces may be painted and fired several times. Usually after one or two kiln fires all of the desired textures are in the glass. After the glass has been fired it is ready to be glazed (leaded).
The initial pattern is secured to the glazing table and the glazer begins by measuring and cutting each piece of glass and each lead and putting the two together. The lead is soft and bendable and ranges in size from 3/16 to 1 1/8 inches. Some windows may have multiple lead sizes. The lead has an H-shape, so each piece of glass is surrounded entirely. Lead scraps are recycled and new lead is stretched and straightened before it is used. Once the window is plated, the perimeter lead is applied and all of the joints are swabbed with oil and then soldered together with a lead-tin alloy on both sides of the window. The glazer must make sure the windows is the correct size for the frame and also that the artist’s designs match up accurately.
The windows are either lowered or carried down to the cement room where putties are rubbed underneath the leads in is a waterproofing process. The putty prevents the pieces from moving around. Then a glazing knife is used to turn down all of the leads around the glass and the perimeter. Marble dust is then applied to take up any of the leftover putty and is removed with a soft brush. Next, a wire brush is used to shine the leads and the glass is polished to remove the oil left from the putty. This procedure is repeated on both sides of the window and is very messy, which makes removing the putty and polishing the glass very time-consuming. Once the window is clean it is brought back upstairs to begin the reinforcing part of the process.
The windows are reinforced with steel bars coated in zinc, because the lead used in the glazing process is too soft to support the window by itself. The artists determine where the bars need to be strategically placed to ensure they will not only support the window, but also not obscure the design. Once the bars are placed, an in-house mixture of acid is applied to each spot where the bar crosses the lead and then an electric iron is used to solder the joints. The acid helps the solder adhere to both the bar and the lead. The bars are only applied to inside of the window and when finished window cleaner is applied to neutralize the acid. If the acid is not neutralized it will dissolve the lead over time. This process completes the window and it is then ready to be shipped.
The Frei Co. normally packs and drives its own trucks to the work site. The windows stack “almost like the old fashion vinyl records” and one truck can hold over an acre of glass. Their trucks are very dense and are packed by those with years of experience. The windows are anywhere from 1/8 to 3/16 of an inch thick and so they don’t take up much room, but they are carefully packed around with Styrofoam and other packing material so every section has a cushion. This method ensures that the windows arrive at the church with no cracks, but if there is one or if one cracks during installation, which is rare, it is quickly duplicated and sent back before the end of the installation. The windows are installed with special attention to wind and gravity loads.