Designing the Sundial Face Pattern
Gnomon Design and Attachment
Sundial Pattern Testing
Materials and Tools
Glass Joining Techniques
Mosaic and Ceramic Sundial Assembly Methods
Glossaries for Sundials and Stained Glass
Except for the hard metals used in making the gnomon and some types of glass, the glass artisans are free to use the same materials they normally use in their windows. Compared to most hobbies, stained glass assembly is inexpensive as only a few simple tools are required. Sundial designers can use their favorite design tools and computer programs.
Glass: The glass can be stained, etched or painted or a combination of these. The type of glass you select for the sundial face is very important. On that part of the sundial face where you need to see the gnomon's shadow to tell time do not use clear transparent glass or glass that is stained too darkly, otherwise the shadow won't be visible. The glass must be opaque. The best glass that shows the shadow is called "opal" or "opalescent" glass. It has an additive that causes a little crystallization to occur and this increases light reflection and produces a milky white color if no pigments are added. Opalescent glass comes in solid colors or in mixed colors (variegated). Both work well. Also, do not use highly textured glass with a lot of waves or surface texture because the uneven surface will distort the shadow shape. Almost all stained glass sold in world is approximately 1/8" thick (3.2 mm). In the US, it is usually available in sheets of 24 x 48 inches (61 x 122 cm). It weighs about 1.6 lbs./sq. ft. (7.76 K/sq. M).
Gnomon: You should make the gnomon (the shadow caster) from metals like brass, bronze or stainless steel. You might use an aluminum rod or hollow metal tube if gnomon weight is an issue. If attaching a metal sheet or sphere to a rod, you can silver solder or use a modern adhesive.
1. Lead Came: The old traditional lead came method uses extruded or milled lead strips that are channeled into an 'H' or 'U' shape into which are inserted two adjoining glass pieces. The pieces are soldered at the joints and cemented in place. The lead came holds the pieces together and after cementing, gives structural strength to the window. It comes in rolls or strips of different widths.
2. Zinc Came: Zinc is much stronger, lighter and more rigid than lead. Use zinc came by itself or in addition to lead came to strengthen the glass panel structure. 'U'-shaped zinc came is a good and strong window edge border frame but you also can use 'H'-shaped zinc came for internal bracing. Zinc won't bend as well as lead in very tight curves.
3. Brass Came: Structurally strong like zinc came, brass came makes an attractive brass border and it comes in 'U' channels also. To touch up solder joints, use a gold marker pen.
4. Copper Came: Structurally strong like zinc and brass came, but bends easier than brass.
Reinforcing Bar: Large windows need reinforcing of some kind, whether it's brass or zinc came or reinforcing bars. Reinforcing bars are zinc coated 1/8" thick steel bar usually about 1/2" or 3/4" wide soldered on edge in several places to the lead came face, usually on the interior side. Usually only a few are needed at the weak points only. They are necessary in large windows bigger than about 6 square feet, especially those that are exposed to the heat of the sun because heat will cause the window to bow or sag.
Paints and Stains: Special paints called vitreous paints or glass paints have been developed for painting glass. There are also special vitreous stains called silver stains. The paints are mixtures of finely ground clear lead glass (frit) and pigments or metallic oxides for coloring. You must use glass frit that has the same Coefficient Of Expansion (COE) as the glass on which it's painted, otherwise it will not fuse properly. Sold in powdered form, you mix the frit and colors with a mixing agent such as water, white vinegar, turpentine or oil and an adhesive agent like gum arabic or sugar. Glass Paints have melting points (1250° - 1400° F) that are lower than the glass (1500° - 2000° F). In a kiln, the paint becomes fluid and permanently fuses to the glass when the glass starts to soften.
There are two types of vitreous paints: Enamels and Glass Stainers' Colors. Enamels are transparent and come in many bright colors but they do not adhere to the glass as well as the glass stainers' colors. Glass Stainers' Colors are the most important paints for glass painting and are sometimes mistakenly called stains. They are opaque and not transparent and are only available in limited colors of blacks, browns, gray-greens, flesh reds, and obscuring white. They are used for tracing and matting (shading).
Silver Stain has been used for centuries and is made from gamboge gum and silver nitrate and produces yellow to light orange transparent colors in the glass surface. It is not the color of silver after firing! This was a very popular coloring material in old stained glass sundials.
There are other oil and water based glass paints that air dry without a kiln at room or kitchen oven temperatures. But these paints are not as durable as kiln enamel and can wear off because the paint does not fuse with the glass. If you use these common paints, it would be wise to rough up the glass surface before applying paint so that they will adhere better.
Patina Chemicals: You can purchase liquid chemicals that will change the color of the raw shiny grey lead or zinc came and the solder. After window assembly, you brush the chemical onto the metal and solder and allow it to react with the metal. The patina chemicals are different for lead and zinc and are available in black or copper colors.
Glass Tools: The following tools are considered to be essential: a pattern template (2 copies), pattern paper (Mylar, velum or bond), carbon paper, pencil, glue stick, 3/4" masking tape, black and silver fine point Sharpee pens, utility/stencil knife, 3-bladed pattern scissors, regular scissors, cork-backed ruler, glass square, glass cutter, lead shears, grozing pliers, running pliers, wood or plastic fid, safety glasses, particle board or plywood work board, farrier nails (like horseshoe nails), glazing hammer, metal came or copper foil, glass, flux, flux brush, 60/40 solder, old sponge, soldering iron, rheostat, sal ammoniac, wire brush, flux remover, cement kit (includes oil, putty brush, whiting, orange stick, and 0000steel wool, rubber gloves, old towels, newspapers). The only expensive tool required is a glass grinder with a spinning diamond wheel used for shaping and smoothing jagged glass edges. A good one costs about $200 US.