created by Carl Sabanski
Stained Glass Sundial
Stained Glass Sundial: a (generally vertical) dial in which the dial face is of stained glass, and is viewed from the back, i.e. through the glass from inside the building. The gnomon remains on the outside of the building, and frequently causes cracking of the glass if supported directly from it. Typically, they were incorporated into church windows in the 17th century, although most are now in museums and there are some notable modern examples.
Figure 1 illustrates a vertical direct south sundial and the position of the gnomon on the face of the dial.
Figure 1: Vertical Direct South Sundial (ZW2000/CAD)
The layout for a vertical direct south stained glass sundial would appear as shown in Figure 2. This is how Figure 1 would appear if it were viewed from behind as though it were a window. It is a mirror image of Figure 1. The gnomon, however, is still positioned as shown in Figure 1 and would be located outside the window. The gnomon's shadow falls on the back face of the dial and is seen from the front through the glass. The glass chosen must be transparent enough that the shadow is visible.
There are two methods that can be used to create a stained glass sundial. The first is the traditional lead came method. This uses preformed strips of lead that come in a variety of profiles and sizes. For example an "H" shaped came can accept glass on both sides while a "U" came only from one side. The glass is cut from patterns and then placed in a framework of lead came. The joints are then soldered and the entire piece is cemented to secure all the glass pieces within the lead came and to waterproof it. The second is the copper foil method. This method uses very thin adhesive backed copper foil that is available in a variety of widths. Each piece of glass is completely wrapped with copper foil that is folded over on the top and bottom of the glass. The pieces are then soldered together along all the joints using a rounded solder seam.
Both methods of doing stained glass are fun. With the copper foil method smaller pieces of glass can be used and more intricate patterns can be created. In both cases pieces of glass can be painted to include details that cannot be had with glass alone. This is evident in many church windows. The best way to learn is to take lessons from a stained glass supplier. They can provide all the tools required and more varieties and colours of glass then you can imagine. And you don't just have to make sundials. There are pattern books galore that will give you a never ending supply of ideas.
Figure 3 shows a stained glass sundial made from the layout shown in Figure 2. The dial is shown from the inside. The gnomon is visible at the back of the dial.
The attachment of the gnomon requires some attention. If the gnomon is attached directly to the sundial care must be taken that it does not stress the glass and ultimately cause it to break. There are methods of reinforcing both lead came and copper foil stained glass pieces. Perhaps a metal medallion located at the dial's origin secured to a number of glass pieces around it might distribute the stresses. The gnomon could also be supported with struts from the side of the window or from other points within the sundial. In any case, a stained glass sundial with an integral gnomon will have to placed outside any window space it will occupy.
If the dial is to be mounted inside an existing window the gnomon will be mounted outside. This creates its own issues as the gnomon must not be mounted at a point directly perpendicular to the dial's origin. The gnomon will be positioned below the origin so that when its style is projected through the window it will intersect the origin. The mounting position will depend on how thick the window is.
Stained glass can be used to create other types of sundials, a horizontal sundial for example.
There is a little trick that can be used to simplify the design of a stained glass sundial. Refer to Figure 4 for this description. The vertical declining sundial at the top left is designed for the Northern Hemisphere. As you are looking at the back of this sundial when it is made of stained glass a mirror image must be created. This is shown at the top right. Now look at the sundial at the bottom right. This is the same sundial but designed for the Southern Hemisphere. It is identical to the mirror imaged sundial.
So to make the design of a stained glass sundial very simple just design the sundial for the Hemisphere that you don't live in. It's just that easy.