Melissa Sieling has been snapping photos of her progress and here are a few more. This is where things get a good bit more interesting.
In our last posting, we explained the selection of the hand blown glasses and how important that process was to the interpretation of the design. While Melissa is selecting glass, another craftsman is hand-cutting what she has selected. This is done by hand, using a garden variety glass cutter, the same as you might purchase in a hardware store. To be sure, there is a great deal of skill involved. Some day soon I hope to produce a few videos on the subject of glass cutting but for now, let me explain the tenants of this craft. Each piece of glass will be hand cut, using the patterns made for this window. When the exact location within a sheet of glass is chosen, the pattern is placed on top of the glass and the profile or outline of the pattern is “scored” into the surface of the sheet of glass. Note that the glass cutter does not actually cut the glass. A tiny wheel of hardened steel at the end of the glass cutting tool is run along the perimeter of the pattern, impressing a line into the surface of the glass. This score will cause the glass to break along the course of this line. We cause the break to occur in several ways. Sometimes we will snap the pieces apart by applying pressure on either side of the line. Other times, we will tap the glass sharply along the underside of the line, producing the vibrations that will cause the glass to break along the line. This is a fun part of the practice but it can be frustrating because the glass can seem to have a mind of its own. Straight lines are easy, complex curves require much skill and practice.The hands belong to Simon Grigsby. Note that three of the small patterns are taped down to the glass. This will ensure that they are cut out of exactly the desired part of the sheet. The hand-blown glass features lots of variation and some areas of a six-square-foot sheet can be lighter or darker. Here you can see a percentage of the glass for the window has been cut and the pieces are laid out over the B & W copy. Finally all the glass for the entire window is cut. This much cutting might have taken Simon about two days to complete. In amongst the photos was one of a band aid. Simon is the likely culprit for such a prank. We do go through our share of band aids but probably less than you might guess.
This photo shows an important part of the process that is acid etching. This is a technique I learned as an apprentice and I have always seen to it that my team knows how to do this safely. The best studios throughout history practiced this but probably only a few today would attempt it, owing to the danger involved. Hydrofloric acid has been used in conjunction with flashed glass to produce dramatic effects in windows. First, I must explain what flashed glass is. Most colored glass is colored throughout. This is called pot-metal glass. A quantity of metal (copper for instance) is added to the formula for glass and the glass is blown into cylinder and folded open into a sheet. For flashed glass, the glass blower gathers a quantity of clear glass onto the end of the blow-pipe. Before the glass is enlarged into a bubble, the clear is dipped into a vat of molten colored glass. So now we have a clear core with a thin layer of a color enveloping it. As the glass is blown larger and manipulated into a sheet, the result is a full sheet of glass that is clear but with a thin coating of a color on one surface. There are lots of different colors of flashed glass available. The most popular are reds and blues in varying degrees of density but there are many other colors available to us, even sheets that feature one color flashed over another, such as red on blue. The thin layer of color will produce shading in the colors as the flash changes in thickness but what is even more interesting is that we can use acid to etch away the color to reveal the clear glass underneath. In the photo above, you can see the large dark piece of red flashed glass and across the top of this piece you can see that it has been covered with clear contact paper. Oddly enough, the plastic contact paper resists the acid and we use it to mask-off part of the sheet we want to remain unaltered. The surface of the pieces left exposed will be attacked with the acid. Over a period of hours, the red surface color will become lighter and lighter until (if we wish) the red disappears altogether, leaving that part of the piece clear. If you have ever admired the best Bavarian windows, they nearly all featured this technique, usually on Christ’s red robe. One can simply lighten an area to produce dramatic shading or an elaborate brocaded design can be shown in two colors. Often this method is combined with gold staining but we will leave that for another post. In the photo, the pieces of glass are resting with acid on the exposed surfaces. The small piece to the right has been etched completely-see the clear parts? Melissa is using this technique to produce the rays emitting from the dove. Where the rays pass through the red drapery (check the design in the first post) the drapery will be lighter, even more dramatically than in the watercolor. We suit-up for this, wearing eye protection, gloves, mask, etc. I am minus the fingerprint on one finger because I accidentally touched the bottle of acid with my fingertip nearly 30 years ago.
These last three shot show the beginning of the painting process. In the first, the border is being painted with fine linear design. She is painting with a long fine brush over a tracing paper cartoon of the border motif. All three photos show the glass laying on a light-box with the cartoon underneath the glass. Nearly all the surface of the window will be painted with linear work first, over the light box.
Vitreous glass paint consists of powdered iron oxide mixed with finely ground glass. The resulting pigment can be combined with various painting media to apply it to the glass. Finally when the painting is completed, the paint is fired into the glass. The 2nd and 3rd photos here show Melissa rendering the outline of the clouds, drapery and the feet of Christ. Note in this last photo how the red drapery appears lighter where the rays are passing through. This is the effects of the acid etching. Look for more later. I’ve got to get back to designing.