Can you spot the reproduced piece of painted glass?
Here at The Stonehouse, we often take a pile of neglected glass, and return it to its majestic glory. Sometimes, it takes a little magic to make that happen.
Sometimes that magic hits some speed bumps.
Let us start with the final piece. This unique and delicately painted window from England, cira 1880, was once a pair of windows. One window, perfectly intact, was kept as part of our private collection. A matching window was not so lucky. The lead on the second window had suffered corrosion, a few of the painted pieces were broken, and thus became a pile if gnarled lead came and glass, that was carefully stored away for a rainy day.
Our team of restoration artists set to work. The intact pieces were laid out, and the broken panes assessed. The original lead was observed, and rescued where possible to maintain as much of the original materials as possible.
Now, the hunt begins to match the colour and texture of the glass. Barely noticeable, the clear glass is actually a delicate shade of faintly tinted green. We have on premises, a vast library of modern and antique glass on hand for such occasions as replacing a small segment in our restorations.
When prospective matching glass is found, it is tested in various light to check compatibility to the original antique glass. First, on our artificial light table for a quick glance to test the texture, then in various natural light conditions, such as direct sunlight and diffused. The glass may seem not quite right in the artificial light, but a perfect match once the sun takes hold of the pigment.
Huzzah! We were lucky to have found the perfect match of colour and texture here in the shop!
However, we had a slight gut feeling that the glass would ‘strike’ in the kiln. “Striking” is when a glass changes colour at extreme temperatures. This is sometimes done on purpose by a manufacturer, for the use in fused glass art. But sometimes, especially with darker colours like deep blue, purples and reds, it is just a chemical reaction of pigments to heat. Since the glass would be fired in the kiln once painted, the found glass was at risk of striking. Extensive tests were done to check for the expected, and undesired results.
As expected, the glass did indeed strike. A small piece had pigment applied, and fired in the kiln. The pigment would have no affect on the striking of the glass, it would purely be the chemical reaction of the glass to the 1200°F heat of a kiln, the temperature required to fuse the paint to the glass.
Back to the hunt. We were able to find a perfect match of texture, but the colour was oh so slightly off in the quick glance of our artificial light. When held up to natural light, the colour difference was much less noticeable. A test was done in the kiln, and striking was adverted.
With the texture and colour now in hand, the next test was to match the pigments of both the dark scallop lines, and the silver stain.
First, we wanted to match the scallop lines colours as close as possible to the original. Most glass painting is done with a black stencil line, but these lines were done with a dark brown. The brown pigments come in a few different shades. The closest pigments were Umber and Bistre Browns. A sample of the pigments are kept on hand for matching, test done with a scale of opacity. Umber brown was found to be the best match, the bistre being too light of a shade.
Next came the matching of the silver stain.
Although the technique has been used in ancient drinking vessels in Egypt and Persia between 600-800 AD, silver stain was not introduced into medieval stained glass windows until the 1300’s. This groundbreaking discovery was a game changer for glass painters. Until silver stain, an artist was confined to using only a single colour of solid glass, and much creativity was used to monopolize the use of the single colour. Silver stain, allowed the artist to apply drops of colour to a single colour segment, enriching beautiful enhancements to portray embroidery, jewels, hair, wheat fields, and clothing.
An 8th century drinking vessel, from the Corning Museum of Glass
Above, yellow glass for use in the papal ferula (staff), and silver stain used to decorate the papal mitre (hat) from a 14th century French window, on display at Glencairn Museum, Bryn Athyn.
Silver stain is technically the only “stain” in stained glass. A “stained glass window” as you know it, is a design of coloured pot glass. Silver stain stains the glass by performing an ion exchange, soaking into the glass at about 1100°F, and thus, staining it.
Silver stain can be quite persnickety. Not enough heat, and the stain will not be able to transfer into the glass. Too much heat, and an unsavory dicloric effect (like oil on water) will ruin the glass.
High heat caused a oil like sheen on the glass.
A few tests were done on fragments of the intended glass, and fired along with the umber brown. Here, the test strip is show beside the original in artificial light.
More speed bumps!
There is a lot of experimenting that goes into glass painting, and one should learn to experiment on the side, not with the attempt of the final product. An experimental firing schedule, and application technique were attempted for the silver stain. The result came out too dark and blotchy. Luckily we still had a bit more glass in the stash to make another attempt. A different shade was attempted, and VOILA!
All the hard work paid off in the end. The result is a seamless restoration of this 1880’s stained glass masterpiece, along with the learning curve of matching glass, textures, silver stain and pigments. Thank you for joining us on the journey of our work. If you have any questions, we would love to hear from you.
The Stonehouse of Campbellville is both a retail store selling leaded antique stained glass windows, and a stained glass studio with an on-site interpretive centre. With over 3,000+ windows in the summer and 2,000+ windows in the winter, we are quite possibly the world’s largest dealer in antique stained glass, carrying both secular and religious windows.
We are open every day from 9-5, except Christmas Day.
8565 Guelph Line, Campbellville, ON L0P 1B0