All that glitters
© Period Living
Historic glass sparkles like diamonds and its beautiful imperfections can pack your period home with personality. If you’ve got it, read on to discover ways of keeping it healthy and the best mothods for coaxing damaged areas back to life . . .
The imperfections within old glass can twist and scatter the light like an exquisite, constantly changing kaleidoscope. Scenes of cloudy, snowy or sunny weather can seem magical from inside your room, and the twinkling, shimmering reflections seen from outside can never be replicated by modern, flawless fenestration. Ancient glass was handmade and has a living quality, due to irregularities such as tiny bubbles (seeds) and ripples (reams), often accompanied by a tinge of yellow, purple or green. Never believe anyone who tells you that handmade glass is no longer available: it is still being made by glassmakers in the original way both here and abroad, and there are several specialist dealers who can match most types for you (see below). It really is worth paying the extra to have your period home’s crowning glory looking authentic. And there is a number of talented stained-glass artists who can create a painted glass panel to an individual design, so why not have your own coat of arms over the front door?

The material has always been made by heating sand, silica, soda and lime together until it’s a treacly liquid, then manipulating this into shape until it cools and solidifies. ‘Gentilhommes verriers’ from France made window glass here in 1567 by the ‘Blown cylinder method’ - known as the ‘Broad glass’ process. A blowpipe was pushed into the molten mix and a glass cylinder blown, which was stretched to a sausage shape, cut open and flattened out. Sheets were of limited size, slightly wavy, uneven and discoloured quickly, and 16 and 17th century glass was sometimes lightly tinted (often pale yellow) because of impurities in the sand, and also contained seeds and reams. Crown Glass (1696 - 1872) was made by opening out a blown bubble of glass attached to an iron pipe (punty), allowing centrifugal force to form a flat circle up to 48” and later even 60”, in diameter; this was then cut into smaller pieces which often show the circular pattern, but its central part (bullion), where the punty was attached, was usually thrown away. Early in its development, glass could only be produced in small panes, hence the use of ‘leaded lights’ (see below) for building up window-size panels. ‘Cast plate’ glass (1688 - 1923) was originally used for mirrors and coach windows: molten glass was poured onto an iron table and rolled into a thick flat plate, then put into an annealing kiln for ten days; finally it was ground and polished to a perfect finish. ‘Cylinder blown’ sheet glass was again manufactured in the 1850s, a reversion to the original method, the difference being that larger pieces could now be made. At the beginning of the 20th century the technology arrived for making machine-manufactured glass, culminating in today’s flawless ‘float’ glass.

Stained glass is the term applied to glazing, often coloured in its manufacture, which is then hand-painted using oxides or enamels, then kiln-fired so that it fuses into the glass. ‘Stained’ refers to the characteristic silver stains producing tones from pale lemon to deep amber, usually applied to the reverse face and fired in. “Typically you might see hand-painted leaded lights in the bay windows of 1930s to 1950s houses,” says Drew Pritchard, glass expert and director of Drew Pritchard Stained Glass and Architectural Antiques, recently featured in BBC2’s ‘The Reclaimers’ programmes. “Often these would have a sun or a star in their centre.”
Acid-etched glass is where flash fired mouth-blown glass has a colour fused onto it. Acid is brushed over specific surface areas to selectively remove layers of colour, as a painting in reverse. Sand-blasting can give textured effects.
The craft of stained glass painting is still very much alive, and if you want to commission your own design contact the British Society of Master Glass Painters (BSMGP) for an artist in your area. Before making the actual piece, the artist creates a detailed life-sized blueprint (cartoon) showing colours and lead-came detailing.

Small diamond- or rectangular-shaped panes of glass (quarries), either plain or painted , were joined by strips of lead (caming) so as to unite them into a larger panel. The lead is H-shaped in cross section, the lips enclosing glass edges. Quarries were bonded into the lead slot with cement (whiting, lamp black and linseed oil). The cames were then soldered with lead from both sides.
Keith Hill, co-director of The Stained Glass Workshop, says, “For leaded-light work the thinner the glass the better, because thinness allows the use of a narrow lead came ‘heart’ - that is the width of slot - requiring less cement and being consequently lighter than standard-heart lead-camed work. As a solution to leaking windows you can use leaded-light cement to fill any gaps, but this is only temporary, as the remnants of the failed original putty will be inside, preventing sufficient penetration of the replacement material. Check for cracked soldered joints and leadwork, or for bowing and buckling - for instance pieces of glass starting to protrude from the lead.”
Ben Sinclair, director or Norgrove Studios, adds, “Crook your finger and tap the quarry. It should sounds like a drum, but a looseness or rattle indicates that the window may need to be reconstructed. A specialist can peel back the lead and replace odd quarries on site, but a complete rebuild has to be done in the studio.”
“To clean leaded lights, sweep them with a dry paint brush,” continues Ben, “simultaneously sucking up detritus with a vacuum cleaner - do not use a chamois leather on it, this can put pressure on the glazing. Never use proprietary window cleaning fluids, but an alcohol-based specialist cleaner, such as Hodgsons Sealants’ ‘glass cleaner’. Leave the leaded parts alone: grey-black lead oxide forms on its surface, creating an attractive patination of age.”
Drew suggests, “Think of it like cleaning a pair of shoes. Remove grease from the glass with old shoe brush, newspaper, or lint-free cloth - continuous brush polishing will give them a shine. Lemon juice or vinegar are good for cleaning, and you can also rub the glass on both sides with fine grade (00) oil-free wire wool.”

Companies here and in Europe now make glass in the old ways for restoration work. Some has a slightly bowed surface (for Crown glass), while other glasses possess apparent flaws. “The English Antique Glass Company are producing some really fabulous glasses, which are absolutely ideal if you’re trying to replicate a decorative glass of the late 19th early 20th Century,” says Ben. “They can also match up earlier glasses, reproducing the same colours and faults.”
Mike Tuffy, furnace engineer, glass expert and director of English Antique Glass, explains, “We make glass to order, mainly for restoration work. Recently someone chose some of our clear glass to match their 17th century cottage, but we explained it would never originally have been as clear, so we gave it a faint green tint. We do this by adding a coloured glass ‘fritz’ - that’s crushed granules of glass - into the molten mixture. We’ve got three shades of green, several of amber or brown and some purples. We can also introduce a ‘cord’ by adding glass of a slightly different composition that doesn’t quite melt in, creating stripes like ropes. To get authentic seeding, we’ll put a potato into the glass and boil it up - the moisture evaporates quickly and stirs up all the muck from the bottom of the furnace and creates a lot of bubbles that gradually clears to leave just a few seeds here and there.”
Mike’s company is the only maker of handmade glass in the UK, but several glass dealers import hand blown glass from Europe and they also offer a matching service (see below).