They like cooking at The Abbey Stained Glass in old Kilmainham. Not food but glass, stained glass. In two massive ovens, one a baker’s oven salvaged from Boland’s Mill, paint is fused on to glass at temperatures of 600 degrees Centigrade, firing up to five times to get the right depth, texture and colour, such is the precision demanded.

Anchored on easels in the workshop on the day of my visit are two magnificent stained glass windows from the Harry Clarke studios, which have just been restored for the Missionary Sisters of the Holy Rosary in Cavan.

Originally made in 1948 at a cost of £600, the price of a modest house, their restoration is the most recent example of work of this company, specialists in this centuries-old craft for 70 years.

Director Ken Ryan explains that the windows were removed and relocated to Cavan when the convent in Killeshandra closed down in 1985. The figures depicted include the Holy Spirit, St Paul and St Theresa, with Africans in the glass, a reference to the Sisters’ missionary work in Nigeria and elsewhere.

“Most of our work, 80 per cent of it, is for the church, although we also do domestic work, most recently restoring the 100-year-old leaded windows in a house in Terenure,” says Ryan.

On one table the leaded tracery on a Georgian fanlight for a house in Merrion Square is being remoulded and renewed. On another, four stained glass windows from a house in Inchicore will have another life, newly leaded, soldered and framed as door panels for a house in Meath.

Power of daylight

“The power of daylight is enormous,” says Ryan. “But stained glass will last for a thousand years provided you maintain it. Dark colours attract light and heat from the sun and over time the lead begins to sag, the windows start to buckle and twist and the glass starts to crack and break.”

That necessitates periodic restoration and great cathedrals such as Chartres have the luxury of on-site studios with craftsmen and artists. Ireland has a wealth of stained glass due to an explosion of talent from the 1900s onwards, with Harry Clarke being its most outstanding and best known exponent.

The west of Ireland is particularly rich, according to Ryan, led by St Brendan’s Cathedral in Loughrea, an outstanding Celtic Revival masterwork and home to the greatest cross section of stained glass in the country.

Abbey has been responsible for its restoration and that of Clarke’s work all over Mayo and Galway, from Tuam to Ballinrobe, Cong, Newport, Claremorris and Kilmaine. “I suppose the reason for that would be people sending money back from America – it would make a great stained glass trail,” he says.

Lough Derg

One job he will never forget was the restoration of the Harry Clarke Stations of the Cross in Lough Derg, 14 windows which had to be transported by boat over half a mile of water in 1988.

Another project was the recovery and restoration of the huge stained glass window from 1859 by Michael O Connor in St James's Church in Dublin.

An explosion in the nearby brewery caused it to blow out of its frame and crash into pieces, a job that took Abbey’s artists and craftsmen months of work to complete.

The famous Evie Hone window My Four Green Fields, originally made for the World Fair in 1939, was restored 20 years ago for the Taoiseach's office when Charlie Haughey was in power.

“My late father Frank worked all his life in stained glass and used to go to America every two years to keep us going,” recalls Ryan, who trained as a quantity surveyor and worked in Africa in the building trade before joining his father in 1980.

William Malone, a fourth generation craftsman, whose grandfather worked in the Harry Clarke studios, carries on the tradition.

Coloured glass

The premises has racks of stained and etched glass. Long wooden tables allow for the cutting, leading and cementing of coloured glass, both for new and old pieces.

Artist Brendan Mullins shows the colourful graphic effects of plating and etching two pieces of glass. Elsewhere Ryan shows how glass is hand cut to match designs drawn on paper by glaziers – a procedure not without its hazards – before lead is applied, soldered and cemented to keep each piece in place.

Once described as a matchmaker between dispossessed stained glass and active churches, Ryan takes out stained glass and finds a use for it elsewhere.

“We never throw anything out,” he says. “We take windows from convents when they close down and we find good homes for them”.

He is particularly proud of the relocation of six Harry Clarke windows from the Sacred Heart Convent on Leeson Street, which he bought at an auction in Dublin 20 years ago.

“We were invited to install them temporarily in Cavan Cathedral and when they fitted perfectly, donors were found to finance their installation. They were designed and made in 1932, the same year as the Cathedral was built. It was as if they were made for it. It was miraculous.”