New protective glazing could be fitted to four medieval windows in Lincoln Cathedral to protect the historic stained glass.
Special monitoring sensors will even be fitted to the windows to ensure the new glazing is set at exactly the right position to keep the medieval glass protected.
The project is planned for four of the lancet windows beneath the Bishop’s Eye which date from the 13th century.
The new scheme, if agreed by the cathedral’s Glazing Advisory Committee, will start early next year when the old glass is going to be removed for conservation.
New, specially made, protective glass will then be fitted to the window’s exterior recess before the conserved windows are rehung behind it on special brackets.
The new protective glazing will then shield the stained glass from the elements – particularly important in Lincoln because the cathedral is more exposed than most.
The project is likely to cost £550,000.
However the air flow and condensation between the sheets must be exactly right to prevent any damage to the medieval glass.
So sensors will be fitted between the two windows and the measurements automatically sent to a specialist company in Cambridge where they will be monitored for a year.
That will allow the works department to adjust the distance between the two windows to the exact millimetre needed.
It is only the second time the Cathedral will have protective glazing fitted in recent years.
In 2006 the Dean’s Eye had special protective glass fitted with the electronic monitoring only finishing last year.
Each of the four windows needs to be measured and monitored individually because they are all slightly different sizes so the entire project will take four years to complete.
“It is a long and very detailed process but it will ensure this priceless medieval glass is protected from the elements,” said works department manager Carol Heidschuster.
“Each window needs to be accurately assessed for humidity, air flow and temperature and monitored for a year so we can ensure the windows are placed at exactly the right distance from one another.
“Most visitors view the stained glass from the inside with the light travelling through it and we specially design the outer panels to ensure the lead work patterns match those on the inside.
“So visitors will still be able to enjoy the splendour of the windows while they are being protected.”
The first window the Lincoln Glazing Department will be conserving is the one damaged by a break-out in 2008 when an intruder used it to escape. The medallion depicted Moses in a biblical scene.