Part of Historic Environment Scotland

Historic Glass and Glazing Conservation

Dates: 27/03/19
Days of the week: Tuesday, Wednesday
Total hours: 51
Taught hours: 22.5
On-site instruction: 10.5
Off-site instruction: 12


Delve into a range of issues to do with the manufacture, use and conservation of glass and glazing systems in Scotland’s historic built environment.

Develop your understanding of the physical nature of glass, its significance to the historic building, and how it interacts with its support structures. Both plain and decorative glass are examined, with particular attention paid to the use of stained, painted and etched glass in church and cathedral settings. A look at the history of glass production in Scotland is followed by a basic overview of the science of glass manufacture.

Conservation repair principles, methods and techniques form the core of this module. You will find out how to plan suitable conservation and repair strategies for historic glass, and study each stage involved in a repair project. Central to the specification element of the process is learning how to conduct archival research. This can help you to identify the artist, craftsperson or studio responsible for the original glasswork.

A strong emphasis is placed on the importance of planned maintenance, given the fragility of historic glass. Technological advances in safety, structural and thermal glazing products are also considered, particularly in relation to retrofitting, upgrading or altering traditional buildings.

Entry requirements

Individual modules are open to anyone with an interest in the subject matter. Applicants for the Advanced Professional Diploma should have a relevant degree or professional experience.

Classes, lectures and presentations

  • History of Architectural Glass
  • Historic Glazing
  • Glazing – Site Work and Good Practice
  • Stained, Painted and Etched Glass
  • Decay and Conservation of Decorative Glass
  • Specifying Repairs to Decorative Glass
  • Glass and Glazing – Site Work/Health and Safety

Potential site visits

  • Lansdowne Church, Glasgow
  • Maryhill Burgh Halls, Glasgow
  • Ramshorn Church, Glasgow
  • Glasgow Cathedral
  • Scottish National War Memorial and St Margaret’s Chapel, Edinburgh Castle
  • Old Greyfriars Church, Edinburgh
  • St John the Evangelist, Edinburgh
  • Rosslyn Chapel
  • Newhailes House, Musselburgh
  • St Machar’s Cathedral, Aberdeen
  • Paisley Abbey
  • Edinburgh New Town
  • Decorative glass restorers' workshops


Plain glazing

  • Value of historic glass
  • Glassmaking process – technological development, Scottish historical context
  • Types of window glass – e.g. broad, muff or cylinder, crown, cast drawn sheet, plate, rolled, float, patterned, textured
  • Characteristics and properties – e.g. colouring, textures, size
  • Range of uses – early leaded panes, clear glazing in timber sashes, and Vitriolite, glass blocks and other decorative and structural glasses

Decay of plain glazing

  • Cracking and fracturing – e.g. settlement, impact damage, racking of timber frame, vibration or thermal movement
  • Chemical change, corrosion, breakdown or surface damage
  • Abrasion or discolouration
  • Repairs and replacement – determining the cause of damage or deterioration, significance of historic glass vs need for energy efficiency
  • Specifying repair works – including maintenance regimes for glazing systems
  • Sourcing replacement glass – sustainability, alternative materials, current regulations and standards, use of double glazed units

Stained, painted and etched glass

  • Technological development and Scottish decorative glass traditions
  • Types of glass used – e.g. antique, cathedral, quarry, slab
  • Types of colouring – e.g. pot metal, flashed, stained
  • Paint and paint types – e.g. grisailles, stains, enamels, pigments and fluxes
  • Historical sourcing – e.g. English, German
  • Material characteristics – e.g. resistance to weathering, general strengths and weaknesses
  • Production of decorative glass – e.g. acids and sand etching, firing process, patterns and textures, plating
  • Range of glazing uses – e.g. exterior walls, within interiors, doors, panelling

Decay of decorative glass

  • Determining the cause of damage or deterioration
  • Lack of support – e.g. failure of lead cames, iron saddle bars, iron frames
  • Chemical breakdown, natural faults, annealing cracks
  • Loss of paint or colour, fading, surface scratches
  • Decay of putty
  • Organic growth, acids and air pollution
  • External stresses – e.g. impact damage, subsidence of masonry, vandalism, fire damage, condensation, vibration or thermal movement
  • Failure or inadequacy of past repairs
  • Advantages and disadvantages of UV filters and films to protect interiors or for health and safety purposes

Specifying repairs to decorative glass

  • Sourcing conservators and craftsmen
  • Determine need and approach – in situ vs workshop repairs, and preservation, restoration or replacement
  • Reversibility of repairs – e.g. copper foil, adhesives and epoxies, repainting and replication of glass
  • Flattening bowed or sagging window panels
  • Renewing of lead cames, T-bars, saddle bars, copper ties and other supports
  • Glass repairs using adhesives
  • Installation of backing plates
  • Sourcing suitable glass for replacement
  • Consolidation of fragile paint
  • Cleaning – preserving patina, removal of soiling, chemical vs mechanical processes
  • Repair or renewal of lead cames and putty
  • Improving thermal performance of glazing system
  • UV, pollution and vandalism protection, need for ventilation, public safety
  • Site practice – from survey, specification and work sequence to maintenance regimes that limit potential damage to historic fabric
  • Health and safety issues – e.g. toxicity (lead, adhesives), use of acids for etching, removal of glass shards, soldering risks, working at height