condition report and conservation ... - newton abbot museum · st. leonard’s church, wolborough...

Directors: Stephen Clare ACR, FMGP and Jack Clare Glaziers Yard, Lovers Walk, Somerset, BA5 2QL holywellglass.com |[email protected] T: 01749 671061

Condition Report and conservation Proposal: St. Leonard’s Church, Wolborough St, Newton Abbot 30th November 2017. As requested, we surveyed all of the stained glass to the church, which is limited to a large east chancel window, two, 2 light windows to the south chancel, and fragmentary remains of the original early 19th century glazing scheme to the traceries of the three west elevation windows. As part of the planning stage for the new usage of the building, the parish and town Council has thoroughly researched the history of the building, including the stained glass, with particular emphasis on the involvement of Frederick Drake.

West elevation and CVMA annotated floor plan


Context: St. Leonards is listed Grade II, and was built to replace the 15th century church, which was demolished apart from the tower in 1836. The church dates from 1835, and was designed by Richard Millward, extensive alterations were carried out circa 1876 by J.W. Rowell. The main church nave has 5 windows each side, there are three windows to the chancel, and three windows to the west front overlooking Wolborough Street. The nave has a gallery, which bisects the north and south elevation windows.

Interior looking east and southwest corner- 1896. Images Copyright Francis Frith collection


The chancel windows At ground level to the chancel south elevation (windows sII, sIII) are four lights by Frederick Drake, an accomplished local stained glass artist of the late 19th century. The subjects are for sII the Adoration of the Magi and Presentation at the Temple, and for sIII Christ in the Temple, and the Wedding at Cana. (Main lights each approximately 460 x 1220mm). There is a single quatrefoil tracery to each window with angels holding banners, which have great charm.

Windows sII and sIII

The windows are very well executed, in glass paint and silver stain, with crisp line work and half tone, which is well fired and in good condition. The lead work- predominantly ¼ inch round section is in good order, as is the stained glass cement. Each window has internal tie bars, two per light with copper ties, which remain intact. The perimeter mortar is hard Portland cement based, and remains in good condition.


The East Chancel window

East Chancel window.

The east chancel window comprises three lights with scenes from the life of Christ. The left hand light has the Nativity, the centre light a crucifixion above the Supper at Emmaus, and the right hand light the Resurrection. The window has trefoil traceries with angels holding banners. It is possible that the central light with the Crucifixion was commissioned first and completed at the opening of the re-modelled church in 1877. The side- lights, and perhaps base section of the central light was completed at a later date as funds allowed. There is a slight stylistic difference between the scenes, which supports this. The archive image above demonstrates that the entire window was in place by 1896. It was not possible to closely examine the east chancel window due to its height, although access will be provided as scaffolding is provided as further surveying progresses. However examination with binoculars suggests that the window, in common with the other Drake windows survives in good condition. It is therefore proposed that the stained glass by Drake does not require any conservation/restoration at present. The west façade windows: nVI, WI, and sIX: The diamond quarry plain glazing to the west windows has been replaced over the centuries with double rolled cathedral glass of various types, probably during the late 19th/early 20th centuries. This survives in reasonable condition, but its restoration/conservation needs are not considered as part of this report. The surviving early 19th century glass in the traceries of all three windows is an extremely important survival of the period, much of our heritage of this period has been discarded over time as it fell out of fashion and favour. It is therefore essential that this glass, although seemingly insignificant is valued and conserved. In our recommendations for the glass, we have taken note of the wholly unsympathetic earlier restoration work, and have recommended some restoration as well as conservation in its treatment, which is appropriate in this particular case.


Window nVI

In the three traceries only are remains of early 19th C glazing, which appears to be in its original lead; although the fine lead is disrupted by clumsy earlier repairs. There is a central quatrefoil tracery, which has a very finely painted central section in paint and silver stain set on a ground of couverte enamel quarries, which is original. The right hand lobe has a lovely delicate circular device with blue enamel in the centre, with a slender band of ruby stain, and a fleuron of paint and silver stain in the outer area. This is original and undamaged. The borders in intense green and red are also original. The left hand lobe may have a ghost image of original painted detail, it is very difficult to determine from the ground. The upper and lower lobes are infilled with unsightly double rolled cathedral glass. The eyelets have original truncated roundels in red and green glass on a ground of couverte enamel. These are original and intact. Projected works: Remove the central quatrefoil only, and install temporary glazing. Reproduce the original glass in the right hand lobe for the missing three sections. (If the left hand roundel does prove to contain original glass, it may be appropriate to re enforce painted detail on a backing glass). See detailed specification for work. Re lead employing slender sections closely matching the original, but conserve any original surviving lead. Re fix into lime mortar. Clean the two eyelets in situ employing de- ionised water on swabs. Budget costs for works detailed £1,800 plus VAT.


Window sIX

In the three traceries only are remains of early 19th C glazing, which appears to be in its original lead; although the fine lead is disrupted by clumsy earlier repairs. There is a central geometric device, set on a ground of couverte enamel, which is original. The right hand lobe has a lovely circular device with blue enamel in the centre, with a fleuron in two colours of silver stain, and outer band of ruby stain. This is original and undamaged. The left hand lobe has a similar fleuron, beautifully detailed and original. The lower lobe has a delightful wheel device, with graded red and silver stain, and a border of couverte enamel. The upper lobe is infilled with unsightly yellow double rolled cathedral glass. The eyelets have original truncated roundels in red and green glass on a ground of couverte enamel. These are original and intact. Projected works: Remove the central quatrefoil only, and install temporary glazing. Reproduce the original glass in the lower lobe for the missing upper section. See detailed specification for work. Re lead employing slender sections closely matching the original, but conserve any original surviving lead. Re fix into lime mortar. Clean the two eyelets in situ employing de- ionised water on swabs. Budget cost for works approximately £ 1,240 plus VAT.


Window WI (East window).


Three large traceries and eleven eyelets survive. The large central octfoil has vivid purple borders and a ground of couverte enamel quarries, all of which is original. In the centre is a magnificent heraldic device with the arms of Courtney. An Earl’s coronet in silver stain and red stain surmounts a shield with red enamel torteaux quartered with blue enamel lions rampant. At the base on a ground of couverte, the motto ‘QUOD VERUM TUTUM’. This is intact, with well fired painted detail, and blue enamel in good order, but has crude early repair leads, which mar the delicacy of the shield. The lead work is also weakened and bowed, with thin copper ties parted from supporting tie bars, which are ferrous, and form a slender supporting armature- almost certainly original. There is no visible deterioration of the glass, which retains an excellent fire finish. The two large quatrefoil traceries have purple crosses on a ground of couverte enamel. These appear to have original lead work. They are in reasonable condition, and can be conserved in –situ. The eyelets have truncated roundels in yellow and blue glass. Two outer dagger eyelets have fantastic complex chequer pattern in blue, ruby, and white glass. All of the eyelets are in fair condition, and can be conserved in-situ. Projected works: Remove the central quatrefoil only, and install temporary glazing. Carefully dismantle to allow access to the central shield. Carry out resin bond repairs to the four damaged sections, and provide with supporting thermoformed backing glasses. The central section should then be set slightly inside the original position, tied and soldered to the original supporting armature. In its place very slightly matted cylinder glass, leaded to the primary lead lines should be leaded into the panel. This is not to protect painted detail or glass, which is in good condition, but to protect resin bonded sections from wind-flex. Re lead employing slender sections closely matching the original, but strictly conserve any original surviving lead. A new perimeter lead may be advisable to give the panel support. Re fix panel into lime mortar. Clean the eyelets in situ employing de- ionised water on swabs. Budget cost for works approximately £ 2,450 plus VAT. Detailed Specification for Works: • Carefully remove stained glass panels by chipping away perimeter mortar with

tungsten tipped chisel. • Cut copper ties and free the stained glass panel from the opening. • Install temporary glazing using twin wall polycarbonate sheet firmly supported on

timber battens. • Pack panels in inert materials prior to transportation to workshop. • Prepare three careful rubbings from the lead matrix. Use one rubbing to lay out

glass when dismantled, the second rubbing as a guide for re leading and the third for conservation record annotation with Church Building Council (CBC) conservation symbols.

• Prepare photographic record before, during and after conservation/restoration works.


• Prepare a pre-conservation proposal document for each panel for the information of the client in line with best practice: in consultation with the client, their agent or statutory bodies as appropriate.

• Carefully dismantle the glass from the lead as necessary. Presume in favour of conservation/retention of original lead whenever possible.

• Clean the glass employing wet or dry methods as appropriate following test cleaning monitored by binocular microscope. Method to be specified pre conservation document in consultation with the client or their agent. N.B Cleaning methods will be decided following careful evaluation on the light box with binocular and portable microscope. Advice will be sought from conservation scientists as appropriate. In line with best practice cleaning methods will not be specified in conservation reports prior to careful workshop examination.

• Repair broken pieces employing the copper foil method, silicone edge bonds (Silcoset 153), epoxy resin edge bonding (Araldite 2020) or string lead repair. Method to be specified in condition survey in consultation with the client or their agent.

• Missing areas to be replaced with painted kiln fired pieces closely matching the original. All new insertions to be clearly date marked in kiln fired glass paint.

• Re lead panel in section closely matching the original in section and heart depth. Leads to be custom milled as necessary. Proper reference should be given to the correct lead profile and depth and soldering technique appropriate to the window through close examination of existing lead types and historical reference.

• Weather proof the panel employing traditional stained glass cement or hand puttying dependent on the condition of the painted detail.

• Prepare full post conservation documentation to include written description of works, conservation diagram/s detailing interventions and photographic record.

• Re fix the panel on site into gauged lime mortar (Saint Astier FH3.5, sharp sand, 1:3). Visitor Interpretation As part of the project to develop the building as a community hub, and museum, it is intended to provide visitor interpretation in the form of poster boards or video loop. Holy Well Glass has a dedicated media coordinator, and wide experience in production of such material, and in offering support to clients in the production of such materials. We will be happy to assist with this element of the project.


Appendix 1. Description of common terminology/techniques. This description is simplistic, and intended merely to outline the techniques for the layman involved in commissioning the conservation of historic glass.

General

Stained glass usually consists of pieces of glass cut to a design, and painted with glass paint to apply detail such as drapery. The paint used is ground glass with iron oxide as a colourant. This detail is fired in a kiln at about 675° C, which fuses it to the surface of the glass.

The glass pieces are then built into panels into H-section lead “cames” soldered at every intersection. Finally the panels are weatherproofed with the application of stained glass cement; thinned linseed oil-based putty. This is traditionally applied with a bristle brush. Clearly if glass paint is frail, or if for instance medieval glass is pitted, and has been cleaned, more careful hand waterproofing should be specified.

Plain glazing or leaded lights have glass simply cut to shape and leaded into panels in the manner described above.

Glass

Is normally hand made, and of 2 types:

a) Cylinder glass - glass is blown into a cylinder shape, then cut along one side and opened in the furnace into a flat sheet.

b) Crown glass - a gather of molten glass is blown into a bubble, which is opened at one end and spun into a large disc. This is then cut into workable sheets, the central “bullion” being discarded.

These two types were in common usage from the Roman period onwards. Cylinder glass is still in production, crown glass is not.

*Note. Glass can be “flashed” - a thin layer or layers of one colour laid over another when molten. This allows the stained glass artist to employ abrading with a stone (in the medieval period) or later cutting through with acid to exploit the two or more colours.

Cutting the glass

The glass was cut in the medieval period by parting with a hot iron then nibbling or “grozing” the pieces to shape with a notched iron tool. The craftsmen achieved extraordinary results with these primitive means. A recognisable bevelled, worked edge is the hallmark of this early glass. Glass was cut with a diamond tool from the 16th. C. onwards, and is now commonly cut with a tungsten wheel.


Colour in glass

Is predominantly added to glass in the manufacture by the addition of metallic oxides to the molten glass. This is termed pot-metal glass.

The stained-glass craftsmen thus purchase coloured sheets from the glassmaker; the two disciplines have always been separate. The craftsman then cuts paints and leads the window, and fixes the completed panels in the window opening.

Applied decoration

Colour/tone can be applied and fired to surface of glass by the glass artist in 3 ways:

1. Glass paint, a mixture of ground glass and metallic oxide, which is kiln fired. When well fired this is extremely durable. There are many examples of 14th. C. glass painting in excellent condition. There can be problems with painted detail however. There were problems with under firing and incorrect glass paint recipes in the 19th. C. which means that today the paint both flakes off, and is badly affected by condensation. Glass paint from the 16th/17th. C. is frequently very soft in nature and needs very cautious handling. The conservation glazier needs to show the knowledge and sensitivity to identify glass paint condition and deal with such problems.

2. By the application of silver-stain to chemically colour the glass when fired in the kiln to various shades of yellow. (in common usage after the mid14th.C) This revolutionary development allowed craftsmen to use two colours within a single piece of glass.

3. By the application of transparent enamel colours (not in common usage until the 16th. C) This transparent colour developed as the availability of pot metal glass waned through a combination of war, pestilence and Fashion. It allowed virtuoso glass painting, particularly suited to heraldic devices. This material fires at a lower temperature than glass paint (typically 600 C) and can flake off leaving a distinctive disturbed surface. Blue enamel is particularly prone to this problem.

The Lead Came

Was cast into slender H-section moulds in the medieval period. Some survives in-situ, and should be noted and conserved. Latterly - since about 1500, lead has been milled through a wheeled machine to make various profiles. Characteristic mill-marks are left within the lead. It is very important that the characteristics of your glazing are noted and retained by the glazier. In particular the profile and depth of the H-section lead. There are two good reasons for this:

1) If a deeper heart lead than original is employed the weight of the panels, and the relationship to any support structure is set out of balance. Panels will buckle prematurely, and the necessary work of future glaziers in dismantling the panels will be far more traumatic for the glass.

2) It hardly needs saying that the profile of the lead is part of the original design. Any changes from this, especially allied to excess cement depth will fundamentally alter the texture and appearance of the glazing, and the façade of the building, especially externally.


Fixing methods and Metalwork

Completed panels of stained glass are normally set in to window openings into a groove in the stonework pointed both sides with mortar. The serious mistake of using cementitious mortar, often Portland cement has been made in the past. Only lime mortar should be employed as unlike cement based mortars it stays relatively soft and moves with the panels and surrounding stonework.

The panels sit one on top of the other at horizontal ‘divisions’, “saddled” by broad flanged leads.

At these panel divisions, and at other points, glazing bars set firmly into the stonework support the panels by the means of lead or copper ties soldered to the panels and twisted around the bars. There can be vertical bars or stanchions, set into lugs in the horizontal bars. These substantial iron support and security systems are often termed “ferramenta”.

Opening frames to allow ventilation are termed “casements.”

Environmental Protective Glazing

This is a system in which vulnerable stained glass is protected from damaging cycles of condensation, airborne pollutants and the ravages of weather by the introduction of an external glazing screen. The system has been in usage for at least 65 years in Europe; one of the first installations was at Berne Minster, Germany in about 1945.

Historically in terms of the aesthetic impact the results have been varied; some installations to major buildings have been without doubt disfiguring and unfortunate, whilst some have been a great success, subtly designed and functioning well.

There are a number of possible designs for such systems; for example the stained glass can be set inside the building, away from its original glazing groove, supported in a bronze framework. The new external glazing is set in the original position of the stained glass.

In alternative systems developed at the pre-eminent European stained glass conservation studio at Cologne cathedral, and in the UK by Holy Well Glass, Wells, the stained glass remains in its original position; the new glazing screen is in this case set on the exterior of the building.

In either case the outside layer is sealed, and the warmer air from the inside of the building is introduced into the gap- the inter space, between the two layers.

The aim is to provide airflow in the inter space and thermal buffering to encourage damaging cycles of condensation onto the new external glazing screen to minimise its occurrence on the historic glass. The stained glass is also isolated from the ravages of the weather.

There are pro and contra arguments for both systems, both technical and aesthetic which are complex and outside the scope of this brief explanation. What is certain is that there is no ‘one size fits all’ system; the protective glazing must be designed for, and be appropriate for each situation.


Perfectly tailored EPG frames at Exeter cathedral

The most appropriate method for this particular situation is the method detailed in the diagram below.

A new exterior glazing is installed in the original position of the stained glass, set into gauged lime mortar. (A) As these tracery panels are small, the exterior glazing is made in single pieces of hand -made cylinder glass, cut to size and fitted with a perimeter lead to allow expansion.

The interspace between the newly positioned stained glass and the new external glazing (B) would be 30mm.

The stained glass is cleaned and conserved and then reinstated inside the church, mounted on discreet bronze frames(C) which are laser scanned from templates and water jet cut from bronze to fir the stonework perfectly. The frames are held by clips fixed by non-ferrous fixings into nylon plugs (D).


Airflow is permitted around the stained glass by a lead perimeter skirt, which also prevents halation around the edge of the frame (E).

Such systems have been proven to work through environmental monitoring of installations and comparison with unprotected test areas. Environmental Protective Glazing is the only reliable method known to us at present to protect vulnerable works of Art in stained glass, it is at best an elegant conservation solution, functioning passively and adapting to differing environmental conditions.

Report Copyright Holy Well Glass.

Prepared by: Stephen Clare ACR. FMGP.

Reproduction or dissemination to third parties is prohibited

without the permission of the author.

E

condition report and conservation ... - newton abbot museum · st. leonard’s church, wolborough...

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