Introduction

The current text collects the most common damages that can be found in stained glasses. The objective is to spread this knowledge for the use of collections owners, heritage gestors and conservators-restorers that are not specialized in this field. The stained glass conservation is a less known specialty with materials and alteration mechanisms very away from other restauration fields.

Some specialties even being specialties share common points with other ones, but the analogies with the stained glasses are little useful in general. Stained glasses are movable property but the mayor part of them, unlike other goods, are exposed to weather and are building enclosures. In almost every case its conservation state must be judge in the long distance as unfortunately elevation means are not available for its diagnostic. In those cases restorer´s experience is an incalculable value factor.

The ignorance of this art often makes very easy for the owner or the responsible of the object to judge the conservation state of the stained glass and to stablish the minimum conservation strategy.

The stained glass is an object composed of very different materials, glass, lead, grisaille and enamel and the frames and/or mortars that hold the stained glass to the building.

MOST COMMON ALTERATIONS

1. Lead alterations

H-shape lead profile net is susceptible in a more or less complex of various impairments. The mayor part of acts use to be focused in its consolidation and in case of not being solved with the necessary readiness they finish causing irreversible damages and even the complete loss of part of the stained glasses.

  • Soffits curvatures: Is a very common deterioration and it uses to be easier to detect in the exterior side of the stained glass, watching it with reflected light. It can be due to a settlement of the structure although usually it is associated to other alterations, lead broken net in many points, bad dispositions of the reinforcements. In the case of being a touch solid structure could not require any intervention. It is an alarm sign and it must be consulted to a specialist.

 

  • Lead breakages:In function of many factors, such as the material composition and its fracture can appear breakages in the lead. They generally appear near the welds. It is a severe deterioration and in the case of being present in a generalized way around all the lead structure, could be the cause of the release of part of the ceiling. These structures are visible from the short distance in case of being located in difficult access places are undetectable.

 

  • Lead whitish aspect: This alteration is the metallic lead decomposition in lead carbonate. It is due to the unstable lead alloys, in general modern leads that are not alloy. It is an especially toxic material and the conservator must take cautions in its handling. This deterioration is accelerated with the presence of organic acids so often is linked to the use of acetic silicones in the stained glass installation or the protective glazing.

2. External waste and dirtiness

This is a complex paragraph and in some cases the cleaning of the stained glass is left to a professional without specific formation not only in stained glasses but in conservation-restoration. The main part and the most difficult one is detecting which parts are external wastes and which part are natural aging fruit of the materials.

The objective of the cleanings is removing external wastes that could affect the stained glass conservation rather recover translucency. Cleanings are irreversible processes that could be very dangerous for the integrity of the stained glass and they should be always left to special instructed technical.

Among the most common wastes that we found: dust accumulation, bird droppings, spider webs, remains of soot of candles, calcareous deposits, rust stains from frames and reinforcements, also stains waste like paints remains, varnishes organized from work carried out in the proximity of the stained glass. Cleaning with aqueous methods must be avoided if it is not made by a professional.

3. Glass

Glass is evidently a fragile material, but paradoxically is extremely durable if is conserved in favorable conditions. The major part of glass compositions are also very durable and unalterable.

Chemical glass damages

Chemical impairments in glass are due to unstable chemical compositions, like for example lower percentages to 60% of Si of lower presence of Ca. These are accelerated function to the aggressiveness of the environment they are exposed to. The stability in glasses function to its composition is a very complex topic. Microscopically the low stability of the glasses is displayed with very different phenomena, whitish scabs, surface bite, iridescence, micro fractures in all the material, opacity. Hostile conservation conditions would be the case of environments in which there were frequent condensations or very high relative humidity.

Fractures

Fractures can be caused by many reasons. They can be due to the poor realization of the pieces, bad executed stained glasses where the weight is not homogeneously distributed or can be due to external factors such as the impact of objects, birds, fortuitous impacts or vandalism. In the case of altered lead nets should cause the fracture of some pieces.

In the case of stained glasses exposed to dramatic temperature changes is frequent to find fractures caused by the thermal contrast.

Coloration changes

Some glass composition can change the coloration due to the oxidation change of the metallic oxides that gives color to the vitreous mass. It is frequent the transparent color change to pallid purple,

 

4. Paints alterations

La mayoría de vidrieras tienen vidrios pintados que se cuecen en hornos para fijarlas de forma casi permanente. Estas pinturas pueden ser dependiendo de su composición grisallas, esmaltes, amarillos de plata todos ellos con propiedades muy distintas. Sus mecanismos de degradación son muy complejos y pueden desarrollarse hasta la perdida casi completa de la pintura. En caso de detectarse coloración blanquecina, la pérdida de pintura en copos o la desaparición de partes de la pintura, llame a un especialista.

5. Frames and reinforcements

La estructura de plomo y vidrio va siempre sujeta por un marco perimetral tradicionalmente de hierro y dispone de refuerzos de pasamano o de varilla de sección circular que fijan los plafones en el marco. Estos elementos son más susceptibles a la corrosión que el plomo y su oxidación puede llegar a causar a causar daños en la vidriera. El más común es la mancha de óxido de la superficie cercana a estos. En casos extremos puede corroerse completamente y dejar de ejercer su función. Hay que estar atentos a las filtraciones que puedan acelerar este fenómeno.

Stone and mortars

En el caso de la instalación más tradicional, en iglesias, las vidrieras se instalan en tracerías y maineles más o menos complejos. Estas estructuras no son completamente rígidas y sus leves movimientos pueden causar fracturas en los vidrios y curvar los plafones.

En algunos casos los morteros se agrietan y desprenden dejando de ejercer su función de sujeción.

6. What to do in case of accident

En caso de accidente fortuito será de gran ayuda una actuación diligente tras este. Asegurar el espacio en el que pueden desprenderse partes del vidrio. Una vez hecho esto recoger los fragmentos desprendidos por muy insignificantes que puedan parecer. En caso de que sea imposible que lo realice el conservador debe realizarlo el mismo responsable de la conservación del objeto. Estos fragmentos pueden ayudar en gran medida a la restauración del objeto. Fotografiar la vidriera lo antes posible para dejar constancia del accidente, estas fotografías serán útiles al seguro que pueda cubrir los gastos generados en el accidente.  Llamar lo antes posible a un profesional capaz de confeccionar un presupuesto, asegurar la vidriera para evitar que los daños proliferen, y empezar una intervención de conservación restauración. Un análisis del accidente puede enseñar cuales han sido las causas y minimizar los riesgos con medidas sencillas.

7. What points do we have to observe in the revision of a stained glass conservation 

Una inspección rutinaria y programada periódicamente debería hacer un seguimiento de todos los elementos que puedan dar información sobre el estado de conservación de la vidriera. Como a menudo se realiza a distancia no solo hay que observar el objeto si no también su entorno más próximo. Debería observarse.

  • No hay curvaturas en los plafones.
  • No hay filtraciones de agua.
  • No hay pérdidas de pintura en las partes pintadas.
  • No hay fracturas en los vidrios.
  • Los morteros o masillas están en su lugar sin grietas ni desprendimientos.
  • El plomo no tiene coloración blanca ni fracturas.

 

Para cualquier duda o información nos puede contactar en info@vitrallsbonet.com

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