Investigating Accepted and Innovative
Materials for Glass Fills
There are a limited number of material choices a conservator has when filling losses in glass, and those typically used each have their own benefits and limitations. While conservators typically turn to epoxies, polyester resins, or Paraloid B-72, there is interest in finding alternative materials with better working properties, chemical stability, and reversibility. The aim of this independent study was to gather information about both well-established and new or unique materials used to create fills for glass by engaging with published sources and colleagues from various institutions and conservation programs across the globe.
The objectives of this study were to: (1) produce an annotated bibliography of published sources discussing current methods/materials used for glass fills in conservation; (2) gather anecdotal evidence from conservation colleagues regarding preferred and alternative methods/materials used for glass fills; (3) compare and contrast commonly used and innovative materials for creation of glass fills through hands-on experimentation on non-collection objects; and (4) produce a report summarizing techniques currently in use in the field and findings of exploration with new materials.
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A survey was widely distributed across the United States and abroad, and participants were asked about preferred and alternative methods and materials for glass fills in their work. As expected, epoxy and Paraloid B-72 are favored fill materials for glass. Mulberry paper is gaining more traction; however, it is typically only used on archaeological glass, not decorative glass where desired clarity is an issue. Interestingly, 13% of respondents shared that they have or are currently experimenting with innovative fill materials or have a desire for further research into them. Respondents expressed that they wanted materials with better working properties (no bubbles like B-72 or epoxy), less toxicity (better for health and safety) and better sustainability (biological vs petroleum derived materials). While many are interested in finding new materials for fills, very few have researched or tested these materials, and none have published their results, yet.
Glass fill materials currently in use by conservators
Based on information gathered from published sources, as well as anecdotal evidence from working conservators, the following fill materials and techniques (Paraloid B-72, Hxtal epoxy resin, mulberry paper, agar bioplastic, and nanocellulose film) were tested on study collection glass objects varying in color, thickness, and clarity. Through hands-on experimentation, the working properties and aesthetic viability of new and innovative materials were compared to traditional material options for glass fills. Each fill material was tested on clear and colored glass objects for the purposes of comparison.
Experimenting with casting epoxy fills in situ: (1 & 2) Adhering mold in place with new silicone over area of loss, (3) Silicone mold adhered in place and ready for epoxy to be poured, (4) Injecting epoxy into mold.
Experimenting with Paraloid B-72 fills: (1) Color matching with Orasol dyes in ethanol, (2) Casting tinted B-72 into silicone molds placed in polyethylene bags to slow solvent evaporation, (3) Creating a Mylar stencil of the loss and cutting the shape out of the cast B-72.
Experimenting with mulberry paper fills: (1) Color matching with Golden Fluid Acrylics, (2) Coating toned and cut paper fill with 30% Paraloid B-72, (3) Placing fill onto glass object.
Experimenting with nanocellulose fills: (1) Nanocellulose (CNC and CNF) poured into petri dishes lined with silicone-release Mylar, (2) Cutting nanocellulose film, tinted with acrylic paints, to shape of fills.
Experimenting with agar fills: (1) Materials for making agarose hydrogel, (2) Adding color matched orasol dye mixture to heated agarose before it sets, (3) Tinted agarose cast into plasticine molds on a glass sheet before being cut to shape.
After testing a variety of traditional and innovative materials for glass fills, I have a much better working knowledge of these materials and appreciation for the skill it takes to create good glass fill. While epoxies and B-72 have obvious practical benefits, their respective drawbacks necessitate research into alternative materials. Despite its challenges, agarose stands out as a potentially viable option and deserves further research and experimentation. I hope this project serves as a helpful summary of the current state of conservation fills for glass and as a jumping-off point for those seeking alternative materials with potentially better working properties.
