It will probably not come as any surprise to hear that painting conservators are frequently preoccupied by glue. What may be less obvious to a client is the science and art of a glue’s nature that preoccupies their painting conservator. The use of glue in the treatment of any damage is an art in itself, with each type of adhesive serving a unique purpose in preserving the integrity of the artwork.
From consolidating fugitive paint to applying patches to strip-lining and full re-lining, the choice of glue is a critical part of the process. In many cases I will make my own glue, adjusting the ingredients and blend to match the specific requirements of each individual piece.
Types of Glues Used in Painting Conservation
Choices have increased over the centuries. In the beginning the conservator was restricted to the same range of glues that the original artist accessed. These were organic, such as animal glues derived from collagen, to bond the canvas to its support. Their vulnerability to fluctuations in humidity and temperature made them less than ideal for ensuring the long-term stability of the artwork, and this motivated conservators to experiment with synthetic alternatives.
In the 20th century, the advent of synthetic adhesives marked a significant shift in the field of painting conservation. Polyvinyl acetate (PVA) emerged as a popular choice due to its stability and reversible nature, allowing conservators to adapt their methods to changing conservation philosophies. However, even within the realm of synthetic glues, conservators continued to experiment and refine their techniques to achieve the best possible results.
Animal Glues
- Derived from collagen, typically sourced from hides and bones of animals.
- Traditionally used in the past but their susceptibility to environmental conditions makes them problematic for sustaining a painting’s longevity..
- I find, however, that there are occasions when the natural and reversible properties of animal glues make them the best option for the painting conservator.
Polyvinyl Acetate (PVA)
- A synthetic adhesive that gained popularity in the mid-20th century.
- Known for its stability and versatility, PVA provides a strong bond. The strength of the bond can make it hard to reverse so adding it to a wheat starch paste.
- Widely used in the conservation of paintings, especially for its compatibility with canvas.
Beva® (Beva 371 and Beva 371b)
- A proprietary adhesive consisting of a mixture of ethylene vinyl acetate copolymer and beeswax.
- Beva® offers a stable bond, making it a favoured choice for many painting conservators. However it is difficult to reverse and the high temperature that is required to activate its adhesive properties can be damaging to the artwork.
- Particularly effective in consolidating fragile paint layers.
Acrylic Dispersion Adhesives
- Acrylic-based glues, such as Lascaux 360 HV, are gaining popularity for their stability and ease of use. Again, acrylics can be tricky to remove and the long term impact of these newer chemicals on paintings has yet to be seen.
- Known for their transparency and compatibility with a wide range of materials.
Choosing the Right Glue: A Discussion with a Client
When it comes to selecting the appropriate glue for relining a painting, a crucial aspect of my job as a painting conservator is to communicate effectively with the client. Understanding the specific needs of the artwork, its historical context, and the client’s preferences are all key factors in making an informed decision.
Historical Context
I will always consider the era of the painting and the materials commonly used during that time. Choosing an adhesive that aligns with the historical practice at the time when the original was made not only preserves its authenticity, but also often minimises the impact on the painting’s integrity.
Condition of the Artwork
Naturally, the only reason a glue would be required would be if the painting has certain types of damage. My choice of glue will primarily be dictated by the specific conservation needs of the artwork.
Long-Term Stability
When a client comes to me I will ask where the painting has been stored and where it will be stored after the work has been completed. Often environmental conditions have been the cause of the damage that I am being asked to repair. If it is determined that the environment will continue to put strain on the painting then I would opt for a glue that offers stability and longevity, ensuring the preservation of the piece for future generations.
Reversibility
Painting conservators should never intervene in a way that is not reversible. Practice and ethics evolve over time so any decision that I make today has to be something that can be undone in the event that best practice changes. Many paintings have been destroyed by over-enthusiastic conservators who took action that further eroded the integrity of the original and cannot be reversed. It is likely that whatever repair needs to be made a glue will be required, and that adhesive has to be removable in the future if required. An adhesive’s degree of reversibility should be critical to the painting conservator.
In Conclusion
The world of painting conservation is a delicate dance between tradition and innovation, and the choice of glue in the relining process plays a pivotal role. From animal glues of the past to modern synthetic adhesives, each has its merits and considerations. By understanding the historical trends and engaging in open communication with clients, I will always endeavour to ensure the preservation of our cultural heritage while embracing the advancements of the present.