Art restoration is the process through which we rejuvenate works of art that have succumbed to the ravages of time, sustaining damage due to environmental conditions, neglect, or even well-intentioned but misguided earlier restoration attempts. It's a delicate field, one that straddles the boundaries of art, science, history, and ethics. While employing advanced technology and cutting-edge techniques, art restorers must also possess a deep understanding of the original materials used by the artist, the artist’s intent, and the socio-cultural context in which the work was created. In order to select the right art restoration specialist for your masterpiece, it's crucial to ask the right questions, to evaluate their proficiency, experience, and ethical grounding.

One of the integral attributes of a competent art restorer is an extensive knowledge of art history. This is not a mere appreciation of the aesthetic aspects, but rather the ability to see the artwork in the context of its era, understanding the socio-cultural influences that shaped its creation. An art restorer must be well-versed in the materials and techniques used by artists at different periods of time. For instance, the type of pigments used in the Renaissance period differed significantly from those used during the Impressionist era. Hence, you may ask your potential restorer, "Can you describe the materials and techniques that were used during the time my artwork was created, and how that impacts the restoration process?"

The methodologies and technologies applied in the restoration process are another critical area to probe. The relatively recent advent of infrared reflectography, for example, has been revolutionary in the field of art restoration, allowing restorers to look through layers of paint to see the artist's initial sketches or changes made during the painting process. Similarly, X-ray fluorescence spectroscopy can help restorers detect the elemental composition of pigments without damaging the painting. However, each of these technologies has its pros and cons. Infrared reflectography, for instance, may not detect certain pigments, while X-ray fluorescence spectroscopy may not be effective for pigments that do not contain metal. Thus, it would be prudent to ask, "What technologies would you use for the restoration of my artwork, and why do you believe they are the best choice?"

Considering the inherent uncertainties and risks involved in restoring any work of art, it is essential that the conservator has comprehensive insurance coverage. Here, professional indemnity insurance becomes a key factor. This provides protection for the restorer against claims for negligence or malpractice. Therefore, you must ask, "Do you have professional indemnity insurance, and to what extent does it cover potential damages to my artwork?"

Furthermore, it’s important to question the ethical principles that guide the restorer's practice. The American Institute for Conservation (AIC) Code of Ethics stipulates, among other things, that any treatment must strive “to respect the integrity of the cultural property,” and that all actions must be “fully documented and reversible.” You should ask your potential restorer, "What are your guiding ethical principles in the restoration process, and how do you ensure that your actions are in line with these principles?"

As a final consideration, consider asking for references or viewing past restoration projects. Observing the restorer's previous work, especially if it involved similar types of artwork, will help you gauge their proficiency and reliability. Ask them, "Can you provide references or examples of similar projects you’ve worked on?"

Art restoration is not merely a task, it's a responsibility. It's about giving a second life to a work of art, ensuring that it continues to inspire, educate and enthrall future generations. Therefore, selecting the right restorer for your masterpiece is a decision that requires careful deliberation and informed judgment. By asking the right questions, you can ensure that your chosen expert possesses not just the technical expertise, but also the ethical grounding and historical understanding that this delicate task requires.