Revealing the face of the past: a systematic review on the use of eco-friendly hydrogels for cleaning of heritage painted surfaces

Purpose This review aims to present a comprehensive review on the use of hydrogels, and specifically eco-friendly formulas, for cleaning heritage painted surfaces, including their classification, characteristics and applications. Design/methodology/approach This review illustrates several types of hydrogels, physical or chemical and their classification based on source, composition/the polymer structure and the electric charge. The swelling characteristics, mechanical-biocompatible properties, the advantages and disadvantages of gel application in the field of cultural heritage conservation are also discussed. The review presents examples of physical and chemical hydrogels and their preparation methods. Findings The review highlighted the characteristics of different eco-friendly hydrogels and showed that the mechanical properties of gels can be modified by changing their composition; this feature allows them to be successfully applied for cleaning of cultural heritage objects. Originality/value This review highlights the major features of eco-friendly hydrogels, and it draws an attention to their efficiency for cleaning purposes.