Agar gel loaded with micro-emulsion could be used to extract lipophilic materials from porous surfaces. The physical properties of the gels are good enough for a conservation work. They allow the micro-emulsion to flow on the porous surface and to wet it but maintain the micro-emulsion in its structure and prevent the formation of rings. https://www.countryscenesaddleryandpetsuppliers.shop/product-category/work-and-harness-leather-headstalls/