Describes the design and construction of a microclimate box containing silica gel, prepared to be fitted inside the gilt frame of a panel painting. Gives a description of the atmospheric conditions of its London housing place, involving high humidity and temperature variations as well as pollution. Presents the problems of the painting, <i>A musical party</i> by Duyster, and gives reasons for the choice of a local microclimate. The construction, materials, and fittings of the Perspex box, including adhesives used for construction and sealing, are detailed next. The box was monitored in the studio for some months prior to its reinstallation in its former location, within a deeper gilt frame. An auxiliary control experiment is reported, accompanied by summarized statements on the results, a list of possible improvements, and a list of materials and suppliers. -- SCMRE