Aqueous gel cleaning systems were introduced in the 1980s. Subsequent research has addressed some concerns regarding their use, particularly the potential of any gel or its components to be detrimental to the treated surface. One aspect of a collaborative project involving the Getty Conservation Institute included quantitative measurement of gel residue on samples of an aged test painting using radioactively labeled components of the gel. This paper presents results of a follow-up study that targeted problems of gel cleaning of three-dimensional objects with complex surface topography and higher porosity. Quantitative measurement conducted on gilded wood, plaster, unglazed terracotta and marble showed, as expected, that porous surfaces are far more prone to gel retention than low-porosity materials. The study also showed that gel procedures developed for non-porous surfaces lack the efficiency necessary to clear porous surfaces, and that highly porous surfaces can retain up to 10 times more gel than those with low porosity. -- SCMRE