We have gathered a comprehensive amount of data on the pH dependence of both thermal stability and enzymatic activity of the triglyceride lipase cutinase from Fusarium solani pisi. Whereas the onset of activity is closely coupled with the deprotonation of the active site Histidine the loss of activity happens concurrently with the loss of structural stability. We have probed the dependence of thermal stability on the electrostatic composition of the protein surface, and whereas most mutants loose stability some displayed an increase in stability of several degrees. Consistently, all mutations either lost enzymatic activity or maintained an activity similar to the native enzyme. We also probed the effect of polyols on the thermal stability of cutinase at pH 8.5, and we are able to obtain more than 10 degree stabilization with sorbitol. We have investigated the thermal stability of cutinase using multiple modalities. In all cases we have scanning the thermal dimension with constant and reproducible scanning rates (10,20,30,40,60 and 90 degrees per hour). The technologies employed were Differential Scanning Calorimetry (DSC), Circular Dichroism (CD) and Fluorescence Spectroscopy (FS). Dynamic Light Scattering (DLS) was used to assess the approximate size of the protein entities. The DLS investigations showed that cutinase at temperatures below the unfolding transition at all concentrations used appeared as a monomer. The DSC data consistently reproted a lower unfolding temperature than did CD. Due to the relative insensitivity of the DSC method compared to the CD method, the cutinase concentration was 20-fold higher in the DSC experiments than in the CD experiments. Typically irreversible unfolding was observed with DSC, whereas the CD data indicated a more than 70% refolding under the conditions used. Temperature Scanning Fluorescence spectroscopy was used to investigate the concentration dependence of the unfolding reaction, and we are able to conclude that aggregation phenomena after the unfolding stabilizes the unfolded form, leading to a drop in thermal stability. In the case of cutinase we can document a more than 4 degree drop in thermal stability when increasing concentration 30-fold. This has serious implication for many protein engineering studies: all thermal stability measurements have to be performed under absolutely identical conditions, including protein concentration.