Several factors can influence the effectiveness of fixation:
pH: Most fixatives work best at a neutral pH (around 7.0). Temperature: Fixation is generally performed at room temperature, although some rapid fixations are done at lower temperatures to slow down enzymatic activity. Concentration: The concentration of the fixative affects the rate and extent of fixation. Higher concentrations may fix tissues faster but can also lead to over-fixation and tissue hardening. Time: The duration of fixation must be optimized; prolonged fixation can lead to excessive hardening and shrinkage, while insufficient fixation can result in poor preservation. Penetration: Fixatives must penetrate tissues adequately. Larger tissues may require slicing to ensure proper fixation throughout the sample.
