Acrylic can lose gloss or reproduce weak detail when the sheet surface is not in the right condition at tool contact. Underheated material may resist fine geometry, while excessive heat can create surface instability, marking, or unwanted tool transfer.
Cast and extruded acrylic do not use one interchangeable recipe. Thickness tolerance, molecular structure, forming range, and response to stretching differ by product. Tool finish and air evacuation strongly affect the final optical surface.
Diagnosis
The dull region should be compared with vent locations, tool texture, and sheet temperature. A local patch often indicates trapped air or incomplete contact. Uniform loss of gloss suggests sheet condition, forming temperature, or the selected acrylic product.
The tool must have the finish required on the part, and the sheet must contact it without sealed air pockets. Heating changes should be based on measured sheet behavior and supplier guidance, not a universal acrylic temperature.