The intensity of light reflected by lubricating grease- its sheen or brilliance.Â Luster should be described as follows:
- Â Bright â€“ Reflects light with a relatively strong intensity.
- Â Dull â€“ Reflects light with a relatively weak intensity. Some greases with a high water content may have a dull luster. Certain thickeners and fillers give a grease a characteristic dull luster.