Final answer:
The white film on cutlery after dishwasher use is likely due to hard water residues that react with detergent and precipitate onto the steel surfaces. Glassware might not show the residue because of its smoother surface and the action of specific components in the dishwasher detergent designed to prevent spotting.
Step-by-step explanation:
The white film left behind on steel cutlery but not on glassware after using a commercial dishwasher can be attributed to the reaction of hard water with the washing detergents. High salt content in local tap water often means the presence of calcium and magnesium ions, which react with phosphates in the detergent to form insoluble compounds that can precipitate onto surfaces as a white film. This is more prevalent in items with larger surface areas and crevices such as cutlery.
The reason glassware might not show this residue could be due to the surface properties of glass. Glasses have a smooth surface that allows water and detergent mixtures to flow off easily, especially with the help of rinse aids typically present in commercial dishwashing processes. Moreover, some dishwashing detergents contain compounds like non-ionic surfactants and anti-corrosion agents that prevent spotting and corrosion, which may contribute to a clear finish on glassware.
On the other hand, cutlery often has edges and textured areas where water and detergents can accumulate and leave residue as they dry. Also, stainless steel can react differently with various minerals in hard water compared to glass, making it more likely to show signs of residue.