A "last resort" cleaner for stone and grout is classified as a __________ cleaner.

A "last resort" cleaner for stone and grout is classified as an acid cleaner because acid cleaners are specifically formulated to address tough stains and restore the surface of stone and grout that may have been damaged by lingering deposits, mineral buildups, or soap scum. These cleaners work by breaking down the chemical bonds of these stubborn substances, making it easier to remove them without excessive scrubbing.

Using an acid cleaner is generally reserved for situations where traditional cleaning methods have failed, as they can be harsh on certain surfaces. While they can effectively clean, they may also risk etching or damaging sensitive types of stone, which is why their use is recommended as a last resort. Proper dilution and application techniques must be followed to minimize potential damage while achieving desired cleaning results.

In contrast, neutral, detergent, and alkaline cleaners are typically safer options used for regular cleaning. Neutral cleaners are pH-balanced and gentle on surfaces, making them suitable for routine maintenance. Detergents usually contain surfactants that help lift dirt and stains, while alkaline cleaners work well on organic soils but may not be effective against mineral-based deposits. Therefore, acid cleaners serve a very specific role in cleaning applications, highlighting their classification as a last-resort option.