What type of stains is least likely to be removed by water-based solutions?

Ink stains are least likely to be removed by water-based solutions because they often contain dye pigments and solvents that do not dissolve in water. Ink is typically formulated with oil-based components or other strong bonding agents that adhere to the fabric fibers, making it difficult for water to penetrate and lift the stain effectively.

On the other hand, food spills, watercolor marks, and tea stains generally consist of substances that are more water-soluble. These types of stains can often be addressed with water-based cleaning solutions, as they do not have the same level of adhesion or stubbornness that ink possesses. Water-based solutions are more effective on organic compounds and soluble materials, allowing them to break down and lift stains that can dissolve in water.