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Solubility and polarity

Like dissolves like. Three words that predict which branch a stain belongs to before anything has been tried.

In detail

Whether a substance dissolves in a liquid depends mostly on whether the two are alike in polarity. Water is strongly polar, so it dissolves salts, sugars, many dyes and most of what a body produces. Oils, waxes, resins and greases are non-polar, so they dissolve in non-polar solvents such as white spirit and, more aggressively, acetone. That is the whole of 'like dissolves like', and it is the most useful predictive rule an ordinary person can carry into a cleaning problem, because it sorts a stain into a branch before any product has been chosen. The carpet institute's database is that rule made into a procedure: coffee, wine, juice and food colouring go to the aqueous branch; butter, gravy, cooking oil, wax, nail varnish, oil paint and felt-tip marker go to the solvent branch, before any water. Detergent is the third case, and it exists precisely because most real soil is a mixture: a surfactant does not dissolve oil, it makes oil travel in water, which is how one product covers both branches at once. The rule also predicts damage — a solvent that dissolves a stain will dissolve any finish made of similar material.

Why

Sources for this page

Sources

  1. Spot Solver: spot and spill removal procedures

    The Carpet and Rug Institute (CRI) · Trade or professional body

    Relied on for: That the database routes greasy and resinous deposits to a dry-cleaning type solvent before any water, and water-soluble deposits to a detergent solution first. (states this directly)

  2. Right to Know Hazardous Substance Fact Sheet: Acetone (RTK 0006)

    New Jersey Department of Health, 2015 · Government or regulator

    Relied on for: That acetone is a solvent for fats, oils, waxes, resins, plastics and varnishes. (states this directly)

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