Primers marketed as “acid-free” in the context of cosmetics or art supplies typically indicate a formulation that does not contain acids like phosphoric acid or citric acid as primary active ingredients. However, all aqueous solutions, including these primers, possess a pH value. This value represents the measurement of hydrogen ion concentration and determines whether a substance is acidic, neutral, or alkaline. A pH of 7 is considered neutral; values below 7 indicate acidity, and values above 7 indicate alkalinity. For example, while an “acid-free” primer will not contain intentionally added strong acids, it will still register a measurable pH.
The emphasis on “acid-free” formulations stems from concerns regarding potential skin irritation or damage to delicate surfaces, particularly in art conservation. Strongly acidic primers can be corrosive or cause sensitivity reactions. The benefit of using primers without these added acids lies in their generally milder nature, making them suitable for individuals with sensitive skin or for applications where minimizing the risk of material degradation is paramount. Historically, the introduction of acid-free options reflects a shift towards safer and more preservation-conscious practices within both the cosmetic and artistic fields.
