What should always be tested before using a stain remover on upholstery?

Testing a stain remover's compatibility with the fabric and its colorfastness is essential because different fabrics can react differently to cleaning agents. Using a stain remover without testing can lead to irreversible damage, such as discoloration or deterioration of the fabric. Colorfastness tests help ensure that the upholstery will not bleed or fade when the cleaner is applied.

This precaution is crucial in upholstery care, as fabrics can vary greatly in terms of construction and materials, making them more susceptible to certain chemicals. By conducting a test in an inconspicuous area, you can confidently determine the effectiveness and safety of the stain remover before applying it to a visible spot. Thus, testing for compatibility and colorfastness is a fundamental practice in maintaining the integrity and appearance of upholstery.