Vomit mixes bile from the digestive process with the foodstuffs themselves. Cat urine is not comparable to human urea, as it contains a sulfur molecule. Each is broken down and removed by enzymatic actions specific to the molecular structures. Polyester or acrylic, in contrast, will repel water-based stains but adsorb oily ones unless a special finish has been fixed on those fibers. Consequently, the success of a stain removal method depends upon the fiber type and finish.
Older fabrics loose their resistance to tearing, to stretching, and to rubbing.
Removing a fresh stain from an old textile may require too much stress on the fabric and leave a rip where there was only discoloration before. Thus, many drycleaners and conservators are reluctant to risk this additional damage to an old textile. Stain removal requires an appropriate work area and appropriate supplies. The stain should never be rubbed because this can abrade or rip the fabric. Stain removal is sequential and repetitive, because removal involves taking off a percentage of a stain with each application.