Soiling conditions
Soiling conditions
This domain tests whether you can classify soil before choosing chemistry. Soil is rarely one substance: particulate, oily, protein, water-soluble, and bonded soils often coexist. The exam expects a soil diagnosis, not a generic 'shampoo.'
Core rules
- Separate loose particulate from bonded soil. Dry soil removal with a quality vacuum is the first cleaning step and reduces mud-making.
- Classify by chemistry: particulate/clay/carbon; oily/greasy (kitchen, parking lot, cosmetics); protein (blood, milk, vomit); tannin (coffee, tea, wine); dye/ink; rust; and filtration soil.
- Note location and depth: entry soil, traffic-lane soil, spot/stain, filtration lines along walls, pet contamination in backing, and wicking from backing.
- Consider fiber and finish: soil-hiding colors, stain resist, fluorochemical protectant, and wear can make soil look lighter or darker.
- Soil load and pH affect prespray choice, dwell, agitation, and rinse. Urine requires saturation/extraction and subfloor checks, not just surface spotting.
Worked example
A light gray polyester living room has black wavy lines at the baseboard and sticky dark traffic lanes near a kitchen. The tech identifies filtration soil (fine carbon/particulate driven by air pressure) and grease tracking. He dry-vacuums, uses a strong alkaline pre-spray on the grease with dwell, agitates, extracts, then treats filtration lines with a specialized particulate/alkaline method and controlled moisture. He warns that filtration lines may not clear completely because soil has penetrated the backing. Reasoning: the two soils need different chemistry, and over-wetting risks wicking.
Traps
Calling every dark mark 'pet urine'; using protein spotter on tannin stains; over-wetting filtration soil and driving it deeper; and promising removal of dye or corrosion stains. Always pre-test and explain that stain 'removal' can mean improvement, not invisibility.