Cleaning Chemistry and Methods
Cleaning chemistry and methods is where the exam tests pH, surfactant function, dilution, dwell time, and matching a method to fiber and soil. You need to know why an alkaline pre-spray helps oily soil and why rinsing matters as much as cleaning.
Chemistry essentials
- pH: alkaline solutions above 7 saponify oils and lift particulate; acidic solutions below 7 neutralize, aid rinsing, and help with urine or rust. Wool and stain-resistant nylon have upper pH limits; strong alkali can strip stain resist or damage wool.
- Surfactants: anionic surfactants work well on particulate and oily soil; nonionic surfactants are low-foam and general-purpose; cationic surfactants offer antimicrobial or static benefits. Builders soften water, solvents cut grease, enzymes digest protein, and oxidizers or reducers treat dye stains.
- Dilution and dwell: follow the label ratio exactly; more chemical is not better. Allow 5–10 minutes of dwell, keep the pre-spray wet, then rinse or extract.
Method selection
Use hot-water extraction for restorative deep cleaning; encapsulation and bonnets for interim work; dry compound where moisture is restricted; absorbent pads for spotting. The sequence is vacuum, pre-spray, agitate, dwell, rinse or extract, then dry.
Worked example
A 32 oz sprayer needs 1:64 dilution. 32 ÷ 64 = 0.5 oz concentrate, so add 0.5 oz chemical to 31.5 oz water. For a 5-gallon batch, 640 ÷ 64 = 10 oz concentrate plus 630 oz water. The reasoning: dilution ratios are chemical-to-water by volume, and mixing 1 part into 64 parts total is a common error.
Traps
Mixing bleach and ammonia; using high pH on wool; over-wetting and leaving residue that attracts soil; skipping the rinse; insufficient dwell time; and treating coffee or urine with the wrong chemistry without testing in an inconspicuous area.