Trisodium phosphate has cleaned grease off kitchen walls, mildew off siding, and chalking off old paint since the 1940s. A properly mixed tsp cleaning solution dissolves nicotine film, oily fingerprints, and oxidized paint better than nearly any consumer spray on the shelf, which is why painters still keep a box of Savogran or Klean-Strip TSP in the truck. The catch: it is strongly alkaline, banned or restricted in several states, and demands real personal protective equipment to use safely.
What TSP Actually Does Chemically
TSP raises the pH of your wash water to roughly 12, which saponifies oils and lifts them into solution. It also etches glossy surfaces just enough for primer to bite, eliminating the need to sand entire walls before repainting. At a 1/2 cup per gallon dilution, it cuts through 20 years of kitchen grease in one pass. No rinse-and-go cleaner matches that performance.
Standard Mixing Ratios
- Light cleaning of painted walls: 1 tablespoon per gallon of warm water (around 100 degrees F).
- Heavy degreasing or pre-paint prep: 1/2 cup per gallon.
- Exterior siding, decks, and mildew removal: 1 cup per gallon, often combined with 1 quart of household bleach.
- Concrete and masonry stripping: 1.5 cups per gallon applied with a stiff nylon brush.
Always add TSP to the water, never the reverse, and stir with a wooden paint stick until dissolved. Use a 5-gallon bucket so the splash zone stays contained.
Where TSP Earns Its Keep
Pre-paint prep on kitchen cabinets is the classic use. Wipe every door and box with a TSP-soaked sponge, let it dwell 60 seconds, then rinse with clean water and a microfiber. Skip this step and your Benjamin Moore Advance topcoat will fisheye over invisible cooking oil within a week. The same logic applies to bathroom walls before repainting, garage walls before epoxy floor coating, and any exterior surface before a fresh coat of Sherwin Williams Duration.
For decks, a 1 cup per gallon mix plus a quart of bleach kills mildew and lifts gray UV-damaged wood fibers. Apply with a pump sprayer, agitate with a deck brush on a pole, dwell five minutes, and rinse with a garden hose at city pressure. Skip the pressure washer at full blast or you will fuzz the boards.
Safety Gear That Is Not Optional
TSP at painting strength burns skin within a few minutes of contact and will permanently scar the cornea if it splashes into the eye. Wear:
- Long chemical-resistant gloves (nitrile, not latex), 18-inch gauntlet length.
- Sealed safety goggles, not just glasses.
- Long sleeves, long pants, and closed-toe shoes you do not mind ruining.
- A respirator with P100 cartridges if mixing the dry powder in an enclosed space.
Ventilate the room, open a window, and keep kids and pets out for the duration. Never combine TSP with ammonia-based cleaners. Bleach is okay; ammonia is not.
State Restrictions and Phosphate-Free Alternatives
Sixteen states regulate phosphate content in household cleaners due to algae blooms in lakes and rivers. Stores in those regions sell TSP-PF, a phosphate-free substitute using sodium metasilicate and sodium carbonate. It cleans nearly as well at the same dilution but rinses cleaner and is far easier on septic systems. For most residential pre-paint prep, TSP-PF from Savogran ($8 for a 1-pound box) is the smart default.
Rinse Step Most DIYers Skip
Even diluted TSP leaves an alkaline film. If you paint over it, the film interferes with adhesion and can chemically attack the binder in latex paint. After washing, go over every surface twice with clean water and a fresh sponge, changing the water when it looks cloudy. Let the surface dry overnight before priming. A handheld moisture meter like the General MMD4E reads below 12 percent on drywall when it is truly ready to paint.
When to Skip TSP Entirely
Do not use TSP on unpainted aluminum, glass with mineral deposits, or polished marble. The high pH etches all three. Quartz countertops tolerate it briefly, but rinse within a minute. Wood floors finished with polyurethane handle a 1 tablespoon per gallon mix for cleaning, but never use the painter’s prep strength on hardwood, it will dull the finish in seconds.
Buying and Storage
A 4.5-pound box of Savogran TSP runs $9 to $13 at any Home Depot or Lowe’s. One box mixes roughly 14 gallons at heavy strength, enough for an average exterior house wash. Store the dry powder in a sealed plastic bin away from humidity. Once mixed, use the solution within 24 hours and dispose of leftovers through household drain only if local code permits.
A TSP cleaning solution is not glamorous, but for any painter who wants a topcoat to last 10 years instead of three, it remains the single most valuable item in the prep arsenal. Mix it carefully, rinse thoroughly, and respect the chemistry.
Common DIY Mistakes
The most expensive mistake is skipping the rinse and going straight to paint. The alkaline film prevents primer from bonding, and within six months you see paint peeling in sheets, especially in steamy bathrooms. Another common error is using TSP at full painting strength to clean light dust off walls; the strong solution etches the existing paint and creates a chalky surface that needs primer to recover. Match the dilution to the job, always.
Mixing TSP in a metal bucket also causes corrosion that contaminates your wash water with rust streaks. Stick to plastic buckets and plastic stir sticks. Never use the same sponge for TSP and clean rinsing; the residue undoes everything. Keep two separate buckets and two separate sponges, and label them with painter’s tape so nobody mixes them up mid-project. The discipline pays off in finish quality on every paint job you tackle.
