TSP (Trisodium Phosphate)
Dilution Calculator
TSP is the high-alkalinity pre-paint cleaner that removes grease, soot, and glossy-surface residue before repainting. This page launches the main Alliance Chemical calculator preloaded with TSP stock and explains the typical cup-per-gallon recipes behind the math.
Start With The Common TSP Jobs
TSP dilution intent clusters around three jobs: pre-paint wall prep (the most common), heavy-duty degreasing before refinishing, and exterior siding wash. These launchers match those directly.
10% → 2.5%
Preload a 1-gallon 2.5% solution — roughly the "½ cup per gallon" paint-prep recipe printed on many TSP boxes.
Open Preloaded Calculator Heavy Cleaning10% → 5%
Launch a 1-gallon 5% solution for greasy kitchen walls, range hoods, and workshop surfaces before refinishing.
Open Preloaded Calculator Siding Wash10% → 1%
Milder 5-gallon 1% solution for exterior siding, deck cleaning, and applications where 2.5% would strip finish.
Open Preloaded Calculator Ratio Mode1 : 4 Water
1:4 dilution of 10% stock for a 2% working solution when SOPs are written in parts rather than final percent.
Open Preloaded CalculatorUnderstand The TSP Recipe Pattern
TSP ships as crystalline dodecahydrate powder. Boxed consumer TSP uses "cups per gallon" recipes that don't scale cleanly; the dilution calculator converts any target percentage back to clean gram and volume math.
Two ways to mix TSP. Option A: dissolve the target grams of powder into your final water volume — simplest when you know the target percentage. Option B: make a 10% w/v stock in a dedicated container and dilute from it — useful when you batch regularly and want consistent math.
Typical recipes. The classic "½ cup TSP per gallon water" works out to roughly 2.5% w/v — standard pre-paint prep for greasy or glossy surfaces. A heavier 1 cup per gallon hits ~5%. Lighter siding-wash recipes run around 1% (roughly 2 tablespoons per gallon). The calculator above returns exact gram amounts.
Which product. Alliance Chemical sells Trisodium Phosphate Dodecahydrate in ACS Reagent Grade — higher purity than most hardware-aisle boxed TSP, with predictable dissolution and no added fillers that leave residue.
Mind the "phosphate-free" alternatives. Boxed "TSP substitute" products replace phosphate with sodium carbonate or similar. They clean, but not as aggressively as real TSP. When a paint manufacturer spec calls for TSP, the substitute may not meet prep requirements.
Common TSP Dilution Targets
TSP working strength depends on surface, soil load, and whether paint or finish is going on top. Pre-paint prep is the most common; lighter solutions work for exterior wash; heavier for degreasing.
| Starting Stock | Target | Typical Use | Notes | Launch |
|---|---|---|---|---|
| 10% w/v stock | 2.5% | Pre-paint wall prep | The ½-cup-per-gallon standard. Dulls glossy finishes, removes grease and soot, allows primer to bond. Rinse thoroughly before painting. | Open |
| 10% w/v stock | 5% | Heavy degreasing | For range hoods, kitchen walls, workshop floors before refinishing. Scrub with abrasive pad for embedded soil. | Open |
| 10% w/v stock | 1% | Exterior siding and deck wash | Mild enough for siding, trim, and deck boards without stripping stain. Pair with soft-bristle brush; rinse thoroughly. | Open |
| 10% w/v stock | 1:4 water | Ratio-mode SOP | One part stock to four parts water lands at roughly 2% — adjacent to the standard 2.5% prep target when SOPs are written as parts. | Open |
TSP Handling Reality Check
TSP is a strong alkali — pH around 12 in solution. That is what makes it effective at cutting grease and etching gloss, but also what makes it aggressive on skin, eyes, and sensitive substrates.
Alkali burns, not acid burns. TSP is basic, not acidic. The burn pattern is slower and deeper than acid burns — you may not feel it for minutes, and damage continues until the solution is rinsed off. Gloves and eye protection are non-negotiable.
Etches gloss, dulls paint. That is a feature for pre-paint prep but a bug for already-painted surfaces you want to preserve. Do not use TSP on painted surfaces you plan to leave untouched — it will visibly dull the finish.
Not for aluminum. TSP attacks aluminum, etching and darkening the surface. Keep it off aluminum siding, trim, and window frames. Stainless steel is generally fine; bare iron and painted surfaces should be rinsed quickly.
Rinse twice. TSP residue left behind interferes with paint adhesion — the opposite of why you are using it. After the cleaning pass, rinse with clean water, then rinse again. Some pros do a third pass with a damp sponge.
Related Internal Resources
Use these pages to compare acids, understand adjacent use cases, and route visitors deeper into the resource center instead of bouncing back to search.
Frequently Asked Questions
Visible answers that match the search intent this page is targeting.
FAQ
How much TSP do I use per gallon of water?
Is TSP the same as the "TSP substitute" at the hardware store?
Do I need to rinse after cleaning with TSP?
Can I use TSP on aluminum siding?
Need ACS-Grade TSP?
Buy Alliance Chemical's ACS Reagent Grade dodecahydrate when pre-paint prep or heavy degreasing calls for real trisodium phosphate — not a phosphate-free substitute.