TSP
Trisodium Phosphate

A good paint job requires a perfectly clean surface, even if sanding and stripping isn't necessary.

Using a powerful degreaser, like trisodium phosphate (TSP), to clean and etch the surface is strongly recommended. For the last several decades, professional painters have used this product to remove dirt, grease, mildew, and soap scum from both interior and exterior surfaces.

This chemical deglosses shiny surfaces, providing "tooth" so the next layer of paint can stick.
It can also be used to clean and soften hardened paintbrushes.

Safety First

TSP is a strong cleaner and can cause irritation and even burns if used incorrectly. Wear rubber gloves, safety goggles, and long sleeves when working with trisodium phospate. Avoid letting the chemical touch bare skin or eyes.

If skin contact occurs: wash thoroughly with soap and water. Discontinue use if redness, prolonged irritation, blistering, or pain occurs.

If eye contact occurs: flush with clean water for at least 15 minutes. Seek immediate medical attention.

If ingested: DO NOT induce vomiting. Drink a glass of water or milk. Seek immediate medical attention.

It's also important to protect household surfaces from TSP splashes. Painted surfaces, finished wood, and metals can be discolored or de-glossed by TSP. Be sure to mask off anything you don't want to get damaged.

TSP Mixing Instructions

For most applications, a solution of 1/4 cup TSP per gallon of very warm water is appropriate. For very dirty or greasy surfaces (such as kitchen cabinets), increase the ratio to 1/2 cup TSP per gallon of water. For extra-strength or no-rinse formulas, read the package directions. The proportions may be different.

Using the TSP

To hand-wash the surface, use a sponge to apply the warm solution. Wring the sponge until damp and wash from the bottom up. Allow the solution to sit for two minutes to soften deposits, then scrub. Heavy buildup may require a nylon scrub pad.

Outside, TSP can be used to wash siding, fences, and masonry; apply it with a pressure washer or garden sprayer.

Standard TSP must be rinsed away with clean water; depending on how dirty the surface is, several rinses may be necessary. A fairly new invention is no-rinse TSP; it is not as strong as the original, but is well-suited for lightly soiled surfaces and general-purpose cleaning. It requires no rinsing when mixed as directed.