Knowledge

Why a test spot exists

A test spot is not hesitation. It is how a stain job stays honest.

Unknown finishes

Old sealer, fresh paint, and chalked metal do not all accept the same cleaner. A few inches will show the reaction.

If the orange might be iron, tannin, or fertilizer, the first chemistry that is wrong can set the stain. Testing is cheaper than that.

The rest of the wall does not get the same experiment. The recommendation changes. Sometimes the recommendation is to leave it.

The price is agreed before the hose comes off the reel.