Most people were taught to test a cleanser by feel. Wash, rinse, and if the skin feels tight and faintly squeaky, the product worked.
That test is backwards. The tightness is the most reliable signal in the entire routine, and it is telling you that something was taken which should have stayed.
Your stratum corneum is a barrier held together by lipids. Ceramides, cholesterol, free fatty acids, arranged between the cells in a structure people describe as brick and mortar because the analogy is close enough to be useful. Those lipids retain water. They also decide what gets in.
Sulfates are surfactants, and they are extremely effective ones. A surfactant works by binding oil at one end and water at the other, so oil that would otherwise sit on the skin can be carried away by rinsing. The mechanism does not distinguish between sebum, the day's grime, and the mortar between your own cells. It emulsifies all of it. The squeak is the sound of a surface with no lipid left on it at all, and the tightness that follows is the barrier contracting around a water loss it cannot replace at the speed you created it.
Do that twice a day for a year and you produce the condition most people describe as sensitive skin. Redness that comes and goes. Products that used to be fine and now sting. A moisturiser that stopped working, when what actually happened is that it is being asked to rebuild a barrier every morning and every night.
A cleanser has one job. Remove what is on the surface, leave what is in the structure. That is achievable, it just requires milder surfactant chemistry and it lathers less, which is a problem only because lather has been sold as evidence of cleaning for eighty years. Foam is a formulation choice. It is not a measurement.
The Setophaga Restorative Cleanser is sulfate-free and light-lathering for that reason, with eleven botanical oils including jojoba, rosehip and chamomile conditioning while it cleanses, and green tea, aloe and calendula calming skin that has spent a long time reacting to something harsher.
Thirty to sixty seconds. Lukewarm water, not hot, because heat strips lipids on its own. Then the honest test, which is not how your face feels at the sink but how it feels ten minutes later, before you have applied anything.
It should feel like nothing. That is what clean is.