A 150 g soap bar made with French clay and shea butter, from Cattier — the natural cosmetics house founded in 1968 that built its reputation on clay and has been working with it ever since.
What clay actually does in a soap. Two things, both real and both modest. It adsorbs: the plate-like structure of clay minerals carries an electrical charge on its surfaces, which attracts and holds oils and particulate dirt — the same property that makes clay a good oil-spill absorbent and a good cat litter. And it provides very fine mechanical exfoliation, gentler than any scrub with granules in it.
What it does not do. Clay does not “heal” — the French argile curative and German Heilerde are traditional names, not medical descriptions, and English translations of them cause a lot of confusion. Nor does it deliver minerals into your body: the silica, magnesium and iron in clay are locked in an insoluble mineral lattice and do not cross the skin barrier in any meaningful amount, whatever the label of a clay product may imply. It is a good cleanser. That is what it is.
Why shea butter is in it. Because soap is alkaline. Saponified oils sit around pH 9 to 10, while healthy skin surface is acidic, roughly pH 4.7 to 5.5 — the so-called acid mantle, which supports the barrier and keeps unfriendly microbes in check. Every true soap temporarily raises skin pH; the skin recovers, but it takes time, and repeated stripping is what leaves people feeling tight. Shea butter is exceptionally high in unsaponifiable matter — the fraction of a fat that does not turn into soap during saponification, typically 5 to 17% in shea against 1 to 2% in most plant oils. That fraction survives the soap-making process and stays in the finished bar as an emollient. It is the single reason a shea soap feels different from a plain one.
Practical. Let it dry between uses on a draining dish — a bar left sitting in water dissolves several times faster, and this is by far the commonest reason people think a natural soap does not last.
Available at Só Verde, an organic concept store in Foz, Porto.