There are great unholy gobs of olive oil 'Castile' soaps on Etsy.
The soap doesn't matter as much as the tanning. We've known one basic fact since World War 1: veg tan leather falls apart when water is allowed to soak in. Which is why we invented chrome tanning.
Have you actually tried my carpet/upholstery foam on a nitrile glove trick? Foams -> minimal wetting, maximal defunk.
Muc-Off took the carpet foam idea and ran with it to make Foam Fresh. Carpet foam for sports.
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But they f*cked the fragrance part: way, way way stronger than it needs to be, headache inducing levels.
Mind providing more detail on the carpet foam process? I'm intrigued...