I’m on well water that is extremely hard. 1. I’ve found the key is to start with shaking almost all of the water out of the brush.A lot of this has to do with the water itself. Soft water has lower levels of magnesium and calcium. You can get a water tester that tests PPM or TDS (parts per million) or (total dissolved solids). If you are in the 400-600 TDS range I would say it's likely the water. If you don't want to spend the money on a tester, if you have a water filter like a Brita or a Zero Water on hand, I would suggest trying it with that water. If this solves the problem you can get a water softener for your house (highly suggested just for general health and skin) or you can install an ion exchange filter for your sink to soften it up a bit.
This is the same process that water softeners use, which is why the salt is not actually added to the water, but rather replaces the material needed in the resins for the ion exchange process. This is why a high efficiency water softener is important. You can install one yourself for about 400 bucks with some hunting, you'll use about 10 bags a year with a HE unit. Not all TDS is bad or bad for you, but having less never hurts, and I bet it might help your lather.
City water, well water, and aquifer water can all make a difference. Different water treatment plants add different amounts of chemicals and have different treatment methods. With my limited experience and the project I did in one of my wastewater classes, city water is higher in contaminates than other methods. You can view your specific water quality report (which is another alternative to buying a tester) to see the quality of the water for your area, which is public record.
I have Stirling Margaritas in the Artic, and it lathers like a dream with soft water, and really takes some work using the same brush before installing a water softener. I hope this helps a bit.
2. I bloom the soap, I hard press it and spread it out on the bottom of my bowl. Sprinkle a small amount of hot water .
3. I soaked my brush in warm water for about five minutes.
4. I Dump the bloom water.
5. Take the brush out of the warm water shake out the water , gently squeeze the remaining water from the brush.
6. I then begin to work on creating lather, starting in circular motion, switching between clockwise and counter clockwise.
7. When a paste begins to develop, I incorporate a back and forth motion with the circular motion.
8. Now I add a few drops of water and continue the back and forth motion and circular motion.
9. Now the lather begins build and it’s time to be more generous with the amount of water I ad.
10. I continue the back and forth motion and circular motion and ad a couple up and down motions (I don’t smash the brush down or splay it) just a couple up and downs.
11. I add more water, I’m always amazed at how thirsty the soap gets at this point. I keep going and add water until I see a sheen in the lather and there’s almost no bubbles.