As I indicated, my skin is too sensitive to work the lather on my face.
Some people say start with just a little water, make a thick paste, and then add water a few drops at a time until it is properly hydrated. I do not do that.
Here is my procedure for most soaps other than creams, croaps, very soft artisan soaps and hard tallow pucks. I will note the differences later.
I start with 1 Tablespoon (15 ml) of hot water. I pour it into the soap tub and swirl it around for about 10 seconds until the liquid becomes slightly milky. I then pour the bloom water into my shave bowl. (Note: I do not do this with creams or soft croaps, but I do with firmer soaps). I soak my brush, squeeze out excess water and then shake the brush four time to remove as much water as I can, leaving the brush damp, but not wet. Then I load the brush for about 7-10 seconds.
My lather bowl is the mortar bowl from a mortar and pestle set. The bottom is designed for grinding, so it is somewhat rough. It is an ideal surface for building a lather quickly. I stir the brush vigorously in the bowl until all the larger bubbles are gone. For some of my better soaps, that can occur in 30 seconds. If the soap takes more than 60 seconds to lather, I won't use that soap again. If I load too little soap, the lather may be too thin and I will need a could of more swirls in the tub. More often than not, I will need to add a few drops of water.
My procedure makes enough soap for about five passes. I do a four pass shave plus do a fifth bonus lather after the shave to condition my skin. If you do not need that much lather, you can reduce the amount of soap and water used.
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With creams, croaps, and soft soaps, I do not bloom the product. I will scoop out about a rounded 1/4 teaspoon of product (about 1.5 grams) and add that either to the bowl or to the brush. Some people say that is about the size of an almond.
Hard tallow pucks do best if you use them every day. I have a large number of soaps in rotation. The pucks dry out between uses, so I am not a fan of hard pucks. When I do use one, I will allow it to bloom for at least 30 minutes and perhaps even overnight.
BTW: I refuse to use Williams Mug Soap as I have found that it takes a minimum of two minutes of lathering time. Some say that it produces a good lather if you work at it, but I refuse to put that much effort into lathering a soap. When I have numerous soaps that will lather in 30 seconds, why would I use a soap that needs two minutes or more of effort?
Some people have found my test for proper lather hydration to be useful. While shaving, I fill my sink up with water and leave the water trickling. If you live in a water restricted area, you can do this with a small bowl or glass to minimize water use. As I shave, I dip my razor gently into the water, no swirling. If the lather sticks to the razor, the lather is too thick and you need to add more water. If the lather immediately releases from the razor and disperses, the lather is too thin. If the lather releases easily from the razor and floats to the surface as a cloud of lather, the hydration is suitable. Some soaps will have a narrow range of hydration; some will have a wider range. Within that range, you may prefer a slightly thinner lather that provides more slickness and less cushion, or a thicker lather that provides less slickness and more cushion. I try to get a good balance of both slickness and cushion.