So this morning, I applied the soap to my wet beard, and carefully ran a gentle stream of tap water into my unrinsed brush -- I did this carefully because dry shaving lather is rather powdery, and can easily be shaken off the brush to float uselessly away. Then I face lathered.
My experience when re-using lather in a bowl is that the lather is slightly richer. And this face-lathering re-use was no different. Yesterday, I used mostly Grandad's shave soap, with just a bit of a non-tallow-based shave-cream sample for some scent.
Today I again used Grandad's shave soap primarily, with just a bit of tallow-based Palmolive shave stick. So tomorrow I will carefully check my brush for the tell-tale pinkish color of microbial growth, which I have observed in re-used tallow-based lather in my lathering bowl.
So far, the advice from Gillette about 95 years ago seems to be good. There are still a couple of questions to be answered:
- Does tallow-based-soap lather dry quickly enough to discourage microbial growth?
- What is the long-term effect on a brush that isn't rinsed daily?