Adding glycerin to shaving soap--how much is too much?

[SomethingGoodAustin]

Hey there;

I know most shaving soap makers add at least 10% glycerin ppo to their shaving soap to improve lather stability. I was wondering if anyone has tried adding it in a higher amount, and if so, what happened? I notice that Mama Bear Shaving Soaps mentions their soap has 20% glycerin (although I don't know whether that's actual amount added to the soap, or what's naturally in there, or something in between).

Would a higher percentage of glycerin spoil the lather?

Thanks in advance!