I'm not a metallurgist
you use a mixture of 2/3 of 50/50 to 1/3 tin
I dont weight it out or measure I just eyeball it
it also works with straight 50/50 but the bolster will become a little dull over time
I add the tin to increase the brightness and make it harder

I've been using this method to pour knife bolsters,
knife pummels and nose caps on muzzle loading rifles for over 30 years