formula provided by devs :
Damage = (sqrt(phlegm / 10k) * 10) - Soak value
stone wall soak is 15. suppose your phlegm is 25(k), then
(sqrt(25k/10k)*10 = 15.81 -> rounded down to 15
15 - 15 = 0
(or, 15.81 - 15 = 0.81 -> but still rounded down to 0)
so, you're supposed to need at least 26 phlegm, but the damage you could do is only 1.
(someone at 62 phlegm did 24 damage by hand which showed as 2% per hit if my memory serves me right. which probably means damage 1 is like 0.1%, i assume.)
using a shovel should decrease the phlegm you consume (so you can bash more with less food), but does not add to your stats, is my understanding.
i always miscalculate these... need math practice seriously. tell me if i have done it wrong again.