Ashtangasamgraha 39.9

39.9

In the case of the mild [caustic], he should extinguish the stones and the like and remove them, but he should not grind and add them.
In the case of the sharp [caustic], however, dantī, citraka, lāṅgalikā, pūtīka sprouts, tālapatrī, biḍa, svarjikā, kanakakṣīrī, hiṅgu, vacā, and ativiṣā, finely powdered, and calcined conch shells and oyster shells, should be added as an additive as before.
And these should be applied after seven nights according to the strength of the disease.
If its strength has waned, however, he should add caustic liquid again to strengthen it.
There, not excessively sharp, not excessively mild, white, smooth, fast-acting, slimy, forming a peak, easily extinguished, causing little pain, and non-clogging: these are the ten qualities of caustic.
And the faults are also ten.
They are as follows:
excessively hot, excessively cold, excessively sharp, excessively mild, excessively thin, excessively thick, excessively slimy, spreading, deficient in drugs, and deficient in cooking.