Someone explain me some math..

[lastlight]

Originally Posted by don.ald

1 drop of c = 50. so when you get to say 400 and the colour has not changed switch to D. +10
so 8 drops of c = 400 then add on drop of d and if it changes then your ca is 410. if it takes 2 drops of d to change colour then its 420, and so on.

+1

I usually add 7 drops of C (350) and then switch to D so as to not over-shoot the mark. If all goes well I add 7 drops C (350) + 7 drops D (70) = 420