There are a few things which I don't understand.
a) עפצים and קנקנתום are argued by some Poskim to be mandatory in ink because they are mentioned in the Gmara or Rishonim. There are, however, other ingredients, like עשן פחם דבש אדרמינט שמן , which are also mentioned in the Gmara or Rishonim. עשן is the most favorite blackening ingredient amongst the Rishonim and Achronim. Yet, these other ingredients are not considered mandatory. How come?
b) The קנקנתום which is argued by some Poskim to be mandatory in ink, is a natural material mined from the ground. Nowadays this natural קנקנתום is difficult to obtain. As a substitute, ink manufacturers in Israel have replaced the natural קנקנתום with much cheaper synthetic iron-sulfate. קנקנתום and synthetic iron-sulfate are not the same material, and, the synthetic iron-sulfate is definitely not the natural קנקנתום of חז"ל . (Natural קנקנתום contains iron-sulfate plus other ingredients. Synthetic iron-sulfate also contains contaminants which are not found in natural קנקנתום .)
A few years ago I asked someone in Israel to ask a famous Rav, who is a great expert in STAM, about this switch to synthetic iron-sulfate. The Rav was shocked to hear it, and I was told that his face turned white. The Rav did not give any answer. Now the question is: If the natural קנקנתום of חז"ל is a mandatory ingredient, then, who permitted the ink manufacturers to replace it with a synthetic substitute? And, if this replacement was permitted, then, how can natural קנקנתום be mandatory?
c) Of all the ingredients that are mentioned in ink, עפצים and קנקנתום are the only two ingredients against which there are opinions in the Gmara or Rishonim that prohibit them or consider them פסול . How is it possible, then, to argue that ink must contain these two ingredients, and that the ink which contains these two ingredients (plus goma) is the most Mehudar? Isn't it the same as arguing that חלב עכו"ם (which is considered Treif by some and Kosher by others) is the most Mehudar milk, or that non-Shmura flour is the most Mehudar for baking Matzah?