Drops are an inaccurate measurement since dropper size, temperature, etc... can all impact this.
I would recommend pigmenting between 0.5% and 2% by weight or volume (both pigment blends and resins are in the 1.1-1.2 density range, which is close enough to be the same between weight and volume at these levels) when using a highly concentrated pigment.
Most highly concentrated pigments are pastes which are dispensed by syringe and not dispensable via dropper.
What kind of pigment are you using?
How much ml is a drop of FTD pigment?
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