Use of scratchable ink
An opaque ink that can be scraped to discover a visual. The most opaque are Silver, Gold and Black.
To be rubbed:
Available in all ranges of inks, Silkscreen, flexo and gravure. White ink that gets gray when rubbed with a coin.Se declines in all ranges of inks, screenprinting, flexo and gravure.
Autonomous: ink range that colors with friction (red, blue, black) or scratch (ink with water)