Final answer:
The xerography process used in modern copy machines is the method utilized to reveal text from indented impressions.
Step-by-step explanation:
The machine used to reveal text from indented impressions is based on the process of xerography.
Xerography is an electrostatic printing process that can be used to detect indented writings. It utilizes the principles of electrostatic charges to attract toner particles to the areas where impressions are present on the paper. This method is particularly useful when one needs to visualize indentations made by writing instruments that may not have left visible ink but have created an impression in the paper.
While the detailed process you mentioned involving the acid, resin powder, and inking to create an impression pertains to a different type of printing called intaglio, xerography is the more relevant method for revealing indented impressions left on paper, commonly used in modern copy machines.