Samuel Dufner, 37, of South Salem High School, was arrested Tuesday at the school and charged with two counts of criminal mistreatment, according to the Salem Police Department.
Dufner, who was released after posting $2,000 bail, and his attorney couldn't be reached for comment Thursday.
"The most common thing he was burning in their arms was 'I heart mom,' " said Lt. Steve Birr of the Salem Police Department.
"I have seen on social media (Facebook), though, that there were other things burned, too, like stars and stuff," Birr added.
"It all started when the teacher was doing a demonstration on how to use a Tesla coil for legitimate purposes. Then at the end of class he said you can also make markings on your arm with the coil, and he demonstrated on his own arm and then asked for volunteers," Birr said.
"We found out because a parent who was not pleased with the experiment contacted the school and the school contacted the Salem Police Department," Birr said.
Dufner was initially booked into the Marion County Correctional Facility, police said.
The school district is cooperating in the investigation, which is ongoing, and has placed Dufner on administrative leave, police said.
"The burns are like first-degree burns and fade over time. By the time we interviewed the students about the incident many of them had already faded," Birr said.
The charges stem from an incident last Thursday when several students had images burned onto their skin, police said.