Daniel Wallace, 33, and Kacey Adams, 34, broke in to their home in London Road, Halstead, in April 2016.
The victims, aged in their 60s, were tied up, had boiling water from a kettle poured over them and they were threatened with a knife and hot iron, Kent Police said.
Wallace and Adams will be sentenced at Maidstone Crown Court at a later date.
The couple were left tied up when Wallace and Adams left with cash and jewellery.
The man managed to free himself and alerted police. Both victims were taken to hospital with serious injuries.
The woman suffered about 30% burns and required treatment in an intensive care unit for several months.
Adams, of Covert Road, Hainault, Ilford, and Wallace, 32 and of no fixed address, were arrested on 31 May at Heathrow Airport, on their way back from a shopping trip in Dubai, police said.
Det Insp James Derham said: "Adams and Wallace were responsible for crimes which can only be described as barbaric and cruel beyond words.
"The elderly woman had two kettles of boiling water poured on to her, inflicting horrific burns and injuries, which could quite easily have proved fatal.
"The psychological scars that both victims are continuing to deal with are unimaginable."
Two men have pleaded guilty to beating a couple and dousing them with boiling water during a burglary.