Presenting her new film "Everybody Knows" by Iran's Asghar Farhadi at Cannes, Cruz told reporters that she and Bardem made a point of not taking their personal life to the set, or their work home with them.
"When I was in my 20s, I thought the more I would torture myself and the more I would stay in character for months, the better the result would be," Cruz said.
"We (she and Bardem) have very similar ways to work and maybe I did that experiment when I was younger because we both started very young."
The pair arrive on the red carpet in Cannes on May 8th. Photo:Alberto Pizzoli / AFP
Cruz and Bardem, who many celebrity watchers say have claimed the place vacated by Angelina Jolie and Brad Pitt in the star couple firmament, met on the set of the sexy 1992 Spanish dramedy "Jamon Jamon" when she was still a teenager.
But it took working together on Woody Allen's "Vicky Cristina Barcelona", which premiered at Cannes in 2008, to light the romantic spark.
Cruz took home an Academy Award for her supporting role as a hot-tempered artist in the film. She and Bardem, who won the previous year for "No Country for Old Men", are respectively the first Spanish man and woman to win an acting Oscar.
Bardem, now 49, publicly declared his love for Cruz, 44, at Cannes in 2010 and they married the same year on an island in the Bahamas owned by their friend, US actor Johnny Depp. They have two children together and jealously guard their privacy.
"I have a life and then I have my job and that allows me to jump many times in one day from reality to fiction -- I love that beautiful dance back and forth from both dimensions," Cruz said.
"It would not make your life better, I think, if you used certain things from your private life (on a film set) so the fact that we know each other and trust each other so much only helps."
Cruz and Bardem have starred in nine films together, including last year's "Loving Pablo" by Spanish director Fernando Leon de Aranoa, in which Bardem plays infamous Colombian drug lord Pablo Escobar and Cruz a journalist who falls in love with him.
Cruz said that while she enjoyed working on "Everybody Knows" with Bardem, in which they play ex-lovers thrown together decades later, "it's not something that we plan on doing every two years".
"No, that will be once in a while if we feel it's right, like in this case," she said.
Farhadi, who has frequently worked with his own wife, fellow Iranian director Parisa Bakhtavar, said the couple seemed to maintain a "healthy" distance from the industry.
"I really admired how Penelope and Javier kept fiction and reality, life and work, separate," he said.
"They are the very symbol of a happy couple and it was a pleasure to see what deep respect they have for each other."
With the sexism and abuse debate roiling the international film industry and drawing the spotlight at Cannes this year, Cruz and Bardem were asked if they were paid equally for the film. "Yes, actually," she said.
By AFP's Deborah Cole