The secret to his longevity and good humor in 30 years in the Family Division of Allegheny County Common Pleas Court, as Judge Lawrence W. Kaplan tells it, has been his "magic slate mind."

A day's worth of divorce and custody cases carries enough heartbreak for several lifetimes, so long ago Judge Kaplan learned that when he was walking the courthouse halls or heading home to his wife, Natalie, he had to cast the details of his day aside and wipe the slate clean.

"There's no way," he said, "you can carry around with you all the sadness and anguish that takes place here."

Judge Kaplan himself, though, will not be forgotten so easily.

Today is his final day on the bench, as the 80-year-old senior judge has reached the state's mandatory retirement age, but his presence will remain -- and not just because his portrait is displayed on the fifth floor of the Family Division courthouse.

Colleagues and friends said Judge Kaplan's slate is inscribed with a slew of accomplishments and causes he championed -- most prominently, the use of mediation outside of court to solve disputes -- but also his playfulness and kindness.

And in setting up shop in the Family Division for three decades, he helped turn what was considered a stepping stone to a place where judges have committed to long terms.

"For many of the judges, it's where they start and they can't wait to get out of there, but he's been there forever, it seems," said Judge Eugene Strassburger, who began with Judge Kaplan in Family Division then later moved to Civil Division.

"It's now become a career choice that is acceptable for anybody in the judiciary."

Upon his appointment to Common Pleas Court in 1978, Judge Kaplan seemed an unlikely candidate to stay in Family Division for long.

The Uniontown native, who graduated from University of Pittsburgh Law School in 1953 and spent three years in the Army Judge Advocate General Corps, had done tax, estate and business law in his private practice. His background was suited to Orphans' Court, but Judge Kaplan quickly found he had a knack for divorce and custody cases.

"I think what I'm doing here is important work," he said this week, reclining among stacks of boxes in his office. "I felt I was contributing by doing it. And I thought I was pretty good at it."

He became involved in several organizations dedicated to improving the practice, serving as president of the Association of Family and Conciliation Courts in 1988-89. In addition, he gained a reputation for having an even temperament and ability to finesse a case to resolution.

Carol McCarthy, a veteran attorney in the Family Division, said when Judge Kaplan is assigned a case, typically he will bring the lawyers in for a conference.

He listens as the lawyers argue back and forth, then he will contemplatively rub his face and head, and offer a solution that finds the middle ground.

"If that doesn't solve the case," Ms. McCarthy said, "usually it's enough direction that you can get the case resolved."

In fact, Judge Kaplan preferred being bypassed altogether en route to a resolution.

In the early 1980s, after attending a conference on the subject in Philadelphia, he began advocating for mediation, a process in which the parties meet and try to find a solution without the strife and cost of the court system.

Judge Strassburger described his initial reaction to the program as "skeptical."

"Can you really make the horse drink after you led it to water?" he thought.

But mediation has flourished and expanded into civil court, where Judge Strassburger, that division's administrative judge, said he's seen a measurable reduction in caseloads because so many medical malpractice suits are solved that way.

Divorcing couples are now required by law to be schooled in mediation; Judge Kaplan testified in support of the measure in Harrisburg.

Among the trinkets left out in Judge Kaplan's office was a button bearing the words: "Mediate Don't Litigate."

As the founder and president emeritus of the Mediation Council of Western Pennsylvania, it's an issue that is dear to his heart and a linchpin of his legacy.

"He's like the father of mediation in Allegheny County -- and maybe the state," Judge Strassburger said.

Beyond causes and committees, the Kaplan slate is colored by his bright personality.

A noted cut-up, Judge Kaplan is quick with a self-deprecating joke about his hair -- or lack thereof -- willing to dress in drag for skits at the Bench Bar Show and can always be found on the dance floor at parties.

At work, he can brighten anyone's day, colleagues said.

"He's really truly been a mentor to all of us," said Kim Berkeley Clark, administrative judge for the Family Division. "He's probably one of the most beloved judges that we've ever had."

That's why a big crowd is expected for his going-away party today -- declared Judge Kaplan Day by Mayor Luke Ravenstahl -- but he's hardly retiring. Unlike most judges his age, he has kept nearly a full caseload for the past 10 years as a senior judge, and he's only leaving because the state requires it.

As he exits the courthouse, Judge Kaplan is moving just a couple blocks over to Rothman Gordon law firm to continue his work as a mediator and a mentor.

"I think I have a little wisdom they can ooze out of me," he said.

Longtime friend Paul Titus, who practiced law with Judge Kaplan before he moved to the bench, said, "He's one of those people who will work as long as he can work."

And in the process, he'll add yet more to a slate that won't be wiped clean.