WASHINGTON (AP).- A painstaking conservation effort to remove old patches and repair weak spots in a 714-year-old copy of the Magna Carta has revealed that the full text of that English declaration of human rights remains intact even though some words are faded and illegible to the eye, the National Archives said Tuesday.

A $13.5 million gift from philanthropist David Rubenstein — owner of the handwritten document — is funding the conservation effort as well preparations for an upcoming exhibit.

Thanks to the gift, the largest cash donation to the National Archives, the copy of the Magna Carta eventually will be shown as a forerunner to the freedoms imagined in the U.S. Declaration of Independence, Constitution and Bill of Rights. Plans call for exhibiting it along with documents showing the struggle for rights of African Americans, women, immigrants and others.

The Magna Carta bears the seal of King Edward I and is dated 1297. It is one of 17 known handwritten copies of the text that established a tradition for the rule of law that even kings would honor. It is the only original version in the Americas, while 15 are held by British institutions and one is held by Australia's Parliament.

Ultra-violet photography revealed the previously illegible writing and a fuller picture of the document's good condition, conservators told The Associated Press. Words on the right side of the text had been hidden by water damage at some point in the past.

"It's just sort of a wonderful, magical tool that conservators use to reveal what, just to the naked eye, would seem to be lost forever," said lead conservator Catherine Nicholson. "Even though things look damaged, there's still a residue there that can be confirmed."

Low-angled light also revealed an embossed image of the king seated on his throne as part of the document's seal.

None of the faded ink was replaced during weeks of conservation because the archive abides by a conservative treatment philosophy.

"We consider it part of the history of the document, the fading, we want to leave that there," spokeswoman Susan Cooper explained.

During the treatment process, conservators removed old patches and adhesives and added handmade conservation paper to strengthen the weak spots. The Magna Carta was then humidified, flattened and will lie untouched for at least three months under weights to reach the proper moisture level before being placed in a new case with humidified, inert gas for long-term preservation.

Less than 1 percent of the document's text was illegible because of damage, conservator Terry Boone said. The missing text was not revealed under simple UV light, but only when conservators used a special camera the archives recently purchased.

"We're looking at something written in medieval hand, and it's in Latin," Nicholson said.

The future exhibit could include a ultra-violet image with the full text, as well as interactive elements with a translation to show visitors how it is linked to the rights of the Declaration of Independence and U.S. Constitution.

The first version of the Magna Carta dates to 1215 when King John agreed to have the rights of "all freemen" documented and read throughout the country. It evolved and was reissued several times until 1297 when it was entered into official English law.

Texas billionaire H. Ross Perot first purchased this document from a British family for $1.5 million in 1984 when it was last conserved at a Virginia lab. For 20 years, it was lent to the National Archives and was on public view much of that time.

Then in 2007, Rubenstein bought it for $21.3 million at auction. The billionaire co-founder of The Carlyle Group, a Washington-based private equity firm, said he bought it to prevent it from being taken out of the United States. He returned it to the National Archives in 2008 on a long-term loan.

A new gallery named for Rubenstein is scheduled to open in 2012 with the Magna Carta as a centerpiece.

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Brett Zongker can be reached at http://twitter.com/DCArtBeat