— NASA is holding a "baked-goods" sale for schools, but instead of tasty desserts, the space agency is offering something much hotter: space shuttle heat shield tiles.

NASA began Wednesday offering 7,000 of the black and white lightweight tiles to U.S. schools and universities that "want to share technology and a piece of space history with their students."

The tiles are free for the asking but following the "transfer protocol" for government property, schools must cover the shipping and handling charge — a grand total of $23.40.

That's quite the sale considering that NASA estimates its original acquisition cost was $1,000 per tile.

According to the tiles' manufacturer, Lockheed Martin, the baked silica squares originally cost NASA about $10,000 per square foot installed. Typically, tiles measure about a quarter of that or six by six inches (15.2 by 15.2 cm).

More than 20,000 tiles are installed on each space shuttle and each tile is designed to survive 100 trips to space and back. Varying in thickness from one inch (2.54 cm) to five inches (12.7 cm) depending on the heating they will be subjected to, the tiles collectively protect the orbiter from temperatures as high as 2,300 degrees Fahrenheit during its reentry into the Earth's atmosphere.

The silica tile material — referred to as LI-900 or Lockheed Insulation-9 pounds per cubic foot — insulates heat so well that tiles can be held bare handed on one side even while the opposite side is still red hot.

Educators can demonstrate that ability in the classroom, substituting a blow torch for the reentry-generated heating.

NASA is fulfilling the requests for the tiles on a first-come, first-served basis. Qualifying educational institutions apply online through the General Services Administration (GSA) website.

A part of NASA's on-going efforts to "preserve the shuttle program's history and inspire the next generation of space explorers, scientists and engineers," the heat shield tile offer comes as the space agency is preparing to retire its orbiter fleet next year. Two more missions are scheduled, with a third pending Congressional funding.