Homeland Security Secretary Kristi Noem said Tuesday that President Donald Trump has directed the Department of Homeland Security to paint the entire U.S.–Mexico border wall black. Speaking beside a section of the barrier in Santa Teresa, New Mexico, Noem told reporters the darker coating will absorb heat, making the steel panels painfully hot to touch and therefore harder to scale. Noem added that the paint is expected to slow corrosion and extend the wall’s lifespan. The secretary did not give a cost estimate or timeline for repainting the hundreds of miles of existing barrier but said work has begun, reviving a proposal first tested near Calexico, California during Trump’s first term. Funding for the project comes from a border-security bill Congress passed in July, which Noem said is also financing new cameras, sensors and other surveillance equipment. DHS crews are currently erecting about half a mile of new wall each day, and the department is evaluating similar measures for the northern frontier, she said.