“For the diner scene, a photograph of the building was put on a gyroscopically operated table onto which cameras had been mounted. The table was shaken and the oozy Blob stuff rolled off. When the film negative was printed in reverse, it appeared to be oozing over the building.
“The Blob was filmed in color and projected at a 1.66 ratio, then known as the ‘Paramount format’.” — from The Blob‘s Wiki page.