In 1976, in Cleveland Ohio, CAL-OSHA performed an impact safety test on several products, by mounting the windows into a box placed below the slag pit trough and poured molten slag onto the different product.
The red-hot steel slag can still be seen all around the box. Of all ten products tested, MacPherson & Company’s SAFE-SHIELD composite glasses was the only product that passed this CAL-OSHA test.