section: Acts of vandalism
question: In what year was the painting vandalized with acid?
article: The Night Watch
candidates: On January 13, 1911, a man slashed the painting with a shoemaker's knife. The work was attacked with a bread knife by an unemployed school teacher on September 14, 1975, resulting in several large zig-zagged slashes. It was successfully restored after four years, but some evidence of the damage is still visible up close. The man was never charged and committed suicide in a mental institution in April 1976. On April 6, 1990, a man sprayed acid onto the painting with a concealed pump bottle. Security guards intervened and water was quickly sprayed onto the canvas. The acid had only penetrated the varnish layer of the painting and it was fully restored.