The calcium carbonate or silica spicules of most sponges make them too rough for most uses, but two genera, "Hippospongia" and "Spongia", have soft, entirely fibrous skeletons. Early Europeans used soft sponges for many purposes including padding for helmets, portable drinking utensils and municipal water filters. Until synthetic sponges were invented, they were also used as cleaning tools, for painting, and as contraceptives. In the 20th century, overfishing is a problem. This has caused the animals, as well as the industry behind it to be close to extinction.