Paperweights are heavy an often decorative objects. Originally, before the invention of air conditioning and offices that have non-opening windows, paperweights were intended to hold sheets of paper on a surface to prevent wind from blowing the paper away. Paperweights are commonly made from glass, although other materials, such as clear acrylic, are used as well. They are often collected as examples of fine workmanship, and appreciated for their aesthetic as opposed to their utilitarian aspect. They generally are of solid glass, and have a flat base and a domed top, which acts like a lens to magnify and make the parts within move as it is handled.