Most of the time old sets of encyclopedias are worth nothing. If the sets are very old there might be some artistic quality in the old pictures that are in them. For instance pictures of cities in the 1800's or even more recently. These pictures could be cut out, enlarged and put in frames. Especially pictures of places that have changed or no longer exist. I am not sure about copyrights pertaining to them but if they are for your own use or for children's projects and not for selling it probably would be fine.
By Lilac from Springfield, MA
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Since old encyclopedia sets are hard to sell and no one has the space for them anymore, individual volumes make great "birthday" or event cards. Give the volume that is the initial of the person ...
Although old encyclopedias don't typically have value as reference books, they are sometimes of value to crafters. This is a page about donating old encyclopedias.