Using Text of Operas ... in Paintings

Dear Rich (and Dear Rich Staff): I have created painted works of art with oil on canvas and water color marker on paper using the text of public domain operas and plays in such a way that they are no longer readable as text. The full text is still there but, it has been over written in a variety of colors such that one could not actually gain any context or meaning from trying to read the painting as a copy of the opera or play. I judge that this as fair use and should be able to sell my work without consequence. Do I need to get permission to use copyrighted work that has been similarly obscured for this purpose if I intend to sell the unique painting I have created? Just an FYI, but you state you're using the text of public domain operas. If the text of the opera is in the public domain, there's no need for a fair use argument -- you can do whatever you want with it. As for your question about the use of copyrighted works there are two ways that could play:

• If you purchased the text of the opera -- for example, in sheet music form or in a book -- and you are painting on the pages of text (or incorporating them a collage), you won't need permission. You can probably justify that under the first sale doctrine. 
• If you are reproducing the text in a painting, we think you can probably make a strong fair use argument because you are using a small portion of the opera's text, you are not competing with or depriving the copyright owners of commercial gain, and based on your description, your use appears to be transformative --  that is you're making a new statement. if the words are obscured so that their meaning cannot be ascertained, we're not even sure you've infringed as your artwork no longer would be substantially similar to the opera text. Check out fair use rules before proceeding.