Like photographs, technical art is often an exception to the rule. If you are writing a nonfiction piece, you may need technical art to better explain what you are saying in the text. For instance, if you write a book on how to build a kite using household materials, you may want to use technical art to illustrate step-by-step instructions.
What is technical art?
Technical art is used to illustrate and explain specialized, mechanical, or scientific subjects based on fact. Technical art can range from diagrams to maps to instructional illustrations.
Don't worry, this doesn't mean that you need to be an accomplished artist. Often a publishing company will hire an illustrator to render the technical art based on reference material. If you believe that the inclusion of technical art will better your book, you may want to either sketch the art yourself or dig up other materials that can be used to give the artist an idea of your vision. Of course, your sketches or reference materials aren't likely to be the only thing the artist has to go on. Often the artist will also require written guidance as well as a copy of your manuscript.
Of course, it is the publisher who makes the final decision, so don't trouble yourself with finding or creating reference materials for all the technical art you think should be included. You will, however, want to include a few samples of what you plan to provide and outline in a cover letter exactly those sections of the text you believe would best benefit from the inclusion of technical art.
While it is possible that the editor will decide to take care of the reference material on her end, it is best to be prepared if you plan to propose its insertion. Again, you will present yourself in a professional manner if you show that you are willing to do all that you can to aid in the production of the book.
If this is a nonfiction work, you will be considered the expert on the matter and will most likely know best what art should be included. If the editor does decide to take on this task, you may be asked for your input and guidance. You may also be required to look over the rough artwork to okay its accuracy.
While you normally should not correct an illustrator's pictures in storybooks or other works of fiction if those pictures differ from your vision, you do need to correct a technical artist if the illustrations do not meet the requirements of the technical art. Keep in mind that rendering technical art is not an easy task, especially if the artist is not familiar with the subject matter. Therefore, keep your criticism polite and professional and do not be discouraged if there are several corrections that need to be made in the rough drawings. Just remember that whoever is illustrating your book is doing his or her best to create a spectacular children's book.