I discuss false strings in the latest June 2011 issue of Strings Magazine. Here’s the beginning of the article:
"One of the most common questions about stringed-instrument strings is about the nature of false strings. What is a false string? Musicians often use the term to describe any string that does not sound right, such as a string that sounds dead or won’t bow properly. However, a false string technically occurs when a string doesn’t produce the correct pitch due to a lack of uniformity or defects. In rare cases, the instrument itself may be the source of intonation issues.
To understand false strings, it helps to understand a few basic concepts. When we talk about uniformity, what we mean is that the string is not what physicists call an “ideal string.” An ideal string is uniform in density and mass along its length and is completely flexible. This ideal guides the choices that string designers make with materials and varieties of string design.
False strings were more common when gut was the primary string material. Gut strings are a natural product made from highly processed sheep intestines…”
Fortunately, false brand new strings are extremely rare today. However, strings can become false with use. For more details, see the rest of my article "How to Know if False Strings are Hurting your Sound." A subscription to Strings Magazine is required to access the article.