While the techniques used for carnival glass and stretch glass are very similar, the results have a very different appearance. Both are molded or pressed. Both are sprayed with a metallic salt solution to achieve the surface iridescence. Both were generally made at the same factories.
The main differences that set stretch glass apart from its carnival cousin is the lack of pattern, the obvious onion-skin look, and the time frame of production (stretch glass began about a decade after carnival glass and continued a few years after production of carnival glass ended). In addition, stretch glass was usually sprayed with the salts or “dope” and then shaped, while carnival glass was usually shaped before iridizing.
But despite all we’ve said above, certain carnival patterns are known with a stretch appearance and many pieces of plain or patternless glass are found with no stretching whatsoever. It is for this reason we make only a token effort to separate patterns into either stretch or carnival absolutes in this book. In point of fact, it would be impossible since carnival collectors have been claiming stretch pieces as their own for decades and we have no intention of beginning a collectors’ war with this book.
For those who are purists, we recommend they read American Iridescent Stretch Glass by John Madeley and Dave Shetlar. It is, by far, the best reference on stretch glass. Personally, we like both types of glass and have no qualms mixing them together on our shelves.
Thank you to our friends at Standard Encyclopedia of Carnival Glass