Instructions
Check for a maker's mark. Fenton Carnival patterns made in 1970 or later feature the word "Fenton" within an oval. In 1980, numbers appeared below the name, indicating the decade in which it was made. Patterns from the '80s have an "8" stamped on them; those from the 1990s have a "9." Fenton Carnival patterns manufactured from 1907 to 1931, however, had primitive-looking paper labels. Images can be found on the Fenton website.
Examine the enamel. Fenton fired its enamel paint directly onto the glass, making it nearly impossible to rub off. Because of this, Fenton Carnival glassware decades old often appears new, despite countless washings. If the enamel is chipped and worn, chances are it's not a Fenton Carnival pattern.
Look for iridescence. The classic feature of Fenton Carnival has always been its iridescence. If your patterned glass doesn't possess that telltale metallic glow, it's not Carnival glass.
Determine the decade in which your pattern was made. Fenton first manufactured Carnival glass from 1907 to 1931. In 1970, the company began to re-issue old patterns with a new formula. If you learn your pattern was made between 1932 and 1969, it won't be considered Carnival glass.
Match patterns. Because Fenton produced hundreds of patterns of Carnival glass in varying colors, this step may take time. David Doty's website, however, displays photographs of most of these patterns. Compare your glassware to his pictures. If you have a match, congratulations.
Join a Fenton glass collector's club. These groups hold annual conventions and can provide a great deal of information regarding Fenton Carnival glass and its patterns. Consult the Fenton website for more information on these organizations.