Q: When I buy glue, I can’t find a production or expiration date on the containers.
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glue code 1
The code on a bottle of nTitebond glue that wasnmanufactured in July 2002.

Q: When I buy glue, I can't find a production or expiration date on the containers. It could have been sitting in the store for years—how do I know how old it is?

Dave Starr, Zumbrota, Minn.

A: Dave, the answer is right there on the glue bottle—once you know the code. Here's how to interpret the line of numbers and letters stamped on the containers of white, yellow, and polyurethane glue produced by Franklin International, maker of Titebond and the biggest supplier of woodworking glue.

In the typical code shown above, the first number represents the final digit of the year in which the glue was produced; it's followed by a letter designating the month, with "A" standing for January, "B" for February, and so forth. (They skip "I" because it looks like the number 1.) You can ignore the rest of the code, which relates to the particular batch of glue.

Elmer's glue carries a similar code. In this case, however, the series starts with a letter corresponding to the year of manufacture, with "H" standing for 2005 and "I" signifying 2006. The two numbers following tell you the day of manufacture, and the next letter reveals the month, with "A" designating January, etc.

Now, what should you do with that information? According to Franklin spokesman Dale Zimmerman, white and yellow glue have a shelf life of two years; polyurethane and liquid hide glue have a one-year shelf life. Note: Franklin's hide glue carries an uncoded expiration date to make sure everybody can read it. That's because degradation is a greater problem with this type of glue.

If your retailer removes the code, look elsewhere for that bottle of glue. When you take the glue home, write the date of purchase on a piece of masking tape and place it on the container as a clear reference to the glue's age. Then store it out of direct sunlight.

glue code 2
You see the worst-caseresult of keeping yellowglue too long.