clumpy Hysol could also just be OLD .. When it gets old, its actually more "grainy" than clumpy, almost as if sand plebes were mixed into it. The cartridges do not usually have dates on them, however the squeeze tube Hysol typically has an expiration date listed on it, and its typically good for only 2 - 3 years for optimal performance. Great deals on hysol may just be old glue at a discount FWIW.... I usually get my stuff at mcmastercar.com , never had a problem.