How can you determine if SP-207 is no longer usable?

To determine if SP-207 is no longer usable, observing whether it has gelled and/or expired is crucial. The gelled state indicates that the product has likely undergone a chemical change that can affect its application and effectiveness. Additionally, checking the expiration date is essential, as using expired materials may compromise the quality of the work being performed. A product that has crystallized or gelled may not adhere properly, leading to potential failures in repair or installation. This makes option B the most reliable indicator of the product's usability.

While strong odors or changes in color might suggest a problem with the product, they are not definitive indicators of usability like gelling or expiration. Similarly, a product being too thick could be a result of improper storage but does not necessarily confirm that it has reached the end of its usable life. Therefore, focusing on the state of the material (gelled) and its expiration provides the most accurate assessment of its usability.