Section 2-315 of the UCC creates another implied warranty. Whenever a seller, at the time she contracts to make a sale, knows or has reason to know that the buyer is relying on the seller’s skill or judgment to select a product that is suitable for the particular purpose the buyer has in mind for the goods to be sold, there is an implied warranty that the goods are fit for that purpose. For example, you go to a hardware store and tell the salesclerk that you need a paint that will dry overnight because you are painting your front door and a rainstorm is predicted for the next day. The clerk gives you a slow-drying oil-based paint that takes two days to dry. The store has breached an implied warranty of fitness for particular purpose.
Note the distinction between “particular” and “ordinary” purposes. Paint is made to color and when dry to protect a surface. That is its ordinary purpose, and had you said only that you wished to buy paint, no implied warranty of fitness would have been breached. It is only because you had a particular purpose in mind that the implied warranty arose. Suppose you had found a can of paint in a general store and told the same tale, but the proprietor had said, “I don’t know enough about that paint to tell you anything beyond what’s on the label; help yourself.” Not every seller has the requisite degree of skill and knowledge about every product he sells to give rise to an implied warranty. Ultimately, each case turns on its particular circumstances: “The Convention provides (Article 35): [The goods must be] fit for any particular purpose expressly or impliedly made known to the seller at the time of the conclusion of the contract, except where the circumstances show that the buyer did not rely, or that it was unreasonable for him to rely, on the seller’s skill and judgment.”