Some products, such as yogurts and nut butters, are often packaged in plastic with an aluminum seal, either the metal alone or a thin aluminum layer on a paper backing. I’m assuming these are applied using heat, to melt the plastic just enough for an airtight seal.
The problem becomes apparent when it’s time to remove the seal in order to make use of the product. Either the seal removes effortlessly, easily, or with difficulty, that last often in pieces (potentially very messy pieces in the case of nut butters) and often with pieces of the seal remaining stuck to the top of the jar, preventing an effective re-sealing.
An effortless removal means the heat seal didn’t work; it was either not attempted, or the equipment malfunctioned. This is rare, but I’ve seen it more often on nut butters than with yogurt.
An easy removal means that it offers some resistance, but peels off completely and usually in one piece. This is the case I almost always find with Lucerne (Safeway) plain whole-milk yogurt, the only kind I generally buy. The surface of both the aluminum and the top of the container where it binds both have a mottled texture, which is what I consider the most likely reason for the ease of removal.
Trader Joe’s peanut butter, and Costco’s Kirkland brand organic peanut butter and almond butter, all have the messy, difficult to remove, aluminum-coated paper seal. It’s probably better to cut with a knife along the inside edge of the plastic jar, but they provide a small tab with the suggested use of lifting to remove the seal, and I always do, to my regret.
Obviously, I don’t have the domain knowledge to state unequivocally what the best practice is, but as a consumer I can say that Lucerne Dairy has a better handle on it than do Trader Joe or Costco. I suggest some communication, or failing that, perhaps some industrial espionage, is in order to improve the state of the art.