History is filled with examples of financial speculators who tried to make big profits by hoarding commodities like gold, silver and copper. Now, some big users of aluminum, including Coca-Cola and MillerCoors, say that the practices of large financial institutions like Goldman Sachs have driven up the price of that important metal.

Unlike investors in the past that bought up the commodities they were trying to control, Goldman is not buying the world’s aluminum. Rather, it is storing the metal for other banks, traders and aluminum producers in a complex of warehouses outside Detroit that it acquired in 2010. The problem, as described in The Times by David Kocieniewski, is that since the bank entered this business, the time it takes buyers to get the metal from those warehouses has shot up to more than 16 months, from 6 weeks. Goldman has attributed the delays to a shortage of trucks and forklift drivers. But Goldman also pays incentives to owners of the metal to keep it in the bank’s warehouses.

Those delays have bolstered Goldman’s profits, because the bank earns more rent the longer metal stays in its warehouses. However, companies that use aluminum argue that the delays hurt them by making them wait for deliveries and can also raise the spot price of aluminum because that price is calculated by a formula that includes a premium based on storage costs. An official at MillerCoors told a Senate committee that the difficulty in getting metal supplies had cost it and other companies $3 billion last year.

Goldman Sachs says that its warehouses follow the rules of the London Metal Exchange, a commodity market that regulates the operation of a network of aluminum warehouses around the world. The bank also says that any company needing aluminum can buy the metal elsewhere, including directly from producers like Alcoa.