Stationed in the engineering department some time back, this editor noted that the mechanical engineers, and especially the engineering director, could get a bit dreamy-eyed when the subject turned to stainless steel.

That same kind of feeling for the utility and beauty of the materials sciences was still alive and kicking at Interphex, held in April in New York City’s Jacob Javits Center. As is well known, stainless steel is widely used in pharmaceutical processing for aseptic and silicone applications.

“I love all of it, to tell you the truth. Stainless just catches the eye,” said Craig Bell Jr., a representative with Alloy Products Corp. of Waukesha, Wis. (“Stainless steel craftsman since 1929,” reads his business card.)

“I was on the shop floor and learned about it there and now I’m working with customers,” said Bell. What’s important to his pharmaceutical industry customers, he says, is the durability of stainless steel and its compatibility with a wide range of substances.

“It’s the durability,” said Pat Cuneen, BioPharm product manager with MKS of Boulder, Colo. “The only ‘enemies’ stainless has are bleach and salt. It’s 316L that’s the most used, and of course there’s hastelloy, while 304 isn’t suitable for wetted applications.”

Since the end of World War II, the general trend across many industrial markets is the substitution of plastics for steel applications. Pharmaceuticals are no exception, with growing use of so-called single-use technology, which substitutes plastic liners for stainless steel.

Yet, says Cuneen, stainless remains popular despite the growth of single-use technology, with some of the major pharmaceutical companies hesitant to embrace it. In general, stainless is considered suitable for large batches and sustained production, while single-use is most needed where the most flexibility is needed.

But “it’s not an either-or question,” said Mani Krishnan, a director with EMD Millipore, “you see both stainless and single-use in this booth. If you’re making 50 batches a year of the same thing, you don’t need single use, even at a small scale.”

It’s a question, rather, he said, of what the user’s pain point is. Pharmaceutical companies have multiple products in the pipeline, at different phases of development. For example, “a pilot plant for proteins and vaccines may be asked to produce 50 grams of a given molecule in three month’s time. Its next project could be a different molecule in a different phase of development.”

As to the aesthetic quality that so many people see in stainless steel as opposed to plastics use, Krishnan has a trenchant reply: “The hansom cabs in Central Park here in New York City are aesthetically pleasing, but you wouldn’t want to ride one to work every day.”

And in fact, Krishnan sees plenty beauty in the development of plastics use in pharmaceutical processing, using as an example a single-use chromatography system that manages fluid flow with a kind of template inspired by the printed circuit board. “It’s very different than a multi-use system in its design, delivering the same quality performance with the benefits of single use.”