Brighter, clearer beer could be on the way thanks to a superfine filter that owes its existence to the failure of a decade-old recording technology.

In the early 1990s, Philips of the Netherlands developed the Digital Compact Cassette tape format, which was designed to give CD-quality sound on standard magnetic tapes.

DCC used record/playback heads that could write or read magnetic data through holes just 70 micrometres wide. To make such small holes, Philips harnessed technology used in making microchips: it used a beam of hot fluorocarbon plasma to blast the holes in a metal film.

While DCC failed against the might of the CD, a Dutch start-up called Fluxxion in Eindhoven has now adopted the hole-blasting technology to make a new class of fluid filters.


Long and tortuous

To make their filters, Fluxxion places a 15-centimetre-wide silicon wafer disc – the sort microchips are made on – in a vacuum and uses a plasma beam to blast 3 billion 0.45-micrometre holes through the wafer. The wafer is then rinsed.

The ultra-fine filter is a boon to brewers who need to remove cloudy yeast residues. Conventional beer filters are made of either densely packed fibres or a dusty material called kieselguhr, which consists of fossilised hard-walled algae called diatoms.

In each case the passages through the filter are long and tortuous, and vary enormously in width, so they can demand pumping pressures nearing 1 atmosphere. But the silicon filter has short passages of consistent and precisely controlled size, so the pumping pressure need be only around one-tenth of an atmosphere.

Filter bacteria

To test the silicon filter, the Bavaria Brewery of Brabant in the Netherlands, gave Fluxxion cloudy barrels of freshly brewed beer to try filtering in the lab. The beer cleared so well that Bavaria installed its own pilot plant eight weeks ago.

“The brewing industry wants to phase out kieselguhr in any case because the dust is a health risk unless carefully handled and disposed of,” a Bavaria spokesman says.

But beer is not the only target for the filter. Fluxxion is testing it on milk to see if it can filter out bacteria and thus avoid pasteurisation, which can impair the taste.

The firm is also experimenting with filters with 0.2-micrometre holes, to see if they can remove viruses from blood plasma.