Several Associated Notions of Surface Smoothness

The Importance of Polishing Degree in Beer Brewing Equipment

With the upcoming beer season, more and more buddies are ready to purchase equipment, prepare for business and brewing, and consult some points of attention when purchasing equipment. However, most enthusiasts preparing to brew only pay attention to some equipment accessories. Still, they ignore the most important parameter – the degree of Polishing degree of the equipment’s inner shell (i.e., the surface roughness). Low polishing parameters can cause bacteria and foreign debris to remain, affecting beer safety and taste. Even though the surface of the equipment that is not highly polished is clean, it is still insufficient when compared with it.

We all know that as long as the beer is not contaminated, it will succeed in more than half, so having a highly polished device is very important.

Some Related Concepts of Polishing Degree:

Surface roughness

refers to the small pitch of the machined surface and the unevenness of the tiny peaks and valleys. The distance (wavelength) between two peaks or two troughs is minimal (below 1 mm). Ra is generally marked.

Surface finish

is another name for surface roughness. The surface finish is based on the human visual point of view, and the surface roughness is based on the actual surface microscopic geometric shape proposed. Because of its connection with international standards (ISO), China used surface roughness to abolish the surface finish after the 1980s. After surface roughness national standards GB3505-83 and GB1031-83 were issued, the surface finish was no longer used.

Surface finish and surface roughness have corresponding comparison tables. Roughness has a calculation formula for measurement, and the finish can only be compared with model gauges. Therefore, roughness is more scientific than finish.

Surface finish level 13Ra 0.025
Surface finish level 12Ra 0.050
Surface finish level 11Ra 0.1
Surface finish level 10Ra 0.2
Surface finish level 9Ra 0.4
Surface finish level 8Ra 0.8
Surface finish level 7Ra 1.6
Surface finish level 6Ra 3
Surface finish level 5Ra 6.3
Surface finish level 4Ra 12.5
Surface finish level 3Ra 25
Surface finish level 2Ra 50.2
Surface finish level 1Ra 100

The above surface roughness units are μm, i.e., microns. For craft beer brewing equipment, it is recommended that the roughness Ra≤0.6μm. This is because the size of bacteria is only 0.7~4μm (the size of yeast is 6~10μm). After exceeding 0.6μm roughness, the yeast may hide in this and reproduce, and eventually cause pollution as time goes by.

So how do you check whether the surface roughness of the device reaches 0.6μm or less?

There is a simple method. Before purchasing the equipment, a surface roughness comparison block is provided to the manufacturer in advance. After the equipment is manufactured, the rough surface contrast block is used for comparison inspection.

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