plating, anodizing, & finishing Q&As since 1989
Why don't my 18-8 finish washers shine?
February 6, 2012
Q. I have a refurbishing project that requires #4 stainless finish washers that are fairly shiny. I have ordered #4 18-8 finish washers from two different sources and have been disappointed in the quality of the finish on them. By this I mean they don't have a shine that is close to chrome as I am used to seeing in others I have purchased.
So the question is what causes stainless to shine more? I have read articles on 18-8 and also 316 but they don't mention the quality of the finish only the corrosion resistance and hardness of them.
- Atlanta, Georgia, USA
February 7, 2012
Hi, Bill. A bright white wall reflects the same amount of light as a mirror does, but it looks very different, and the difference is called specularity. When light hits a mirror, "the angle of reflection equals the angle of incidence", and the patterns of the incoming light are retained perfectly in the reflection. The white wall offers a fully diffuse reflection, with the light bouncing back equally in all random directions.
The reason your washers don't exhibit full specularity is that they are not mirror smooth and tiny bumps reflect some of the light at the wrong angles and you partially lose the reflection. Polishing and buffing to a mirror finish is time consuming and expensive unless it's your own labor, but you can do it yourself. Please search this site for "mirror polishing of stainless steel". Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey