Silverware Burnishing

Previous posts about the basics of silverware burnishing (Part 1 and Part 2) described the process through which silverware and flatware are restored in a barrel tumbling process. The basic outline described the flowing of the metal to 'fill' the scratches and the removal of the oxidation on the surface. Below is a picture showing an extreme example of what can be accomplished.

Silverware Burnishing Test Results

• Far left - Before sample with heavy oxidation, scratches and some pitting on the surface
• 2nd from left - Tumbled in Steel Media and a polishing compound. Sometimes testing is required to determine if the combination of media and compound will discolor the surface even though the process removed the scratches and pitting.
• 3rd from left- Tumbled in steel media with an alternative compound. While it is difficult to tell, both the 2nd and 3rd pieces are similarly polished The proper compound (for this application) clearly resulted in a brighter, polished finish.
• Far right - Tumbled with the same compound as the 3rd part but with a Precision Ceramic polishing media. The surface is clean and bright but not quite as good as the Steel Media. This process would be best if the tumbling equipment being used is not designed for heavy media.

Silverware Burnishing Basics - Part 2

The purpose of silverware burnishing is to both physically and chemically clean and smooth the fine surface 'grains' of the metal. This is accomplished through the use of a barrel tumbler and the appropriate tumbling media and compound.

Stainless steel burnishing balls (media) are used to force the metal to 'flow' and fill the scratches on the surface. As the entire load is rotated in the barrel, the media lifts up the back side of the the barrel and cascades towards the front. As the parts are carried with the media in the sliding area, the weight of the burnishing balls impact with the surface of the silverware. This contact forces the metal to fill the low spots and even out the high spots.

In combination with the physical polishing, the water and burnishing compound help to remove the tarnish (silver sulfide) and keep the process lubricated. Using the proper compound (and changing the solution regularly) will limit damage to the silverware in process and keep re-deposition to a minimum.

The combination of chemical cleaning and microscopic, physical manipulation leads to a bright and polished surface finish.

Silverware Burnishing Basics - Part 1

Silverware burnishing is a process that combines surface hardening and polishing without the use of abrasives. On a microscopic scale, a metal surface is actually composed of tightly packed individual 'grains'. The basic theory of burnishing is that these surfaces can be hardened and shined through the manipulation of these grains.

Over time and normal use, silverware is scratched and tarnished with a thin residue of silver sulfide. This results in reducing the polished surface finish and texture. The burnishing process is designed to restore the silver surface through a barrel tumbling process. This process forces the metal to 'flow' and physically fill the scratches. At the same time, the burnishing process chemically removes the tarnish.

This combination of chemical cleaning and physical compaction results in a shiny, hardened surface that improves the surface appearance and increases the lifetime of the silverware.