Watch Plating 101 Primer 01 02 03 04 05 06 07 08 09 10 11 12 13 14



factor 2 - Hardness of the Gold Plated Layer: Its not enough to have a thick goldplated layer if it is easily rubbed off from casual contact with clothing, skin and other surfaces. If the gold plating is soft it will be easily worn off over a short period of time. This will be especially noticeable around the high points of the watch and the primary edges near the lugs. Surface hardness and toughness of the final gold plated layer is extremely important for the watch to be resistant to scratches and incidental abrasion.

Unlike goldplating thickness, hardness for goldplating is no longer regulated or specified by the FTC (as of august 1999). The manufacturers within the watch industry have technical guidelines for recommended hardness that are still utilized on newly manufactured goldplated watches.

Commercial electroplating shops who goldplate objects such as plumbing fixtures will defer to Military Specifications for finish hardness specifically MIL-G-45204C. In that specification, hardness for goldplating is referred to as "grade" (see chart e). For our replating applications, we will rely on this aspect of this specification for determining the standards for the different levels of hardness available for gold plating of watches.

The standard for measuring the hardness of gold plating is expressed as "knoop hardness". Knoop hardness is calculated by measuring the indentation produced by an elongated four-sided pyramid shaped diamond point. Pressed into an electroplated surface under loads (usually less than 1 kilogram-force) the indenter creates a 4 sided impression. Hardness numbers are cited relative to specific load values that were used in the test.

A knoop hardness value for a replated gold watch should be rated at least 110-130 range (grade b).

This hardness value will provide good scratch resistance and long term finish durability for watches. You could designate a harder finish, however the tendency toward embrittlement of the goldplating can become an issue. In some cases this could lead to minor chipping of the heavy goldplated layer, particularly on the sharp edges and prominent design contours of the watch.

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