Karatclad is a term, used by various jewellery designers, meaning heavy gold plate.
Information provided by goldsilverpro on goldrefiningforum.com:
“I used to work for Sel-Rex, the company that owned the Karatclad trademark. Sel-Rex sold gold plating systems and licensed their customers to use the Karatclad stamp. To use it, they had to guarantee 100 microinches of plating. Most all the plating used is at least 99% pure. At a $1243 gold spot, there would be about $1.26 worth of gold per square inch of plated surface area. If the object is worn at all, the value would be less.
“Confusion on using correct thickness terms runs rampant on the internet. In the following seemingly official definitions for Karatclad, they use 3 different unit terms on the same page, 2 of which are in error – you would think that the person who posted this would have caught the differences. One micron equals about 40 microinches (.000040″, actually .00003937″). One mil equals 1000 microinches (.001”). I would guess that these unit errors originate in industry as inside-the-plant abbreviations of the correct terms “microinches” or “millionths of an inch”, (these 2 terms mean the same thing). Millionths is abbreviated “mils” and microinches is abbreviated “microns.” These abbreviations may work while verbally communicating inside of a plating shop but they are wrong in the real world. Another reason may lie in the huge advent of “texting”, which makes great use of abbreviations and acronyms.
“These definitions below use:
100 microinches (correct) which would be = 0.000100″
100 microns (incorrect) which would actually be = 0.004000″ – 40 times too thick
100 mils (incorrect) which is = 0.100” – 1000 times too thick.
“100 microinches is about 14 times thicker than standard gold electroplate on jewelry which has to be at least 7 microinches in order to call it “gold electroplate.”
“I didn’t realize that some of the Karatclad jewelry was marked as 18K, so, in that case, my statement concerning the purity of at least 99% would be be error. However, 18K is not necessarily 75% gold when it comes to decorative gold plating. Plated gold alloys are generally lighter in color than their cast counterparts. Therefore, to get an 18K cast color, the gold content may actually be 22-23 karat. Usually, when plated jewelry is marked 14K or 18K, that indicates the color and not necessarily the metal composition.
“18K Karatclad is equivalent in thickness to the plating on 18K HGE rings.
“Even at 100 micro” thick, which is about the thickest gold plating you’re likely to ever see (there are very few exceptions of thicker gold plating out there, whether on jewelry or electronics), the gold doesn’t contribute much to the weight. For example, if you plated a small 1/16″ dia. copper rod with 100 micro” of pure gold, the gold would only be a little over 1.3% of the total weight. If the rod were 1/4″ in dia., the gold would run about 0.34%. The “heft” of a gold plated object is definitely not a way to estimate it’s value.
“As a total guess, your pound of Karatclad would be worth between $50 – $150, depending mainly on the amount of wear, the actual karat of the plating, and the ratio of the total surface area to the total weight.”