Wednesday, December 21, 2011

Gold-plated, gold-filled... what does it matter?

Being engaged in jewelry art for many years, and working with many different people, I have noticed that many customers – and even master jewelry makers – don’t always understand or appreciate the difference between metal covered with gold-plate (also called gilding) as opposed to the gold-fill process (sometimes called cladding, overlay or gold-rolled).

Both involve a base metal (brass, copper, or silver) fused with a top layer of gold, so the surface appearance is the same. But the difference becomes important for other reasons, as I personally discovered with my husband’s cuff links. More about that later...

There are two basic distinctions between gold-plate and gold-fill:

[chart – gold electro-plated]

(1) The thickness of the gold layer for gold-plated metal is 0.5-8 microns; for gold-filled metal it’s 5-120 microns (1000 microns = 1 millimeter).

Obviously, gold-fill has a much thicker layer of gold, which directly affects the price of the piece. In the two tables below, we see for example that a gold-filled bracelet has at least 10 times more gold (30-120 microns) than a gold-plated bracelet (2.5-8 microns). This is why gold-plated pieces are so much more affordable.


[chart – gold filled]



But you also want your jewelry piece to keep its gold look for a long time – especially if it becomes a favorite that you wear often! Notice the difference in the “life expectancy” of the gold-plated compared with gold-filled jewelry pieces in these two tables.

Add to this the fact that in practice, the thickness of a gold layer in gold-plate is often much less than what you see in this table, which makes the metal correspondingly less durable... So is the bargain price really a bargain?
(2) In gold-filled metal there is an intermediate layer of gold alloy between the gold and the basic metal (which is why it’s called “gold-filled”). This layer is missing in gold-plated metal.



[chart – cross-section of gold-filled]

The intermediate layer plays a key role in the durability of the gold look. Gold tends to “diffuse” or mix in with the atoms of other metals. In gold-plate this intermingling happens rather easily, allowing the base metal to rise to the surface and causing the gold look to fade. The intermediate layer in gold-fill, made of a blend of gold and brass, captures and holds atoms in the top gold layer and the bottom brass layer.

This interlocking action makes the gold diffusion process slow and gradual, together with there being more gold to start with! In the long run, the beauty of gold-filled jewelry lasts many years longer, making its higher price more worthwhile.

The lesson of my husband’s cuff links.

When we still lived in Vilnius (Lithuania), I bought my man a set of beautiful cuff links as a gift. They were made from gold-plated silver and inset with rock crystal. He thanked me, put the cuff links back in their box... and never touched them again. Oh, well.

Some years later, already in Israel, I was sorting through things and come across this box. I opened it, and was very surprised to see pure-white cuff links inset with rock crystal. The gold layer had completely disappeared, even though the cuff links had never been worn even once.

So diffusion is unstoppable, no matter how carefully you clean and store your gold-plated jewelry. If you love the color of gold, invest your hard-earned money in gold-filled pieces to avoid disappointment.
http://en.wikipedia.org/wiki/Gold-filled_jewelry
http://www.artisanplating.com/articles/goldfilled.html#comparison

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