Thursday, 29 September 2011

Argentium in Evening Standard Newspaper

The Evening Standard Newspaper kindly mentioned Argentium Silver in their 'Design trends - silver' article published on 28-Sep-11... describing Argentium as "the new magic stuff used by many new makers to take the chore out of cleaning".

The article promoted the beauty of silver and advertised the forthcoming Goldsmiths' Fair in London.  Click here for for a list of exhibitors and opening times for the fair...

Tuesday, 20 September 2011

Is Argentium sterling quality?

We are often asked whether Argentium Silver can be hallmarked as sterling quality (identified by the 925 hallmark).  The answer is 'yes'.

To explain further, there are two grades of Argentium Silver...
  • Argentium 935 (93.5% silver purity)
  • Argentium 960 (96.0% silver purity)
As both of these alloys each contain a greater silver purity than the required 92.5%, they easily surpass the sterling quality standard.

Argentium 960 also surpasses the British Britannia standard set at 95.8% silver purity. 

Tuesday, 6 September 2011

Rio Grande's 'The Studio' Blog

On Rio Grande's 'The Studio' Blog you can find some wonderful resources.

Recent postings have included book excerpts by Scott David Plumblee - showing you step by step tutorials how to make pretty beaded earrings and headpins.   Take a look!...

Printable instructions from Scott David Plumlee's posts can also be downloaded from the blog.  

Monday, 5 September 2011

How Silver is Silver?

This is not a question about purity; rather it is a question about colour.

How do you assess the degree of polish or lustre on a silver item? What is the different in colour between an item which has been silver or rhodium plated and the polished silver alloy? Is there a difference in colour between different silver alloys?

All of these questions go through our minds when we examine a finished piece for quality or consider the merits of a different silver alloy for our work. Many of us ‘shade’ a finished item with a piece of paper to assess its surface finish and so reduce the effects of reflected light which might mask surface defects. However, it is the use of reflected light which forms the basis of colour measurement systems.

In its simplest form you take a light of known intensity, shine it on a surface and measure how much light is reflected back to you. This measurement of ‘reflectivity’ gives a simple measure of the brightness and whiteness of the object being tested. To standardise the test you can specify the power of the light source and the angle at which it is shone at the object under test, but how can this principle be used for test for colour?

White light can be split into different coloured components. (This gives me an excuse to include the iconic Pink Floyd Dark Side of the Moon album cover which shows white light being split into separate coloured components by a prism!)

So to measure colour we need only to do the same thing in reverse; shine a white light at an object and measure what coloured components are reflected back, rather than the overall amount of white light.

This is the principal behind the Yellowness Index, the colour measurement system used to determine for white golds which are white enough not to require rhodium plating. (For those interested the Yellowness Index is based on ASTM standard D1925, but I do not intend to go into its details in this post.)

In fact white golds are split into three categories dependent on their colour; premium white grade, these alloys have a good white colour and do not need rhodium plating; standard grade, rhodium plating is optional for these alloys and off-white, these alloys need to be rhodium plated. Any alloys falling outside of these three grades are classed as non-white.

To take this principal of colour measurement further, if we can quantify what colour silver is then we can also use colour measurement as a way of measuring tarnish (or to put it another way, colour change with time). There is an established technique called the CIELab system which is widely used for measuring colour using a colour photo-spectrometer (simply a device which can detect the different wavelengths of light reflected into it and measure the intensity of each wavelength).

The diagram opposite shows how this system can use three values, or co-ordinates, to describe in a quantitative way any colour.

The L* co-ordinate measures the degree of brightness or lightness from 0 which is black to 100 which is white. This is also a measure of the reflectivity of the item. The a* co-ordinate measures the red-green component of colour and the b* co-ordinate measures the yellow-blue colour component.

So in this system a perfect pure white would have L* =100 and a and b =0 and also any colour can be described by these three values, L*, a* and b*.

In another blog posting I will describe how this colour measurement system can be used to quantify the degree of tarnish present on a silver alloy after testing but I hope this explains how we can assess the different colours of white metals and explains how we can measure what colour silver is.

Thursday, 1 September 2011

Featured Argentium Guild Members Sept 11

This month's featured Argentium Guild Members are Jenny Reeves and Diana Kirkpatrick (Corner Studio Jewelers) and Bridgette Rallo (The Greenwoods Studio).  See more of their jewellery designs by clicking on the following link...​featured-members