Sterling Silver Tarnishing and Discolouration  Gold
Sterling silver is a metal containing at least 92.5% silver. This is the legal standard of purity set by the assay offices in Britain and used for all of our silver jewellery. Pure silver is never used, as it is too soft to be practical and ‘925 Sterling Silver’ is the industry standard and very high quality. All are pieces are assayed and Hallmarked in London by the Goldsmiths company.

With time, any sterling silver jewellery piece that is exposed to air will tarnish. Sterling silver is a mixture of metals with at least 92.5% silver and 7.5% other metals.
And it is the other metals, usually copper, that oxidised in the air resulting in the build-up of a tarnished layer on sterling silver jewellery.
Silver tarnishes faster in areas with high humidity and air pollution. Additionally, contact with materials like cosmetics, hairspray, perfume, deodorant, body lotion, bleach, etc, can speed up the tarnishing process. The silver in your ring may also become oxidised by reacting with natural sulphur from a variety of sources such as acids in your skin, fruit, the moisture in perspiration, or by reacting with some other lotion or chemical on your skin.
Make-up present on the skin or clothing is the most common cause of blackening or smudging. Cosmetics often contain chemical compounds which are harder than the jewellery itself. These compounds can rub off very tiny particles of metal which appear as jet black dust.
A solution is to use a silver cloth to polish your jewellery, We recommend 'Hagerty' or 'Goddard's' cloths available from jewellery suppliers or on Amazon at a relatively low cost. Remember to remove rings and jewellery while applying make-up. Using soap and water, clean the areas of your skin that will come into contact with the jewellery making sure all soap is rinsed off and your hands are dry.
Over time with daily wear and exposure to the elements gold will dull and lose its initial shine. If the gold jewellery has gemstones, please be extra careful when cleaning the piece and avoid applying excessive pressure. A cleaning solution designed exclusively for jewellery is a safe option, but make sure any solution is specific to the correct metal. If you’re unsure you can easily us the following method in most cases.
Add some drops of washing-up liquid (or other mild degreasing solution) to a lukewarm bowl of water. Extreme temperatures aren’t good for the jewellery, so avoid very hot or ice-cold water. Soak the jewellery for ten minutes to loosen any build-up of dirt. Gently clean with a soft-bristled brush such as an unused toothbrush. Make sure to clean the whole piece of jewellery and get into hard to reach places but work delicately around stone settings etc. Rinse thoroughly in clean water to remove soap residue and any other remnants of dirt. 
You can also purchase an impregnated Gold Polishing Cloth to maintain a daily shine. These are very effective and last for a long time. We recommend ‘Hagerty Gold Cloths’ which are available from many independent jewellery suppliers or on Amazon at a relatively low cost. 
Gold is a very soft metal that is susceptible to scratching. Remember this fact during the cleaning and drying process and be as gentle as possible.