Silver Tarnish - What Causes It?

Silver tarnish is a normal process that causes the surface of silver items to darken through exposure to air and skin. According to silver cleaner producer Goddard's, tarnish is caused particularly by air making contact with moisture on the surface of the metal. This explains why tarnish can be a problem when silver dog tags are worn next to skin in hot weather: there's plenty of sweat which contains, amongst other chemicals, salt. All silver items sold by 10STERLING come from highly reputable manufacturers either in the UK or, for our ball chains, the USA. All items weighing more than 7.78g (in practice that’s all items except very small crosses or earrings) are tested at the London Assay Office for silver content which by law can be no less than 92.5% pure silver if it's sold as "sterling silver". 
This testing process is done using high precision laboratory equipment (including Non-Destructive X-Ray Fluorescence) and is something 10STERLING pays for in order to comply with the UK Hallmarking Act 1973. Once tested, each item is physically stamped (hallmarked) by the London Assay Office. The Assay Office will refuse to hallmark any silver item if it's not at least 92.5% pure and there's no tolerance for error in this test. They have the legal right to destroy, before returning to the maker, any item submitted for hallmarking that doesn't meet the purity requirements.
The other 7.5% of the metal in sterling silver is made from other metals, including copper, to give stength. It's vital to add stronger metals to impart stiffness to silver because jewellery or items made from 100% pure silver can't resist bending and general wear. In it’s completely pure form, silver has something like the strength of lead, i.e. almost none. This is how silver has been made for thousands of years and a check on Wikipedia or, more authoritatively, the website of the Goldsmiths Company, which also incorporates the London Assay Office will confirm this.
There is, however, a downside to adding other metals (except germanium, found in Argentium silver) because it increases the speed and extent of tarnishing. This is totally natural, however, and every piece of silver jewellery in the world will, sooner or later, go dull with tarnish unless it's kept in an airtight, moisture free container. The good thing about silver tarnish is that it's very easy to remove. 
Information on caring for our silver products is available on the Product Care page but we've reproduced it here. 
1. Regularly clean your sterling silver item by first removing the metal chain or cord if it's not silver: if it's silver then just leave it attached. Then wash it by rubbing it with your fingers, or a soft cloth, in a solution of mild liquid soap and water. Liquid hand soap or washing-up liquid is perfect for this. This will remove the oils and grime that come from wearing it next to your skin.
2. Rinse it thoroughly and dry. This is important because some liquid soaps (e.g. washing up liquid) contain salt which will mark silver. Then polish using a special impregnated silver cleaning cloth like the one below which are sold on this site here Care & Service. Many other equally effective silver polishing cloth brands are sold in High St jewellers and some hardware stores including those made by Hagerty and Goddard's.
Be sure to polish from one end of the tag to the other, backwards and forwards, in the same direction: don't change direction or polish in circles because this will reduce the level of shine that can be obtained. Change the part of the cloth in contact with the silver quite often. When the cloth goes black then it's still OK to use - don't throw it away. To polish a chain, fold over a piece of the cloth and gently but firmly pull the chain through from one end to the other several times.
It’s easier, and keeps your silver dog tag looking shinier longer if this is done regularly. Never wash your silver polishing cloth or the impregnated cleaning compounds will be removed and it will cease to be effective.

If the silver dog tag isn't worn for an extended period, or it it's worn in very hot weather when the wearer is sweating heavily, then it'll become very dull or discoloured quite quickly. In this case you need to use a silver dip such as Goddard’s Silver Dip or Hagerty Silver Clean. These products are widely available from High Street jewellers or from online shops. Liquid dips do what they claim to and work quickly to remove tarnish from all areas of the silver surface, including recessed areas. It should, however, be used sparingly and only when the item is badly tarnished because it's quite an aggressive cleaning solution. Examples of two silver dip products are shown here:
3. Completely immerse the tag and chain (do NOT put cords or chains made from either leatherstainless steel or titanium into silver dip because this solution may damage these materials) and agitate the chain and tag with a plastic needle, plastic fork or wooden kebab stick or similar for maximum cleaning effect.
4. After 1 minute, or less, remove the silver items and rinse thoroughly in clean water then dry. Silver dip solutions work very quickly.
5. Finally, buff to a bright shine with an impregnated silver cloth.
Bathing: showering or bathing in fresh water won't cause tarnish to develop more quickly - it makes no difference. But swimming in either chlorinated pools or the sea (which is salty) will speed up tarnishing. This can be removed by following the cleaning instructions above but it may require more elbow polishing grease!
If you search for 'silver tarnishing' on the internet you'll get all the information contained above. Rest assured, silver tarnish is just one of those things. In fact, if a silver item doesn't tarnish then it may not be made from real silver.