Most silver plated cutlery and hollow ware is marked 'E.P.N.S.' - the abbreviation for 'Electro-Plated Nickel-Silver'. 'Nickel-Silver' identifies the base metal as a copper-zinc-nickel alloy; it contains no silver but, because its nickel content imparts a colour more akin to silver than brass, it has always been known as 'nickel-silver'. 'Electro-plated' in this context means that the articles are electro-plated with silver - the first metal to be used extensively in electro-plating. In many countries including USA, nickel silver is not used, but brass is used instead.
Stainless steel cutlery or hollowware is sometimes silver plated, in which case it may be marked 'E.P.S.S.'. Knife blades with a cutting edge are made from stainless and are not plated with silver because it would blunt their edges. The life of silver plate depends upon its thickness and how often it is used. A household that saves its silver plated cutlery for special occasions may use it on average only once a month - elsewhere it may be used several times a day. When selecting cutlery, it is advisable to compare the thickness of silver claimed to be present on each and every piece (averages based upon half a dozen pieces are less meaningful because some pieces are likely to have a significantly thinner silver thickness than that average). Silver thickness is normally quoted in 'microns'. (One micron is one thousandth of a millimeter). As a very approximate guide, work on at least 1 micron of silver thickness for every year of intended use.
The characteristic white 'patina' of silver which is responsible for much of its aesthetic appeal becomes more pronounced with age due to the optical effect of the multitude of very fine scratches that develop in use. On new highly polished silver, however, the few fine isolated scratches that first appear tend to be somewhat conspicuous until the white patina has fully developed.
Silver, being a noble metal, is highly resistant to corrosion, but it can be tarnished by sulphides that are always present to some extent in the atmosphere and in many foods, green vegetables and eggs being the most potent. Tarnish consists of a superficial film of silver sulphides. Initially it is a light gold colour, but, with prolonged exposure to sulphides, it can develop into a blue-black discolouration.
Sulphides in the atmosphere originate mainly from combustion of gas oil, coke, wood etc. and from living creatures. To avoid the need for frequent cleaning, it is best to store silver cutlery in a box or drawer in a room without a fire of any type and, if convenient, in one of the lesser used rooms. To avoid tarnishing by food, rinse it off the cutlery as soon as convenient. Tarnish resisting papers and cloths are available to store silver, which certainly reduce the rate of tarnishing.
Four methods of detarnishing silver are available: polishing powders or pastes, chemical dip solutions, electrolytic methods and ball burnishing.
Only those sold specifically for silver should be used; cleaners intended for chromium plate, stainless steel etc will scratch silver. Always apply the cleaner with a soft cloth or sponge - either of which should be thoroughly and freshly washed to eliminate any abrasive dust particles which could cause scratching.
Some cleaners that are available in paste or emulsion form, not only remove tarnish but contain tarnish inhibitors. Such products are particularly useful for hollowware (being handled, washed and wiped less frequently than cutlery, the inhibiting effect lasts longer).
Over zealous pressure when cleaning with powders may remove significant amounts of silver which ultimately will wear through the plate completely.
Provide a rapid, less arduous method of detarnishing, especially on heavily embossed designs whose crevices are difficult to clean with silver powders. These dip solutions convert the film of tarnish (silver sulphides) back to silver by removing the sulphides without removing any silver. However, the following precautions must be taken:
- (1) Never leave silver plated cutlery in the dip solution for more than 10 seconds.
- (2) Do not use dip solutions to remove very heavy tarnish. They will convert the silver sulphides to silver but, because heavy tarnish is thicker, the surface of the restored silver may have a matt finish.
- (3) Dip solutions can stain or even etch stainless steel knife blades. Any drops that fall onto blades or other stainless steel equipment should be rinsed off immediately.
Tarnish can be removed from silver by immersing it in a hot solution of washing soda of about 30 grams per 5 litres whilst the cutlery or hollowware is in contact with aluminium.
Proprietary kits are available but the process can be carried out on a DIY basis in a plastic bowl with a sheet of aluminium foil laid in the bottom so that the cutlery is in contact with the foil. When the foil eventually darkens and becomes brittle, it becomes ineffective and needs replacing.
As in the case of chemical dip solutions, the process is not suitable for use on very heavily tarnished silver upon which it can produce a dull white finish.
This is a bulk process for use in large catering establishments. The cutlery is placed in a rotating drum containing steel ball bearings, water and a corrosion inhibitor to prevent the steel balls from rusting. Its prime purpose is to brighten and harden the surface so that it becomes more resistant to scratching and wear. However, it will also remove light to moderate tarnish, except in the crevices of heavily patterned pieces.
Despite the apparent severity of the process, it does not wear off the silver if carried out under intelligent supervision and in accordance with the machine supplier's instructions. Problems likely to occur are:
Entanglement of fork prongs which may cause some to bend. This can be avoided by positioning the compartment separators closer together so that the forks stay orientated across the barrel.
A matt scratched finish, caused by having insufficient water in the burnisher - this can occur as a result of leakage if the machine's lid has not been adequately tightened or if its seal is defective.
Developments of grooves on the sides of vessels such as tea post. This is caused by the compartment separators being too close together, thus allowing steel balls to become entrapped between the separators and the sides of the vessel - to the detriment of the latter. Compartment widths should be adjusted to suit the width of vessel being burnished.
Hollowware can be damaged if large heavy items are burnished in the same compartment.
First, it must be emphasised that staining is a rare phenomenon and that in most cases it is due to something that becomes firmly deposited on the steel, rather than to any attack of the steel itself. Probably the most common cause of staining is attack by one of the proprietary dip solutions used for removing tarnish from silver. Although excellent for cleaning silver and E.P.N.S., these solutions should never be allowed to come into contact with stainless steel; they contain acids that etch the steel, first giving it an iridescent rainbow stain and ultimately etching it a dull grey. Even if care is taken to dip only the silver handle of a knife, it is so easy, when lifting it from the solution, to let drips fall onto the stainless steel blades of other cutlery that happen to be lying around.
All tap water contains dissolved mineral salts that would leave an extremely thin film on any article on which it was allowed to dry out without wiping. In most cases, the resultant stain will wipe off, but occasionally more vigorous treatment is needed, using a polishing preparation, such as stainless steel cleaners.
Detergents, especially unnecessarily strong solutions of detergent, can leave an indelible rainbow stain on stainless steel if they are not rinsed off and are allowed to dry, out on its surface. This is a common problem with some dishwashing machines when the rinse cycle is malfunctioning.
Very hard water can deposit a chalky film on stainless steel, but this is only likely to occur in dishwashers that use un-softened or incompletely softened water.
Very hot grease, fat or meat juices sometimes leave stubborn rainbow coloured stains on stainless steel, but this is more likely to occur on meat dishes than cutlery - again this does not mean there is anything wrong this the stainless steel and the articles will be as good as new after the stain has been removed.
Heat by itself will impart a rainbow coloured heat tint to stainless steel, but this is only likely to occur if the cutlery is accidentally left on a hot plate or gas burner, when the cause would be immediately obvious.
Prolonged immersion in synthetic 'vinegar' (condiment) can stain stainless steel knives if left on for several hours, but more rapidly if the 'vinegar' also contains salt.
Sometimes rust coloured stains occur. Wet fragments of steel wool that find their way onto cutlery may go rusty and leave indelible rust stains on the stainless steel. Other rust coloured stains may come from corrosion pits in the cutlery, although the pits themselves may be so small as to be barely visible.
Most stains that resist ordinary rubbing with a soapy cloth can be removed with stainless steel cleaners.
Finally, it must be pointed out that there may be other causes of staining that have not yet been identified.
When stainless steel corrodes, it does not rust all over like non stainless steel but acquires small localised pits or holes. Remember its STAIN LESS steel which means it will rust or corroded under some circumstances.
The majority of spoons and forks are made from stainless steels that have such excellent corrosion resistance that they are virtually immune to pitting. For knives, however, the blade steel is selected to give a compromise between corrosion resistance and cutting properties. In order to achieve a lasting edge, a steel that is much harder but of lower corrosion resistance that spoon and fork steel is used. The corrosion resistance of this steel is strongly influenced by care in manufacture (thorough hardening and avoidance of overheating when grinding etc) but only marginal improvements are achieved by the selection of alternative steels, however, expensive. Research is continually being carried out in the search for significantly better steels and method of treatment.
Prolonged contact with water is probably responsible for more pitting trouble than anything else. Knives have been made from stainless steel for such a long time that the highly corrosive effect of tap water, caused by the traces of mineral salts it contains is not appreciated. Why then do blades in one establishment last for years without trouble, whilst in others pitting becomes apparent within a few months? The answer lies in the length of time the blades are wet; knives that are left undried or actually immersed in water overnight can receive, in this time, as much exposure to the corrosive effect of water as three or four months' ordinary use where they are in contact with water for only a few minutes each time they are washed.
Common salt and liquid bleaches or disinfectants are very corrosive and will greatly accelerate the corrosive action of water. Some water softeners are regenerated with salt. If they are not functioning correctly, the softened water can have a high salt content. After adding salt to water softeners in a dishwasher, make certain that it is put through the rinse programme recommended by the supplier before washing knives in the machine. Detergents, on the other hand, are normally harmless when fully dissolved - indeed they often inhibit corrosion by water. If, however, certain powder detergents are allowed to come into contact with blades in hot water before the detergent is fully dissolved, pits and/or stains can form within a few minutes. Un-dissolved table salt can have a similar effect.
If pitting does occur, a diligent enquiry into the washing procedure is recommended to find out whether the cutlery is ever left in contact with water for a long item. Managers of catering establishments are not always aware of what really happens in their kitchens - for example, probably only the person directly involved may know that dirty cutlery is always left soaking in a bucket of water until someone has time to wash it, or that the last batch of knives to be washed in the early hours is left unwiped to dry overnight in a humid basement.
Dishwashing machines provide a welcome relief from the task of washing up but to maintain knives in good condition a few simple precautions are necessary. Special hardenable stainless steels are generally used for knives to give them a lasting edge but these steels can become slightly pitted or corroded if left repeatedly and for too long in contact with moisture.
Printed copies of this document are available to cutlery manufacturers, distributors and retailers for inclusion with cutlery/flatware at the point of sale.
This information is given without liability in connection with its application or use in particular circumstances
CATRA can provide specific help for users where they are experiencing problems
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