Note 5: Take Advice Before Cleaning

Show your finds to your nearest FLO, who will help identify them and advise you on good practice. Once you are certain the find is not Treasure you can decide what to do next. A professional conservator might not charge as much as you think. You can find an accredited private conservator through the Conservation Register or through your local museum.

Some of your finds will be collectibles, such as livery buttons, pilgrim badges, hammered coins and tokens; others may be agricultural in origin, like horseshoes and harness fittings. As a rule of thumb, the older the item, the more heavily corroded it will be, and many ancient objects made from copper alloy will have developed a patina which adds value and beauty to the object.

Removing this patina could seriously damage and devalue the object and lose information. But many of your finds will be fairly modern, like milled coinage, watch-fobs, penknives and other casual losses. These more recent items can mostly be cleaned carefully without them coming to harm but there are no quick fixes'!

A conservator cleaning an object under a microscopeCleaning by hand is the best way to remove thick corrosion layers, working with fine hand-tools and with the aid of a low-power microscope. Use sharpened wooden or plastic points such as cocktail sticks and artist's brushes to remove loosened soil. Practice first with scrap objects until you get experienced at it, as much skill and practice is needed to produce good results. Don't use barrelling, wire brushes or other harsh methods they will only cause damage. Remember, the purpose of cleaning an object is to reveal the original surface detail. This surface may be within the layers of corrosion and no longer be metallic.  Many metal corrosion products are poisonous, so wear a dust-mask and disposable gloves, especially when cleaning lead alloys. Chemical cleaning should only be used to remove tarnish from more modern objects where the original surface is well-preserved. The image on the right shows the damage caused to a silver short-cross penny through over-cleaning with Sodium Hydroxide.

Example products that should not be usedAlways remember that chemicals can be dangerous to you and your finds and great care should be taken in their storage and use at home. Chemical reactions cannot easily be controlled and some chemicals may remain in the object and cause problems later. Even lemon juice and vinegar are chemicals and can cause damage to metal surfaces. Use only materials designed for the job.

If you must remove tarnish from silver, polish brass items, and remove the rust from your ironwork, then there are lots of proprietary products available at hardware stores. But be warned: none of these products are conservation-grade materials, and you use them at your own risk. When undertaking chemical cleaning: Watch out for additional materials, such as inlays or plating, they can be fragile. Watch out for attached organic remains': Don't let the chemical product come into contact with bone, leather, wood, textiles etc. Wash off any chemical cleaning agent from your object very thoroughly after use.

Joining: For objects in fragments that need joining, it is important to find the right adhesive for the particular material. Adhesives used with artefacts should ideally be reversible, so you can easily undo the join using a solvent if you make a mistake. For corroded metals, use a recommended reversible adhesive, such as Paraloid B72' or cellulose nitrate' from a specialist supplier. Never use super-glues as they can be chemically unstable, and are difficult to apply and control. If a stronger joint is required for a large or heavy object, you may have to resort to an epoxy adhesive, such as Araldite ® . If you do use an epoxy, make sure it is of good quality and the right sort for joining metals. But remember: you may never be able to undo it again!

Never solder or weld objects; any process involving heat will change the metal's structure and obscure detail. Coatings are commonly used both to protect and enhance the surfaces of objects. But a surface coating is seldom really necessary for protection if you are handling your finds correctly and storing them in a dry box'. If you must apply a coating to your finds:

  • Don't use domestic waxes, oils, petroleum jelly or shoe-polish they all contain potentially harmful contaminants
  • For bright metal surfaces, use an appropriate lacquer, such as Incralac'
  • For corroded metals, coatings can be used to consolidate a fragile surface. Use a conservation-grade resin solution, such as Paraloid B72'
  • Make sure you read instructions carefully, especially health and safety advice, before using any specialist materials.

Restoring: This is the process of filling holes and gaps or making up spare parts for an object which are missing. If carried out in such a way that the restoration is invisible, it amounts to faking, which is both misleading and dishonest. If an object is damaged, then this is part of its history. It is better to leave it alone and let it tell its story without intervention!

Conservation for Metal Detectorists' will give you further advice on both mechanical cleaning techniques and on the use of specialist chemical cleaning reagents and surface lacquers, along with a list of suppliers, health and safety and other important information.