How to Clean and Preserve Finds
The moment an object is pulled from the ground, its environment radically changes. Artifacts that have spent centuries in stable, anoxic soil conditions are suddenly exposed to oxygen and fluctuating moisture levels, which can rapidly accelerate degradation. Proper cleaning and preservation techniques are critical. The golden rule of artifact conservation is simple: do as little as necessary. Aggressive cleaning destroys patina, damages surface details, and obliterates historical value.
Assessing the Artifact
Before any cleaning begins, you must accurately identify the base material. The approach for a gold coin is entirely different from the approach for an iron horseshoe. Gold is inert and generally requires no more than a gentle rinse. Silver can tarnish but usually survives well. Copper alloys (bronze, brass) develop a protective patina that must not be stripped. Iron is highly unstable and prone to rapid oxidation (rusting) once exposed to air.
Mechanical Cleaning
For most non-ferrous finds (copper, bronze, silver), mechanical cleaning is the safest starting point. This involves physically removing dirt without using harsh chemicals.
- Dry Brushing: Let the artifact dry completely. Use a soft-bristled brush, such as a toothbrush or a specialized conservation brush, to gently sweep away loose soil. Do not use wire brushes on non-ferrous metals, as they will deeply scratch the surface.
- Distilled Water Soak: If dirt is encrusted, soak the item in distilled water. Tap water contains minerals and chlorine that can react with ancient metals. A prolonged soak in distilled water will safely soften hardened mud, which can then be gently picked away with a wooden toothpick or a soft brush.
Chemical Cleaning and Electrolysis
Chemical intervention should be a last resort and is generally only recommended for severely encrusted items or specific materials where mechanical cleaning is ineffective.
For silver artifacts covered in a hard, black silver sulfide crust (horn silver), a brief soak in a weak acidic solution like lemon juice or specialized silver dip can be used, but the item must be monitored continuously to prevent pitting. The acid must be thoroughly neutralized in distilled water immediately afterward.
Iron objects present the greatest challenge. Thick layers of rust cannot be brushed away. For stable iron relics, electrolysis is a standard conservation method. This involves passing a low-voltage electrical current through a conductive solution (usually water mixed with washing soda) to reverse the oxidation process, converting red rust back into a stable black oxide and loosening concretions. Electrolysis requires specific safety protocols, as it generates hydrogen gas.
Preservation and Storage
Once an item is clean and completely dry, it must be sealed to prevent oxygen and moisture from interacting with the metal.
For copper alloys, microcrystalline wax (such as Renaissance Wax) is the industry standard. Applied sparingly with a soft cloth and buffed, it provides a highly stable, reversible moisture barrier that deepens the visual contrast of the patina without making it overly glossy.
Storage is the final step. Artifacts should be kept in a stable environment with low humidity. Acid-free archival boxes, padded with inert foam, are ideal. For coins, PVC-free flips or capsules are necessary, as the plasticizers in cheap PVC will slowly leech out and chemically damage the surface of the metal, creating a sticky green residue known as "bronze disease." By treating every find with caution and respect, you ensure that these tangible pieces of history remain intact for future generations.