There are a number of techniques that are effective for cleaning and preservation of artifacts. Those described here are established and have been used with great success by Digging History members or associates.
Removal of dirt, dust, and cobwebs (DDC) is best done with dish detergent and warm water. A sponge or rag may be used, depending on the material. It is not recommended that you clean silver or gold finds in the field, as you may damage the details, which can significantly reduce the collector value of those items. Softer metals require softer cleaning tools and less abrasive cleaning agents.
It is not recommended that dug items be washed in dishwashers or for removed dirt to pass down the drain in the kitchen or bathroom sinks. Debris can also damage garbage disposals and contaminate dishwasher pipes. If available, use an outdoor garden hose. If a sink must be used, a wire drain strainer should be used to catch most of the debris, which should then be discarded in the trash or outside.
Not to be confused with corrosion; corrosion occurs when the original material erodes away due to environmental conditions, leaving pitting and holes. Concretion is the buildup of material on top of the original material, usually by oxidation. Oxidation is the reaction of certain metals to oxygen in the air to form a protective but degrading layer of oxide on the outside of the metal. Iron rusts, aluminum and lead develop a white oxide patina, copper and bronze turn green, brass and silver tarnish (although silver tarnish is not caused by oxidation, it's caused by a reaction with sulfur or sulfides, the effect is essentially the same), these are all examples of oxidation that cause concretion.
There are two effective methods for removing concretion from artifacts. One is to soak it in a reactive agent. Iron is best soaked in apple cider vinegar to facilitate de-rusting. Paint, adhesives, dried & hardened food residues, and hydrocarbons (such as oil) can be removed with household solvents such as turpentine or acetone. Coins can be soaked in heated hydrogen peroxide or olive oil. Coca-Cola, lemon juice, and toothpaste all have cleansing properties and are readily available for trial and error. To remove rust stains from glass, soap and water applied with a small steel wire brush seems to be the most effective and should not cause any visible damage.
A third technique is electrolysis. This is a little more complex and potentially dangerous if not set up properly. It is a system that uses direct electrical current as a catalyst for an otherwise slow chemical reaction between an ionic salt dissolved into a solvent and rust concretion, which causes the concretion to separate from the artifact.
Grit or sand-blasting is another concretion removal method that works well for iron and steel, as these metals are durable enough to withstand the process without significant further deterioration. Of course, other metals may be grit-blasted if softer grits are used.
Tumbling coins and small glass items has seen some success as well, and is comparable to grit-blasting in terms of effectiveness. Tumbling also gives you more control over the whole process, from the coarseness or fineness of the grit to the rotation speed. Those who advocate tumbling typically use a tumbler made for polishing stones.
Once you're done cleaning and de-rusting, you don't want the artifact to start rusting again. For iron, steel, or copper non-coin items, a clear anti-rust lacquer (Rustoleum) or an anti-rust spray paint will serve you well here. For coins, following a peroxide soak, soak in olive oil for a period of time and then seal with beeswax or paraffin to prevent further degradation. Silver does not require any preservation, as removing the tarnish devalues the item, and gold does not tarnish to begin with.
It is not recommended that any dug glass, ceramic, or porcelain items be used for consumption of beverages or storage & serving of food due to any microscopic bacteria or parasites that may be present!