An iron find out of the ground is usually not an object but a lump of rust with something inside it. Sometimes there is a living core, sometimes sand and a void, and sometimes a nail you have just spent an evening on. Working out which before you start is close to impossible, and that is the central difficulty with iron.
The job comes in three steps: stabilise the metal, lift the loose oxides, and seal the surface immediately. Skip the third and two or three weeks later you are back at the first. If you have doubts about the whole exercise, start with the restoration principles.
Before any method: three questions
- Has the material actually been identified? Colour and shine prove nothing about the alloy, about plating or gilding, or about whether this is a composite object. 2. Is the original surface still there? Photographs, maker's marks, stable patina, organics, enamel, glass and thin plating can all be worth more than clean metal. 3. Is there a stop signal? Wet organics, laminated glass, plating, bimetal, loose active corrosion, an inscription, a dangerous object or a meaningful context all mean pause and a conservation route.
If even one of the three has no confident answer, do not move on to active cleaning, soaking, reagents or electrolysis. Start with the first 24 hours after a find and fill in a condition card.
Safety
Iron gets cleaned with electricity, and electricity does not forgive inattention:
- Always a current-limited supply, and never short the electrodes.
- Gloves on. Electrolyte and sludge do not go down the sink.
- Check polarity before switching on, not after. Reversed polarity can destroy a find in a single session.
Electrolysis
The full protocol — current, electrolyte, bath layout, safety — has its own walkthrough: electrolysis step by step.
What matters here is knowing when it applies at all: electrolysis makes sense on loose, active iron, and the bath must be followed by two things that are exactly the ones people skip.
Salts and iron: why activity cannot be judged by colour alone
An even orange colour tells you nothing about what is happening under the crust. Iron out of the ground is often weakened inside its own corrosion shell, and the salts left in its pores keep the process running whatever the surface looks like from outside. An object with a loose crust, cracks, possible organics or traces of plating is not automatically a "candidate for electrolysis".
The first decision here is not a bath but documentation, isolation from other finds, and an assessment of storage. If there are signs of salts, or the object has already broken down a second time, further treatment stops being a one-off procedure and moves into controlled conservation: a written plan, a conservation log and inspection dates — see monitoring after conservation.
Salts: the part everybody forgets
After electrolysis the metal looks finished, but chlorides remain in the pores. That is a deferred problem: under a coat of wax they will happily wait for moisture and restart the corrosion.
There is no single "rinse and dry" regime that fits every iron object equally. Long baths are meant for solid, uniform iron with no plating, no organics, no glued fragments and no delaminating core. For a thin-walled casting, a layered crust or a composite object, the same weeks in water are not desalination but one more cycle of damage; the mechanism is set out in water, salts and hydrolysis.
If the object clears that filter, flushing the salts out is slow and dull:
- Long soaks, or gentle boiling, in distilled water with the water changed repeatedly.
- The aim is to reduce chloride content, not to give it a rinse.
- A full dry: warmth and air, and for larger pieces more patience than you expect.
The stopping point is not a date in the calendar: change the water until a fresh change stops picking up a noticeable amount of salt. If that never happens and orange spots return after every drying, the task is no longer a rinse. It is controlled conservation, with a plan, a conservation log and scheduled inspections, and it is answered by observation and advice rather than by a longer bath.
Tannin
Tannin forms a more stable dark film on cleaned iron. It is hobby- and field-level conservation, but it works: apply to dry, clean iron per the product's instructions, then top with oil or wax.
Museum protocols are more involved, but for an everyday find the outcome is decided by two simple things — dryness and a moisture barrier.
Other options, briefly
Gentle wet mechanics will do for loose crust where electrolysis is overkill. Commercial rust converters are acceptable as a short, timed soak followed by a rinse — leave them too long and they scorch the surface. Heating to red heat, though, is best left on the internet: the crack risk is high, and for thin or hollow castings it is close to a guaranteed ending.
Background in chemistry and tools, storage in preservation.
Consolidation is not optional
- Dry iron, then a thin film of oil or a suitable wax.
- Dry storage; silica gel in the box does no harm.
- Periodic inspection. Fresh orange spots mean drying and sealing again, not "a bit more acid".
What to record
Photograph the corrosion layers before the bath and pin the spot on the map. With iron the context is usually worth more than a tidy strip: a nail on its own says nothing, while a nail on the footprint of a former building says quite a lot. AI restoration in the app is useful for documenting the shape while the original is still in its crust.
In short
- Polarity and electrode isolation checked.
- Electrolysis only once the stop signals have been checked; then a rinse.
- Distilled water and desalination — do not skip, but match the regime to the object.
- Dry, then tannin, oil or wax.
- Dry storage and the occasional look.
External orientation
Iron is more demanding about storage than any other metal here. For stabilisation and microclimate see the metals section at Canadian Conservation Institute; home electrolysis is not a substitute for lab conservation.