Citric soak

[GIO]

Originally Posted by drdavid

Hi Gio
what strength NaOH have you used in this set up
what sort of wire are you using in the coils, copper?
regards
DrDavid

Hi David
Please apologize for my late answer, but a thunderstorm has put out of order my phone line and burnt my modem. Only this morning all has been repaired,
As to the electric de-rusting, my plant is not exactly what recommended in the book, but it works.
I use a rectangular plastic flower pot, on the floor of which I have put a serpentine of iron wire (about 1,5 mm thick). The quantity of NaOH is 1 - 2 tea cups per 5 litres (I think that the concentration has some influence on the time required for cleaning). The rheostat is needed for starting the reaction with a low voltage, increasing it slowly. I do not have a rheostat and I use a car light bulb to avoid a short circuit. The power comes from a 12 V car battery charger. Obviously the piece to be treated should not touch neither the iron wire. I suspend it with some pieces of plastic.
When the reaction starts, I can eliminate the bulb, and the reaction becomes more violent, but I prefer to leave the bulb in the circuit to avoid any risk, particularly when the system is unattended. Of course the current is lower and time needed is higher.
When the process ends the piece is black and it needs to be brushed to eliminate all the transformed rust.
When I am back home (beginning September) I shall send you the original text (from a French book: "Restauration des armes à feu"). If you have any doubts please feel free to contact me again.

Alan
Yes, I agree with you: any de-rusting treatment is very risky to kinatah if the iron is heavily rusted. If the rust is light and has not yet developed under the gold foil the treatment is safe, but always great attention is needed.

[A. G. Maisey]

Thanks for your additional comment Giovanni.

Where the kinatah work is only gold foil I would be reluctant to touch it with just about anything, even when it looks good and not heavily rusted, but there is also much heavier kinatah work that uses either very heavy gold over an iron carved figure, or heavy carved gold. With this type of work I believe your electric method could be fairly safe with any except the worst of corrosion.