After discovering that the vase was badly cracked all the way up from the bottom, we were on the way out when I spotted this lonely old pestle&mortar set standing among much shinier but less interesting items.
I picked it up and noted how nicely it fitted into the hand. Apart from the rust it had crude but never the less lovely cast iron details. Holding it I remembered all of a sudden that my grandparents had a very similar one, and let me play with it in the sand pit sometimes when I was a kid.
As usual, it didn't take me long to take a shine to an old unloved item that had some meaning for me, especially when it went for very cheap. I also thought to myself that I'll make this into a little restoration project. After spending a couple of hours on it once back at home, this is what I ended up with:
To be honest, more often than not I like preserving old items in their patina-ed original condition, as I believe it adds to their appeal. However, when it comes to this much rust on such a beautiful object, I prefer to get rid of all that corroded patina to put a stop to the iron being slowly eaten by it. I'm almost certain that the old cast iron is thankful for the treatment and will even develop a new, more healthy patina with time as long as we look after it properly. That means no washing with water at all, and a rub-through with vegetable oil every now and again.
The way I restored my cast iron pestle&mortar involved a throw-away fine emery fingernail file with a raspier and a smoother side, a whole sheet of superfine sandpaper, some almond oil, paper towels, a piece of cloth and a face mask to filter the air while filing and sanding.
The nail file helped to get off the rust, the bits of chipped paint and the caked on patina. The superfine sandpaper was used to gently clear up large surface areas including the inside of the cup, and to reveal more of the shiny cast iron. The almond oil fed and helped to clean the iron - I applied it generously then wiped over and over using paper towels. Once the wiped off oil showed up clean on the paper towel, I gave both pestle and mortar a buff with a piece of cloth to soak up any excess oil and that was it.
Please note, this method of restoration is only good for cast iron, and not suitable for other types of metal. If you need to restore cast iron cooking pots or pans, the method is a bit different - it involves an overall more careful treatment and baking the item.