My Mom recently gave me an antique brass mortar & pestle that had belonged to my paternal grandmother. I’ve d polished it up & it looks great, except for some corrosion inside it. I have no idea how to remove it. Here are some pics; Any suggestions would be welcome.
Try a No. 2 pencil. The lead is abrasive enough to scrape off the corrosion, but soft enough that it won't mar the bowl. No promises, but I've taken rust off my knife blades that way.
You could try brasso which will remove tarnish really well but it looks like there may be some pitting there. If there is, you'd probably have to use some something like sandpaper to remove some material and get back to a nice smooth finish. I'd start as fine as possible, like around 1000 grit wet-or-dry (use it wet) and go courser if it's not working fast enough for you. Then go finer and finer until you get a good shiny surface. If you use brasso or any other chemicals, you'll need to clean it out really well before using it obviously.
If it’s solid brass then you can remove the corrosion as previously described. I’ve used fine steel wool with Brasso as well as fine wet/dry sandpaper. If it’s brass plated there’s not much you can do.
If that's the inside, it's probably something stuck on from using it and a fresh green scrubby and a wooden spoon should take it off.
One thing I just thought about. Brass sometimes has some lead in it. You might want to use a home lead test kit to check that before using it for anything you're going to eat, and before taking any sandpaper to it. If it does turn out to have lead in it, it's still a nice decoration.
@feeltheburn as it is quite old, it has occurred to me that it might have lead in it. I have no intention of using it for food. This will be lacquered & displayed.
The proper way to clean up the corrosion would be to use a do-more or die grinder with a wire wheel on it. They make the wheels and cups out of various things, starting with nylon, brass, and working up to stiff wire. The home use equivalent would be a dremel. As for lead. Removing surface lead from brass/bronze is easy. It's as easy as soaking in a mix of white vinegar and hydrogen peroxide for a short time. Detailed instructions can be found online. This is a common problem in the brewing industry, and the corrective measures were developed by NASA. Once this process has been done, your mortar and pestle can be returned to the food service use it was made for.
Acids are a common way to remove rust/corrosion - more specifically a paste of vinegar and salt for cleaning copper and brass ( which is a copper and zinc alloy). Did you already try that? Plenty of diy tutorials on yt how to do it. Since I know you don't like the smell of vinegar, citric acid (lemon juice) might work as well.
I tried the lemon juice-baking soda paste. No improvement. So I used the Dremel with some polishing compound. That did the trick.
As I have said, I do not intend to use this for food. Even if I were sure it was food safe A)it weighs too much to be practical and B) I already have a perfectly good mortar & pestle for food. So the next step its to lacquer it. I am having trouble figuring out how to lacquer the pestle,, given its shape.
As the weather is right for it, I have started the lacquering. I finally figured out how to do the pestle. I covered one half (let's call it the bottom half) with painter's tape and stood to up in a jar with some pebbles, to make it stand. I have, so far, sprayed the top half of the pestle and the inside of the mortar.
It is done! Later, that day, I finished the lacquering, as the weather was perfect. I just did one coat, as that was all that was needed for my purpose. So it is now on display, in our China cabinet.