There are many types of metal that are used in kintsugi. This post will talk about the most common grind which is a fine powder and is called keshifun or keshi in Japanese.
This is what is mostly seen in pieces that are done with real kintsugi and have real gold or silver applied to them. It doesn’t need to be polished but it will take a burnishing if you want to. It is more durable if it is polished but that also makes it shinier. I prefer it matte so I usually don’t polish it. It also doesn’t need an overcoat of lacquer.