I have been doing repairs and finishes on stringed instruments for years and, for the effect you're trying to achieve, 4est has the right idea. The term for a transparent coat with color (dye) is a "toner". Behlens makes a wide range of toners in spray cans.
The way to proceed would depend a lot on the existing finish. I think some of the Thorens tables may have been oiled walnut. One potential problem no one has mentioned is the possibility that someone has used a furniture polish containing silicone. It's definitely a game-changer! Assuming no silicone, it's possible that you could wipe the plinth down with naptha (lighter fluid) and spray light coats of toner until it's the desired shade, followed by a couple of clear coats. Personally, I would seal it with a couple light coats of a 1 lb. cut of shellac before the toner, but it's not an off-the-shelf product. Depending on the look you're after, you could actually be done at this point. If you want a mirror finish, you got some work to do.
I use strictly nitrocellulose lacquer which, contrary to popular belief, has NOT been banned. Google "guitar refinishing" and you will find endless sources for this wonderful finish.
For a nitro piano black, you should start with a nice flat surface. Rwwear has the right idea for the primer, but once it has been sanded flat, I would proceed differently for nitro. Once you have a good coat of black, you can lightly dry sand to knock off the dust and minor imperfections. Pigmented nitro is not very durable, so you follow that with numerous coats of clear nitro. Then, I highly recommend you let the nitro harden for several weeks before proceeding. Then follow Rwwear's wet-sanding and buffing instructions, but DO NOT follow with another clear coat.
The way to proceed would depend a lot on the existing finish. I think some of the Thorens tables may have been oiled walnut. One potential problem no one has mentioned is the possibility that someone has used a furniture polish containing silicone. It's definitely a game-changer! Assuming no silicone, it's possible that you could wipe the plinth down with naptha (lighter fluid) and spray light coats of toner until it's the desired shade, followed by a couple of clear coats. Personally, I would seal it with a couple light coats of a 1 lb. cut of shellac before the toner, but it's not an off-the-shelf product. Depending on the look you're after, you could actually be done at this point. If you want a mirror finish, you got some work to do.
I use strictly nitrocellulose lacquer which, contrary to popular belief, has NOT been banned. Google "guitar refinishing" and you will find endless sources for this wonderful finish.
For a nitro piano black, you should start with a nice flat surface. Rwwear has the right idea for the primer, but once it has been sanded flat, I would proceed differently for nitro. Once you have a good coat of black, you can lightly dry sand to knock off the dust and minor imperfections. Pigmented nitro is not very durable, so you follow that with numerous coats of clear nitro. Then, I highly recommend you let the nitro harden for several weeks before proceeding. Then follow Rwwear's wet-sanding and buffing instructions, but DO NOT follow with another clear coat.