hi there! We bought an old condo, and it has a built-in cupboard of sorts, but it looks like this: (see photo). Any ideas on how to clean up all these scratches would be greatly appreciated! Thanks
When refinishing old surfaces like that, I have had great results finding the right compound to do what is called I think, re-amalgamation. It is when the proper solvent or compound I called it earlier, is used to melt the finish on the surface and allowed to dry again. It will remove some of the finish, or perhaps even most of it if too much is applied and wiped back off, but it requires no sanding, but you will need a respirator for the fumes. This saves the patina of the surface and will remove all the glass rings and minor scratches that was on the surface. If there are deep scratches it will not remove them, but it may color them in a bit so they are not so noticeable.
The finishes used typically are shellac and lacquer. Shellac can be removed with denatured alcohol I think, lacquer is cut with lacquer thinner.
If you really want it all clean and pristine and brand new looking, the sanding is the best way to go since the only way to get rid of deep scratches is by sanding, unless you want to try your hand at using lacquer sticks. Those are a heat melt-able filler that come in numerous colors to blend in with the color of the wood.
You have got your work cut out for you. in my opinion that thing needs a complete refinishing. You’re going to want to use a stripper such as a citrus-based stripper and strip off all of the old varnish. Once all the varnish is stripped off then you’re going to want to sand the wood, there appeared to be some deep scratches so you’re going to want to start with a heavy 80 grit sandpaper and work your way up to a fine 320 grit.
If you can remove the cupboard and work on it in another space you will avoid all of the dust that this will create in your home. If not you will need to use some painters plastic and tape/tent off this area of your home so that it will contain the dust and keep it from traveling throughout your house. If you can use a sander that has a vacuum attachment for a shop vac that will also help minimize dust.
Once you have the unit stripped and sanded and the dust cleaned off with a tack cloth you are then ready to stain it any color you like and finish it in the finish of your choice.
I don’t have the time to write a book for you to read about how to refinish furniture but there is this thing called the Internet and if you spend several days researching and learning and watching YouTube videos you’ll gain a good understanding of what is required.
Another option and I am hesitant to say it because I believe that good quality Wood furniture should be refinished and not painted, is to use someone wood filler in all of the scratches sand it smooth and paint it.
Once you are ready to refinish it you could go over to the woodworking stack exchange and ask for advice on staining and finishing wood furniture.