Well, lacquer over a plastic is a plastic over another plastic, and I have no problem with that. Lacquer can best be described as "celluloid". You can soak clear photographic film is lacquer thinner or acetone and make your own finishing lacquer. Make a thicker solution and you will have a cellulose glue.
Lou answered the question. To put it another way - a "sealer" is IN the wood, and a "finish" is ON the wood. Sometimes they are the same material. Most of the time they are not.
A "sealer" is a surface preparation before putting a "finish" on top of it. It is sanded back until there is nothing on top of the wood, all of the grain and pores are sealed, and the surface is smooth.
A "sanding sealer" has a lubricant added to the sealer material to make the sanding easier. Since the lubricant is opaque chemical powder, leaving any of it on the wood surface will mask the grain and color of the wood.
Lacquer and CA glue have different properties. CA glue is clear and harder than lacquer. That makes it a good material to fill and harden the wood surface. It also makes a good finish when abrasion and hard use are factors. I think we love it because it is fast rather than for any endearing properties it might have. When a CA finish is done, it's done. Other finishes require waiting longer.
Even though it might be softer than a CA finish, we would still prefer the lacquer finish because it will accent a wood grain and color better than any other finish; and that is because lacquer is the only finish that will give us the three properties of clarity, brilliance, and depth. A CA finish can only give us clarity because it just doesn't exhibit the other properties.
Lacquer will accent the grain and color differences in a polished wood surface as good or better than any oil we can use on the wood. CA won't do this as well by itself, and many of us use Boiled Linseed Oil to help the CA with accenting the grain.
Clarity is what it is, a clear finish without any opacity or light absorbing material in the finish film. Brilliance is the interplay of reflections between the planes within the finish. Depth is the offset between the reflections from the bottom and top surfaces of the film, giving the illusion of depth. To get that reflection off the bottom of the film, the surface has to be smooth, the smoother the better, and that is why we use a "sealer".
Have we answered the question??
