Yes
Yes, as long as the polyurethane is oil-based.
Yes, you can put polyurethane paint over eggshell in latex or eggshell in oil.
Yes, both oil and water-based polyurethanes will adhere well to an item coated with acrylic paint. If it is a polyurethane paint, dull the surface prior to painting. If it is a clear. realize that that oil based polyurethane will impart an amber hue while a water based polyurethane is crystal clear and will not affect the color.
I use oil base enamel with oil base polyurethane. Tip: Make sure you allow it to dry completely before you apply top coat. Good luck.
If you mean an oil based polyurethane, no, it will dry too hard and will chip off over time and normally isn't meant for exterior work. A better option would be to use a 100% acrylic clear polyurethane, paint or solid stain. They are adhesive enough to adhere to vinyl fencing or decking and will flex during freeze/thaw cycles.
Yes, as long as the polyurethane is oil-based.
Yes, you can put polyurethane paint over eggshell in latex or eggshell in oil.
You can apply "oil" based polyurethane over "oil" based enamel, you can also apply "water" based polyurethane over "water" based enamel, never mix the two, there's to much of a chance for problems.
Yes, you can.
yes
Yes, both oil and water-based polyurethanes will adhere well to an item coated with acrylic paint. If it is a polyurethane paint, dull the surface prior to painting. If it is a clear. realize that that oil based polyurethane will impart an amber hue while a water based polyurethane is crystal clear and will not affect the color.
Just stained s door, and no reaction at all.
Because it will impart a yellow cast to the paint surface.
Yes, after allowing a sufficient time for the base to dry.
I use oil base enamel with oil base polyurethane. Tip: Make sure you allow it to dry completely before you apply top coat. Good luck.
No, use heated mineral oil or linseed oil, or a polyurethane sealer.
If a polyurethane varnish (not lacquer) contained linseed oil, it COULD have lead in it - lead is a drying agent for that oil. It was mostly used in paints as a pigment. Varnish has no pigment and it dries by chemical reaction, so most polyurethane varnishes don't need lead.