paints based on oil
Yes, you can apply oil-based polyurethane over oil-based stain.
paints based on oil
Castile is olive oil based.
No, latex paint is water-based, not oil-based.
Acrylic paint is water-based, not oil-based or latex-based.
oil based
Yes, polyurethane is typically oil-based.
I am fairly certain that it is oil based. It is pretty easy to find that on google...
Yes. Clean and degloss the oil based paint, apply an oil based primer, then apply the water based paint.
Is the paint you're using water-based or oil-based?
The polyurethane being used is either oil-based or water-based.
Yes, Varathane stain is oil-based.