As long as you sand & prime first, in most cases just latex primer applied before painting with the latex paint. If the old paint is really old, be careful about sanding, it may contain lead.
Not directly. You will need to use a primer made to adhere to oil and will accept a latex topcoat.
Yes, but you can not put latex over oil without a primer coat between.
Yes, you can put polyurethane paint over eggshell in latex or eggshell in oil.
you can paint over latex paint with latex enamel.
No, you either need to really rough up the oil paint with fine sand paper, or put a base coat on before you paint with your Latex paint. If you don't your Latex paint won't adhere.
Just paint it on if the latex is adhering well.
You can not put oil paint over latex paint. Oil is a rigid coating and latex is a flexible coating. When you put a rigid coating over something that is flexible the rigid coating cracks off.
Not directly. You will need to use a primer made to adhere to oil and will accept a latex topcoat.
Yes, but you can not put latex over oil without a primer coat between.
Yes, you can put polyurethane paint over eggshell in latex or eggshell in oil.
you can paint over latex paint with latex enamel.
No, you either need to really rough up the oil paint with fine sand paper, or put a base coat on before you paint with your Latex paint. If you don't your Latex paint won't adhere.
You can use either a water or oil-based paint over a latex primer.
yes but you cannot put latex on top of oil based surfaces You actually are NOT advised to put oil over latex surfaces, which is why you're supposed to prime will an oil-based (alkyd) primer. Latex and Polyurethane should always have a layer of oil-base beneath it.
You can always paint latex ( water based )over an oil based paint as the latex just dries on the surface. However don't paint an oil based over a latex paint. Oil based paints need to absorb into the wood or other surfaces or it will just dry and flake off. For more information on the differences and when or not to use a latex or oil paint please see the following article. . http://www.ehow.com/how_4713170_between-latex-oil-base-paint.html
No you can not.
You need to prime first, with a primer that adheres to oil paints, and to which latex can adhere. You may even want to sand the oil-painted surface lightly to scuff it for better primer adhesion. Painting latex straight on top of oil paint will result in peeling.