How to Paint Oil-based Paint Over Latex Paint
Can an oil-based paint be used over a surface already painted with latex paint? The truthful answer to this question is that you shouldn’t paint an oil-based product directly over latex paint, but it can be done if a sealing coat is used to separate the layers. Because latex paint has built-in flexibility, it doesn’t make the ideal base for oil paint, which has a hard finish. It’s also far trickier to achieve a good result if the latex paint is relatively new. The task requires paying attention to preparation, which is the key to all successful DIY jobs.
Step 1 – First Stage of Sanding
Due to the stretchy nature of latex paint, an oil-based alternative won’t adhere properly if it is applied directly. That’s why it’s important to remove as much of the latex product as possible. This step is actually the single most important part of the whole process, so it’s well worth applying yourself to creating a suitable application surface if you want to achieve results that will last and look professional.
P80 grit sandpaper is fairly coarse so it is ideal for cutting through the existing finish on varnished and latex painted surfaces. Use a sanding block with the paper wrapped around it and methodically sand the entire area. You want to achieve more than just a light key up with this process so aim to get the surface looking completely matte. Any remaining shiny areas will cause problems later on when it comes time to apply the oil-based paint.
Step 2 – Second Stage of Sanding
Finish sanding using 150 grit sandpaper to achieve a completely smooth surface. When the area is completely sanded, sweep away any residual dust. Wipe the area with a damp cloth and allow it to dry thoroughly.
Step 3 – Mask the Area to Protect Surroundings
Mask edges to protect adjoining walls or features and to ensure that you achieve a neat cut-in when the final coats of paint are applied.
Step 4 – Apply a Water-based or Acrylic Primer
Apply a coat of your chosen water-based or acrylic primer. Because water and acrylics are compatible with both latex and oil-based paints, they make an ideal isolating surface for this task. In effect, the primer will be sandwiched between the latex paint and the oil topcoat. When the primer is thoroughly dry, apply a second coat to further isolate the original surface. You want to ensure that all traces of the old latex paint have been completely covered.
Step 5 – Apply an Oil-based Top Coat
Apply a thin coat of your chosen oil-based topcoat. When this is dry, appraise the situation. If need be, apply a further coat to ensure maximum coverage. Remove all masking tape while the paint is still tacky to avoid tearing the paint.