How To Paint Over Oil Based Paint

Water-based acrylic and latex paints are relatively new on the painting scene. If you are remodeling a house or painting a piece of furniture from the 1980s or earlier, there is a good chance you are working with an oil-based paint. I have several methods to help you complete your project and avoid paint that quickly cracks or peels.

Checking for Oil Based Paint

Oil-based paints take anywhere from 7-30 days to cure. Cured oil-based paint is extremely durable and glossy. Even though this paint emits high levels of VOCs when applied and requires harsh chemicals to clean up, it is still in use today. In modern applications it is most commonly applied in high-traffic areas including cabinets, shelves, casings, and moldings.

To determine if you are working with an oil-based paint:

1. Dampen a clean, white cloth with rubbing alcohol. 
2. Scrub a discrete area of your project. Rubbing alcohol will break down polymers in water-based paints which will discolor your rag.
3. If your rag takes on the color of the paint you are rubbing, it is a water-based paint. If the alcohol has no effect, it is likely an oil-based paint.

Painting Oil Paint Over Oil Based Paint

One of the easiest ways to paint over oil-based paint is to repaint with an oil-based paint. Oil-based paints have a beautiful glossy finish and will bond easily with the existing oil paint. This is the most straightforward way to repaint your project. Painting over oil-based paint with another coat of oil-based paint does not require sanding.

To use oil-based paint to paint over an oil-based paint:

1. Thoroughly clean the surface you plan to paint. TSP is a helpful cleaning agent but will require gloves, goggles, and a respirator.
2. Allow surfaces to completely dry.
3. Due to VOC emissions from oil-based paints, put on a respirator and goggles before applying oil-based paint. Ensure your work area is ventilated.
4. Using a natural bristle brush, apply oil-based paint. Keep a wet edge and work in smooth, steady strokes. Alternatively, you could use a good interior paint sprayer to apply the oil-based paint.
5. Allow paint to dry according to manufacturer instructions before applying a second coat, usually 24 hours.

Of the options described within this article, painting over oil-based paint with another layer of oil-based paint will take the longest, especially if two coats are necessary. 

Reconsidering Oil-Based Paints

There are drawbacks to oil-based paints. Oil-based paints require ventilation and respirators. Drying times and curing times are significant.

Oil-based paints tend to come in smaller can sizes and require mineral spirits to clean up. UV rays also affect the color of the paint over time.

The traditional reason for choosing oil-based paints within the trades is its durability. Water-based paint technology has improved dramatically within the past decade. New water-based paint is not only much more flexible than oil-based paints but can also match oil-based paint’s durability.

Painting Alkyd Paint Over Oil Based Paint

While often lumped in with oil-based paints, alkyd paint does not contain oil. Alkyd paint uses a synthetic resin as a binder to hold the paint’s pigment and thinner together. As the alkyd paint’s thinner dries out, it leaves behind an incredibly strong bond. Alkyd paints tend to go on thicker, sometimes requiring fewer coats.

Alkyd is often used on metal and wood, indoors and outdoors, particularly in high traffic areas. The function and application of alkyd paint is very similar to oil-based paints. Alkyd paint can be applied to oil-based paint as soon as the oil-based paint is ready for a recoat.

To apply alkyd paint over your oil-based paint:

1. Your painting surface should be wiped clean of all dirt and grease.
2. Put drop cloths or plastic sheeting around your work area.
3. Put on respirator and goggles due to VOC emissions of alkyd paint.
4. Ventilate the area.
5. Paint with a natural bristle brush in even strokes.
6. Recoat per manufacturer instructions, usually 16 hours.

Questioning Alkyd Paints

There are a few drawbacks to alkyd paints.

• Traditional alkyd paints are more toxic to the environment than water-based paints.
• Alkyd paints drip from brushes more easily than oil-based or latex paints.
• Cleaning up alkyd requires mineral spirits which introduces another potentially dangerous chemical to your project.

A recent advancement in alkyd paints is the introduction of water-based alkyds. Its introduction to the market means more time is still needed to evaluate its long-term durability and environmental impact.

If you have a strong preference for alkyd enamels, new water-based formulations are worth checking out.

Painting Water-Based over Oil Paint

Water-based paints dominate the market currently. Low VOCs make it more family friendly. It dries more quickly than alkyd or oil-based paints, and it has great flexibility. Early iterations of water-based latex paint had poor reliability.

As the formulas have advanced and understanding of best practices for applying latex paint have improved, water-based latex paint has become the industry standard.

Painting over oil with water-based paint is possible but requires more work than using an oil-based or alkyd paint.

To paint over oil-based paint with water-based paint:

1. Scrub the area you wish to paint with a slightly moistened sponge.
2. Allow the area to dry.
3. Gently sand away the glossy finish of the oil-based paint using fine grit sandpaper.
4. Wipe away dust and detritus from the paint surface. I recommend using TSP for this wipedown but be sure to wear gloves, goggles, and a respirator as you do.
5. Give time for the project to dry.
6. Apply 1 or 2 coats of water-based primer, following manufacturer instructions for the primer dry and recoat time. Add the second coat if color or imperfections from the oil-based layer are still visible.
7. Apply coats of water-based paint as necessary with a synthetic fiber brush following manufacturer instructions. Latex normally requires four hours between coats while acrylic can be as short as 10 minutes.

Painting over oil-based paints with water-based paints is possible. It requires a few more steps. Those steps require labor, but the comparative safety of water-based paints is hard to overvalue.

Also, water-based latex paint tends to be cheaper than oil-based or alkyd paint. This more involved method may also save you a few dollars.

Explaining Water Based Paints

There are two common types of water-based paints: latex and acrylic. The composition of both types is very similar. Water-based paints all contain a ratio of pigment to binder to thinner. The differences in these ratios is primarily what separates latex and acrylic paints.

Pigment is what gives paint color. Binders hold the pigment together after the thinner dissipates. Thinners largely determine the viscosity of paint and as thinners evaporate, paint hardens or dries. In water-based paints, acrylic is the binder and water is the thinner. 

Water-based acrylic paints tend to have higher proportions of acrylic binders than latex paints. Latex paints tend to have a higher proportion of thinner. This means that water-based acrylics have brighter color and durability but dry quickly.

They also can be quite the challenge to get off of wood once dried.

Latex paints dry more slowly and are cheaper due to higher water content. However, latex paints have less durability than acrylic. You can spray latex paint relatively easily, provided you thin it first, making it a favorite for quick jobs.

Environmental and safety concerns lead me to recommend water-based paints for most projects. Rapid advancements in technology to meet consumer desires and demands has led to great innovations for paint manufacturers over the past few years. 

There is promise that more sustainable, less harmful paints will continue to be developed.

Conclusion

Painting over oil-based paints is possible. There are three solid options available to you. Each method requires thorough cleaning and patience between coats. I recommend painting over oil-based paints using a water-based paint. If your painted project will primarily be outdoors, use vibrant water-based acrylic paint. If you are working on interior walls, consider water-based latex.