How to Paint Over Oil-Based Paint

If you’re planning a paint project, proper planning before you start painting helps you complete the job faster and with less frustration. With that in mind, proper planning encompasses multiple considerations, including selecting the right colors, choosing the right materials, getting the necessary supplies and preparing surfaces for a fresh coat of paint. By taking this time up front, you help ensure your painted surface turns out exactly as you envision.

When it comes to choosing the right materials, different types of paint require different types of supplies and techniques. The main paints used in DIY projects include latex paint, oil-based paint, acrylic paint, alkyd paint and water-based paints like our own Real Milk Paint. If your wood surface has an old oil-based paint on it, however, you can’t simply paint over it with other types of paint without some serious preparation of the previously painted surface.

Can You Paint Latex Over Oil-Based Paint?

Painting latex over oil-based paint is a common question—and the answer isn’t a simple yes or no. While it’s technically possible, it’s generally not recommended unless you’re willing to commit to proper prep using the right bonding products. That’s because latex paint over oil paint without proper surface treatment leads to poor adhesion, which results in cracking, peeling, or bubbling.

So, can you paint latex over oil-based paint? While it’s possible, you should only do so if you prepare the surface with either sanding or a bonding primer designed for latex paint.

What happens if you skip the proper prep? The latex paint will form a weak film that quickly fails. This is especially true on high-gloss oil finishes, where new paint can flake off within weeks.

How to Test Surfaces for Latex Paint or Oil-Based Paint

If you’re thinking of using Real Milk Paint in your projects, keep in mind that this water-based paint doesn’t stick to an oil-painted surface. Minwax stains, varnish, enamels and polyurethanes all contain similar ingredients to oil-based paints, and this is why you need to know the difference between oil-based paint and latex paint before starting your project.

First, it helps to recognize the differences between latex paint and oil-based paint. The most obvious difference is that latex paint is water-based paint, while oil paint has a petroleum base. This difference in mediums means you should examine the instructions for the recommended cleanup procedure. If the container says you can clean up with just soap and water, it’s likely latex paint, but if the instructions say you need mineral spirits, or paint thinner for cleanup, you’re likely working with an oil-based paint.

Drying Time Differences Between Oil and Water-Based Paints

Latex and water-based paints like Real Milk Paint tend to dry much faster than oil-based paints. This can be a big advantage if you’re working on a small piece or need a faster turnaround. In contrast, oil-based paints offer longer open times, which can be helpful for large surfaces or intricate work. Understanding these differences can help you choose the right paint for your project timeline.

Materials You’ll Need Before You Start

For a successful paint job, prep is everything. Before you begin, gather your materials based on the type of paint you’re using. If you’re working with Real Milk Paint, have products like EMERGE Cleaner & Degreaser for cleaning and Ultra Bond Adhesion Promoter for use on non-porous or previously painted surfaces.

If you’re working with latex paint, do not use Real Milk Paint additives like Ultra Bond. Instead, choose a bonding primer formulated for latex paint and follow the product instructions carefully.

Also gather painter’s tape, drop cloths, brushes or rollers, paint trays, and fine-grit sandpaper. If you’re planning a detailed or larger project, consider having multiple brushes in different sizes, a roller frame with extra sleeves, and a sturdy ladder if working on vertical surfaces. Having everything ready before you begin helps the project run more smoothly from start to finish.

Can You Paint Over Oil-Based Paint Without Sanding?

While sanding is generally recommended for strong adhesion, there are cases where you can skip it—particularly if the existing finish is smooth, intact, and not high-gloss.

For example, if you’re painting over gloss without sanding, thoroughly clean the surface with Tri-Sodium Phosphate (TSP) to remove waxes and contaminants. If you’re using Real Milk Paint, apply a high-adhesion primer like Zinsser Bulls Eye 1-2-3 Water Based Primer or add Ultra Bond Adhesion Promoter directly to the mixed milk paint to help it grip the surface effectively. For latex paint, use a primer specifically formulated for latex compatibility—Real Milk Paint products are not designed for use with latex.

This approach can also work when painting over polyurethane without sanding, but only if the finish is in excellent shape. Before sanding, scrape off any loose or peeling paint using a putty knife or wire brush. Once the surface is clean, sanding gives the paint a rougher surface to grip onto and fixes surface imperfections. Even when using a bonding primer, a light scuff sand is still recommended to improve adhesion and reduce the risk of peeling—especially on high-use surfaces.

Lead Paint Warning for Older Surfaces

If you’re working with older furniture or walls, there’s a chance the original oil-based paint contains lead—especially in layers beneath the top coat. In these cases, safety is a priority. Real Milk Paint recommends using Soy Gel Paint Remover to encapsulate and lift old paint safely. Always test and follow proper removal practices before proceeding with sanding or repainting.

Priming and Barrier Coats That Bond

Before applying Real Milk Paint or latex over oil-painted surfaces, you’ll need a barrier coat to ensure long-lasting results. This is essential if you plan to paint over oil-based paint with latex.

Extreme Bonding Primer Barrier Coats

If you’re using Real Milk Paint, a bonding primer for oil-based paint such as Ultra Bond can help bridge the oil layer and your milk paint topcoat. For best results, mix Ultra Bond with your first coat of Real Milk Paint at a 3:1 ratio (75% paint, 25% Ultra Bond). This promotes adhesion without compromising the paint’s look or performance. Ultra Bond is not compatible with latex or acrylic paints.

Also worth noting—Real Milk Paint adheres well to latex paint that has cured for 30 days. If it hasn’t fully cured, you may see some cracking, which can be a creative option if you’re aiming for a distressed finish.

Dewaxed Shellac Barrier Coats

Real Milk Paint also adheres to dewaxed shellac, though most hardware-store shellac contains wax. For the best results, order dewaxed shellac from a specialty retailer. Applying milk paint over waxy shellac or uncured latex may result in flaking, which can create an antique look if desired.

Zinsser Bulls Eye 1-2-3 Sealer Barrier Coats

Another option is Zinsser Bulls Eye 1-2-3, a traditional water-based primer. It contains titanium dioxide (pigment) and calcium carbonate, allowing it to be tinted closer to your desired milk paint shade. This primer works well on older plaster or previously treated walls and helps block waxes, silicone, and unknown contaminants.

Whatever you choose, the key is to use the correct primer for oil-based surfaces—skipping this step can lead to premature paint failure, especially when using water-based products.

Finishing Strong: What to Know Before You Paint Over Oil-Based Surfaces

Whether you’re tackling an older piece of furniture or a wall coated in oil paint, knowing how to paint over oil paint gives you the confidence to handle a variety of surfaces. From bonding primers to degreasers like TSP, Real Milk Paint Co. offers everything you need to paint over existing paint successfully.

Our VOC-free, non-toxic milk paint works beautifully on properly prepped surfaces—giving you a natural, durable finish that complements both modern and vintage styles.

Ready to start your project?

Explore our eco-friendly paint and prep products or get in touch with our team for personalized guidance.