How to Thin Oil Paint

Co-authored by Kelly Medford and Janice Tieperman

If you’re starting a new art or home improvement project, you might be using oil-based paints to get the job done. While oil paint looks beautiful on a finished product, it can be a bit difficult to apply at first. If you’re working on a residential or commercial painting project, mix small amounts of turpentine or mineral spirits with the rest of your paint. If you’re an artistic painter, mix linseed oil and mineral spirits together to help apply your paint more smoothly to a canvas. With the right ratio of paint and thinning agent, you’ll be on your way to creating a vibrant final product.

Method 1

Method 1 of 2:

Using Paint Thinner for Interiors and Exteriors

1
Set up your painting supplies in a well-ventilated area. Slide on a respirator or breathing mask before working with any kind of paint thinner. Since these products give off harsh fumes, you don’t want to inhale any paint thinners directly. Additionally, set up a box fan that’s facing away from your painting area, so any fumes can swiftly leave the room.^{[1]
X
Research source}
- If you’re painting outside, you should still wear a respirator or safety mask.
2
Mix a 2:1 ratio of oil paint and turpentine for a thicker paint application. Pour your desired amount of paint into a painting tray. To give your paint a slightly thick consistency, combine 1 cup (240 mL) of turpentine or mineral spirits with 2 cups (470 mL) of oil-based paint.^{[2]
X
Expert Source

Kelly Medford
Professional Artist
Expert Interview. 10 March 2021} Use a paint stirrer to mix the ingredients together so the paint has an even consistency.^{[3]
X
Research source}
- Always use a 2:1 ratio of paint to paint thinner when creating a thicker mixture.
- These ratios work best for widespread paint application, like the exterior of a home.
Advertisement
3
Stir in more thinner to water down the paint. After pouring your paint into a tray, pour in a larger amount of turpentine or mineral spirits to dilute the mixture. For a thinner paint job, add in 2 cups (470 mL) of paint thinner into 1 cup (240 mL) of oil paint. Using a paint stirrer, mix these 2 substances together to create a watered-down base for your project.^{[4]
X
Research source}
- Use a 1:2 ratio of oil-based paint and thinner whenever you make a thinner mixture.
- Thinner coverage can work well for exterior painting projects that involve a lot of whitewashing.
- Don’t add too much thinner at once. You can always make adjustments to your mixture later!
4
Test out a small amount of paint before covering an entire surface. Before embarking on your project, try combining a small amount of paint and thinner together using your desired ratio. Use a small brush to paint over a tiny spot in your project, so you can see if you like the coverage or not. If the paint job looks good, continue painting over the rest of the surface.^{[5]
X
Research source}
- Add thinner in small, tablespoon or milliliter increments when making adjustments to your mixture.

Method 2

Method 2 of 2:

Combining Oil and Mineral Spirits for Art Projects

1
Mix 1 part of linseed oil with 2 parts of mineral spirits in a jar. Pour 1 tablespoon (15 mL) or so of linseed oil into a small glass container to serve as the base for your medium. To thin out the oil, add 2 tablespoons (30 mL) of mineral spirits into the jar. Use a palette knife or other thin tool to stir these ingredients together. Store the medium in a small glass container.^{[6]
X
Research source}
- Any drying oil will work for your medium, like walnut oil. Avoid using non-drying oils in your mixture, like coconut oil.
- If you anticipate needing more oil medium, feel free to increase the amounts in your ratio.
Did you know? A medium is a substance that lets you apply your paint to a surface in a unique, artistic way.
2
Add small, even amounts of oil paint onto your palette. Use a palette knife to scoop a grape-sized amount of different-colored paints onto your palette. Keep these paints at least 1 in (2.5 cm) apart so the colors don’t bleed together on accident.^{[7]
X
Research source}
- Always wipe off your palette knife before dipping into a different paint.
3
Add 1-2 drops of your medium into each paint color. Take an eyedropper tool and squirt a couple drops of diluted oil into each mound of paint. Ideally, try squeezing the oil into the center of the paint, so it will be easier to mix in. Try adding the same amount of medium to each color, so your paint application looks consistent in your final product.^{[8]
X
Research source}
- Don’t add too much oil medium at once. You can always add in more thinning agent if the paint is still too thick.
4
Stir the ingredients together with a small palette knife. Take a palette knife and spin it through each paint color. Work the tool in round motions, so all the paint mixes in with the drops of oil medium. Continue flipping and rotating the knife until the paint is thoroughly mixed with the oil, and has a consistent texture throughout.^{[9]
X
Research source}
- Wipe off the palette knife before stirring other paint colors.

Expert Q&A

Question

How do I make oil paint runny?

Kelly Medford
Professional Artist
Kelly Medford is an American painter based in Rome, Italy. She studied classical painting, drawing and printmaking both in the U.S. and in Italy. She works primarily en plein air on the streets of Rome, and also travels for private international collectors on commission. She founded Sketching Rome Tours in 2012 where she teaches sketchbook journaling to visitors of Rome. Kelly is a graduate of the Florence Academy of Art.

Kelly Medford

Professional Artist

Expert Answer

Mix your oil paint with a little bit of turpentine to make it thinner and easier to use.