How to Thin Oil Paint? - 4 Methods to Thin Paint

Oil paint straight from the tube can be too thick for smooth application. It can make blending, layering, and fine details difficult.

Without proper thinning, your paint may dry with unwanted texture, appear muddy, or even develop cracks over time.

To thin oil paint effectively, use solvents like mineral spirits for a fast-drying, matte finish, oils like linseed or walnut oil for a glossier, slow-drying effect, or specialized mediums to control both viscosity and drying time.

Why Thin Oil Paint?

Thinning oil paint makes it easier to apply, improves blending, and helps with layering. Thick paint can be hard to work with, leaving rough brushstrokes or drying unevenly. By thinning it, you get smoother application, better control, and a more polished final result.

It also prevents common problems like cracking, dull spots, and uneven drying. Oil paint follows the fat-over-lean rule, meaning each new layer should have more oil than the one beneath it. This keeps the painting stable over time.

"My general process is spontaneous. There is always a reason that leads me to begin with a certain method, but I never follow the same process." - Guo Hongwei, a contemporary Chinese artist.

Different thinning methods affect drying time and finish:

• Solvents (e.g., mineral spirits, turpentine) make paint dry faster with a matte look—great for base layers.
• Oils (e.g., linseed, walnut, safflower) slow drying and create a glossy, rich finish—ideal for top layers and blending.
• Mediums help adjust both viscosity and drying time, giving you more control.

Thinning is also key for techniques like glazing, underpainting, and smooth color transitions. Next, we’ll cover the best ways to thin oil paint so you can find the right method for your painting style.

Methods for Thinning Oil Paint (With Step-by-Step Guides)

There are three main ways to thin oil paint: solvents, oils, and mediums. Solvents like mineral spirits or turpentine break down the paint for a fast-drying, matte finish, making them ideal for underpainting. Oils like linseed, walnut, or safflower oil increase flow and slow drying time, creating a smoother, glossier finish. Mediums such as Liquin or Galkyd adjust both viscosity and drying time, offering more control for different techniques. Below, we’ll go through each method in detail, including when and how to use them.

Thinning Oil Paint with Solvents (Best for Early Layers & Fast Drying)

Solvents are the most effective way to thin oil paint quickly and thoroughly, making the paint more fluid and easier to spread. They evaporate as the paint dries, leaving a matte finish and speeding up drying time. This makes them ideal for underpainting, base layers, and blocking in colors. However, they should be used sparingly in later layers to avoid cracking or sinking in.

Common Solvents for Thinning Oil Paint

• Mineral Spirits – A milder, low-odor option that thins paint while maintaining color stability.
• Odorless Mineral Spirits (OMS) – Refined to remove strong fumes (e.g., Gamsol, Turpenoid).
• Turpentine – Traditional but strong-smelling; dries fast but requires good ventilation.

How to Thin Oil Paint with Solvents

1. Pour a small amount of solvent into a container with a lid to minimize fumes.
2. Dip your brush lightly into the solvent—too much can overly dilute the paint.
3. Mix the brush into your paint on the palette until you reach the desired consistency.
4. Apply the thinned paint to your canvas, keeping it in early layers.
5. Allow layers to dry completely before applying oil-rich paint on top.

Tip: Use artist-grade solvents (e.g., Gamsol) instead of hardware store versions to reduce toxicity.

Thinning Oil Paint with Oils (For Richer Layers & Slow Drying)

Using oils to thin paint keeps colors vibrant, improves blending, and prevents cracking, making it ideal for later layers, glazing, and smooth transitions. Unlike solvents, which evaporate completely, oils remain in the paint, slowing the drying process and creating a glossy, flexible finish.

Common Oils for Thinning Oil Paint

• Linseed Oil – Most common; moderately slows drying and can slightly yellow over time.
• Walnut Oil – Slower drying than linseed oil; enhances color vibrancy with less yellowing.
• Safflower Oil – Even slower drying; non-yellowing, often used in lighter colors.
• Poppy Oil – The slowest drying; ideal for blending but may have long-term stability concerns.
• Stand Oil – Thickened linseed oil with a syrupy consistency; creates smooth, enamel-like finishes.

How to Thin Oil Paint with Oils

1. Pour a small amount of oil directly onto your palette—no need for a separate container like with solvents.
2. Mix a small amount of oil into the paint using a palette knife or brush. Oils are more concentrated than solvents, so a little goes a long way.
3. Blend thoroughly until the paint reaches the desired consistency. For glazing, use more oil; for standard layering, use less.
4. Apply in mid-to-late layers, ensuring each layer contains at least as much or more oil than the previous one (fat-over-lean rule).
5. Let layers dry completely before adding additional paint to avoid smudging or tackiness.

Tip: If you want smoother flow without over-thinning, try Stand Oil, which thickens the paint slightly while improving spreadability.

Since oils retain flexibility and prevent cracking, they are perfect for rich, blended layers and controlled drying times. 

Thinning Oil Paint with Mediums (Customizing Drying Time & Viscosity)

Mediums allow you to adjust drying time, viscosity, and texture while keeping the paint stable. Unlike solvents, which evaporate completely, mediums remain in the paint film, preventing sinking in and maintaining color vibrancy. They are often used for layering, glazing, or modifying paint consistency without over-diluting it.

Common Mediums for Thinning Oil Paint

• Liquin (Winsor & Newton) – Speeds up drying and creates a smooth, even flow.
• Galkyd (Gamblin) – Adds gloss and improves paint adhesion while drying faster.
• Neo-Megilp (Gamblin) – A soft, gel-like medium that holds brushstrokes.
• Solvent-Free Gel (Gamblin) – A non-toxic alternative that increases flow and flexibility.

How to Thin Oil Paint with Mediums

1. Add a small drop of medium directly to the paint on your palette. Unlike solvents or oils, you don’t need a separate container for dipping.
2. Mix gradually with a palette knife or brush, ensuring even distribution.
3. Use sparingly—too much medium can make the paint overly slick or difficult to control.
4. Apply as needed, adjusting based on whether you want thin glazes (more medium) or subtle blending (less medium).
5. Let each layer dry fully before applying the next if using fast-drying mediums like Liquin or Galkyd.

Tip: If you prefer thicker brushwork, try a gel-based medium like Neo-Megilp instead of a liquid one.

Because mediums modify the paint’s texture without breaking down its structure, they are a versatile alternative to traditional solvents or oils.

Mixing Solvents & Oils for Custom Results

Combining solvents and oils allows you to fine-tune your paint’s viscosity, drying time, and finish. Solvents evaporate quickly, thinning the paint for underpainting and base layers, while oils slow drying and add flexibility for later layers. By mixing both, you can create a balanced medium that adjusts to your needs—fast-drying yet smooth, fluid yet stable.

Common Solvent & Oil Combinations

• Mineral Spirits + Linseed Oil → Balanced drying time, good for layering.
• OMS (Odorless Mineral Spirits) + Walnut Oil → Smooth blending with less yellowing.
• Turpentine + Stand Oil → Glossy, slow-drying medium for controlled brushwork.
• OMS + Safflower Oil → Ideal for slow-drying techniques and delicate color transitions.

How to Mix Solvents & Oils for Thinning Paint

1. Use a 2:1 or 3:1 ratio of solvent to oil for base layers (more solvent = thinner paint).
2. For mid-to-late layers, reverse the ratio (more oil than solvent) to follow the fat-over-lean rule.
3. Mix in a small jar or directly on the palette to control consistency.
4. Stir or shake the mixture well before dipping your brush.
5. Test the mixture on your canvas before applying broadly to ensure proper drying behavior.

Tip: If you want glazing effects with more control, try a 50/50 mix of OMS and Stand Oil for a slow-drying, glossy finish.

By adjusting the solvent-to-oil ratio, you can customize how your paint behaves, ensuring stability, smooth application, and long-lasting results.

Conclusion

Thinning oil paint isn’t just about making it easier to spread—it’s about control. The wrong consistency can lead to cracking, dull patches, or difficulty blending, while the right thinning method ensures smooth application, proper drying, and a long-lasting finish.

​Art critic Peter Schjeldahl once commented on Sherron Francis's work, stating, "Her paintings, stained and brushed to a suavely grainy texture, each float an area of warm, soft color in a somewhat less-intensely colored field."

One mistake many oil painting beginners make is over-thinning with solvents, which can weaken the paint film and cause it to look patchy over time. On the other hand, using too much oil can slow drying excessively, making it hard to layer effectively. The key is finding the right balance based on your technique, whether it’s underpainting, glazing, or impasto work.

A lesser-known fact is that some traditional painters used egg yolk as a natural emulsifier to modify oil paint consistency—an early form of what we now call tempera painting. While that’s not a common practice today, it highlights how artists have always experimented with different materials to control paint behavior.

If you want to see how professional artists approach oil painting, take a look at our custom oil painting gallery, where some of the experts who contributed their insights to this guide showcase their work. Their mastery of color, layering, and paint consistency is a great source of inspiration for any painter looking to refine their technique.