For artists, there are a number of ways to thin oil paint. However, the best thinning method will depend on how thin you want to make your paint, your painting technique, and how much gloss you want to achieve. So what are some of the best ways to thin oil paint?

Thinning oil paint with solvents such as mineral spirits achieves lower viscosity with moderate drying time and a matte appearance. Thinning with natural oils such as linseed oil achieves higher viscosity, slow drying time, and glossier results.

There are many other options besides the ones listed above. Let's look at some of these options and what you need to know about each one. See below the table for detailed information.

Thin Oil Paint with Solvents

The most basic way to thin oil paint is by using a solvent such as mineral spirits or turpentine. Solvents will thin the paint very rapidly and thoroughly and are low viscosity, which means they have a more watery consistency. You can thin the paint with a small amount to make it buttery, or thin it to a soup-like consistency so you can quickly and easily cover your canvas and fill in any texture.

Thinning with solvents will dry the paint faster than using natural oils such as linseed or safflower oil. The paint will also have a more matte appearance when it dries. Also, most solvents usually cost less than other mediums and oils.

Thinning your initial layers with a solvent means you don't have to worry about violating the fat over lean rule when adding subsequent layers of paint. The fat over lean rule says that any subsequent layers of paint need to have at least as much or more oil content than the previous layers in order to prevent sinking in. Sinking in is when dull spots appear on your painting after it has dried. Click here to see my article on how to fix sinking in problems.

The above consideration means that you should only thin with mineral spirits on your first couple layers of paint. Each additional layer should have less solvent than the previous layer to ensure there is more oil in that new layer.

Do not thin your oil paint with a solvent if the previous layer(s) consists of thick and/or oily paint. This will cause massive sinking in and even cracking down the road. Also, avoid thinning your paint with solvents if you use a glazing technique. Oil or oil-based mediums are better suited for glazing.

One of the big drawbacks to using solvents to thin oil paint is the fumes solvents release. These fumes can be harmful to breathe in over extended periods of time. If you are very sensitive to solvents you may not be able to use them at all. If that is the case, click here to check out my article on oil painting without solvents.

When using solvents, it's recommended you use artist-grade solvents such as Gamsol or Turpenoid. Unlike mineral spirits you buy at the hardware store, artist-grade mineral spirits do not contain any additives, and they have less of a smell. That said, I will use hardware mineral spirits when I'm doing oil sketches outside (plein air painting). I don't intend to sell these sketches or even display them, and when I'm outside the fumes don't bother me as much.

Another solvent you can use is turpentine. Made of pine tree resin, turpentine has been around longer than mineral spirits, which is derived from petroleum distillates. Turpentine will have the same effect on oil paint as mineral spirits, but many artists find the fumes from turpentine more difficult to tolerate. You may also find the price of turpentine to be higher than mineral spirits.

How to Mix Solvents with Oil Paint

To thin your oil paint with a solvent, pour some solvent into a small or medium-sized jar. Make sure whatever jar or container you use has a tight-fitting lid to prevent excess fumes and evaporation. I like to use a very small container because the solvent can quickly become polluted. Using a small jar means only a small amount of solvent will be polluted and can be easily replaced with clean solvent.

Dip your brush into the solvent. If you want to thin your paint only slightly, then dip just the tip of your brush into the solvent. If you want to thin your paint to a more soupy consistency, dip most of your brush into the solvent. Bring your brush over to your paint and mix it together on your palette. Repeat as necessary until the paint becomes the desired viscosity.

You can also sprinkle solvent into the paint on your palette, especially if you want to thin a large amount of paint.

Thin Oil Paint with Oils

The above line sounds a bit obvious and redundant, but there are some important things you need to know about thinning your oil paint with oils.

Thinning your paint with oil results in a higher viscosity and dries glossier than thinning with solvents. But as implied in our above conversation about the fat over lean rule, you want to avoid thinning your first layers of paint with oils unless you plan to add at least as much, if not more oil to your subsequent layers to prevent sinking in. Thinning your subsequent layers with oil is a great way to increase the "fat" content of your paint and prevent sinking in.

So if you like to work with thin paint, thin your first layer or two with a solvent such as mineral spirits, then thin your subsequent layers with oil or an oil-based medium. You can also use oils for glazing techniques. Let's look at some of the different oils and their characteristics.

Linseed Oil

The most widely used oil for oil painting is linseed oil. Derived from flax, linseed oil is the most stable oil with moderate drying time, around 5 days or so. Linseed oil dries by forming a top skin and going from there. The one problem with linseed oil is that it can yellow over time. So if you want to thin a cooler, lighter value color such as white, you may want to use a different type of oil.

Walnut Oil

Used for hundreds of years, walnut oil is great because it's very resistant to yellowing and cracking and it dries slower than linseed oil. Some paint manufacturers use walnut oil almost exclusively. Walnut oil can also make your colors appear to be more intense.

Safflower Oil

Safflower oil dries even more slowly than linseed oil. Rather than drying by first forming a top skin, safflower oil dries more evenly, which can cause it to have a sticky feeling during the drying process. It also doesn't yellow as much as linseed oil. Some have questioned safflower's long-term stability, but this is unwarranted as centuries-old paintings have shown it holds up very well.

Poppy Oil

If you want to really slow down your drying time then poppy oil is the way to go. Bear in mind there are concerns about its long-term stability and you should avoid using it in your initial layers.

Stand Oil

Stand oil is essentially linseed oil that has been heated. The result is a thicker, higher viscosity oil that dries faster than regular linseed oil. It also has better color retention since oxygen is what causes yellowing and stand oil requires less oxidation time to dry.

How to Mix Oils with Oil Paint

Mixing oils with oil paint is a similar process to mixing solvents with oil paint. Pour some into a small jar. With oils it's not imperative that the jar has a lid as fumes and evaporation will not be an issue (unless you just don't like the smell). Dip your brush into the oil and then mix it with your paint. Once again small jars are best so you can replace polluted oil with clean oil more often and with less waste.

You can also pour the oil directly onto your palette and mix it that way.

Thin Oil Paint with Mediums

Besides solvents and natural oils there are a wide variety of manufactured mediums you can use to thin your paint. Many of these mediums are a combination of some type of oil-based substance such as petroleum distillates with solvent. While there are many on the market, we will discuss a few of the more popular ones here to get you started.

Galkyd

Galkyd made by Gamlin is one of the primary mediums I use when oil painting. It's a petroleum distillates-based medium that has a somewhat high viscosity. It does a great job of adding flow and will set-up and dry somewhat quickly (usually in a day) with a glossy finish. You can also thin Galkyd with Gamsol or other artist-grade mineral spirits to decrease its viscosity and reduce gloss.

There are several versions of Galkyd available such as Galkyd Lite, which is lower viscosity and dries less glossy, and Galkyd Slow Dry, which dries slower and is also less glossy. It's recommended you don't mix solvents with Galkyd Lite or Galkyd Slow Dry.

Liquin

Also derived from petroleum distillates, Liquin, made by Winsor & Newton was originally made to be a modern sustitute for Maroger medium (see below), but without the need to deal with lead. Liquin functions in the same way as Galkyd and is widely used by artists. They also make a Liquin Gel that has alkyd resin added to give it a thicker consistency.

How to Mix Mediums with Oil Paint

To use Galkyd or Liquin, pour a small amount onto your palette or into a small cup, dip your brush into it, then mix it into your paint. You can mix a small amount for impasto techniques or a larger amount for glazing.

Thin Oil Paint with Gels

Having a very high viscosity, gels are great if you want to paint with a more impasto technique (thick paint application). While they will not thin your paint to the same degree as its more liquid counterparts, gels will still allow you to more easily spread the paint across the canvas and will give it more gloss when it dries.

Maroger Medium

Essentially consisting of lead cooked with linseed oil, Maroger was developed by Jacques Maroger. Jacques discovered this medium that was believed to be used by the Old Masters. This medium is incredibly versatile. When it's exposed to open air and kept still, it retains its jelly-like consistency, but when it's disturbed it becomes more liquid, only to revert to its more solid form once you stop disturbing it.

This makes it great for slightly thinning oil or for creating more impasto brush strokes with ease. It gives you ample time to manipulate the paint but will stiffen fairly quickly and usually dries overnight. Just be careful if you use traditional Maroger medium as it will contain lead which is toxic.

Neo-Megilp

If you want to have the working characteristics of Maroger medium but without the lead, try Gamblin's Neo-Megilp. It's a gel-like medium that dries a little less glossy than other mediums but doesn't have the higher toxicity of traditional Maroger.

Other Gels

Other gels on the market include Gamlin's Solvent-Free gel as well as Rublev's Epoxide Oil Gel, Walnut Oil Gel and Oleoresgel.

Combining Solvents and Oils

Combining solvents and oil or oil-based mediums can give you a wide variety of results. Say you want a low-viscosity medium that dries quickly with gloss. You can mix mineral spirits with stand oil. If you want a low-viscosity medium that dries with gloss but more slowly, try mixing mineral spirits with safflower oil.

All of Gamblin's products are formulated to work with each other. But if you are working with another brand of medium, be sure to check the manufacturer's recommendations on what can be mixed with that particular medium.

This is by no means an exhaustive list, but hopefully it will get you started with some ideas on how to thin your oil paint.

Jason Tako is a nationally known fine artist who specializes in western, wildlife, plein air, and Historical Native American subject matter. He spent his learning years sketching the wetlands and wooded areas of rural Minnesota. He has been featured in Plein Air Magazine and Western Art Collector Magazine and he was the Featured Artist for the 2020 Southeastern Wildlife Expo. See his work at www.JasonTako.com and his demonstrations on his YouTube Channel.