Types of Mediums Extended: Oils, Thinners, Mixtures, Questions etc.

This post has been rewritten on my new website here: 

https://www.katherinegriffinstudio.com/post/oil-painting-basics-what-is-an-oil-painting-medium

In this post I will describe at length: what a medium is, primary oil medium binders, primary thinners, how to make basic mixtures, and non-traditional options.

Be aware that there are multifarious oils, mediums, and thinners to use. Their use is based off of your own personal preference for drying and viscosity. At the end of this post I will provide links for additional reading, but the oils covered in this post will be straight forward and basic. 

What is a Medium and Why do we use them? 

A traditional painting medium is a mix of oil and thinner (such as turpenoid) that can do the following: extend your oil paint making it cover more area, modify the texture of the oil paint making it either thinner or thicker, and alter the paint sheen making it either high gloss or matte.

For me the easiest way to think of why we use a medium in oil paint is comparing it to watercolors. Water is the basic medium used to change the consistency of the watercolor paint just as oil is the basic medium used to change the consistency of oil paint. 

A Video about the Basics:

Before I get too much into the details about mediums, here is a short video from Web Art Academy that will help simply explain what I will be discussing in more detail.

Primary Oil Medium Binders

Binder is the substance that holds the pigments of the paint together. Adding additional binder to a paint will change the consistency of the paint. There are lots of oils to choose from, here is a list of the most basic:  

• Refined Linseed Oil: a thin oil, good for creating a low-viscosity medium, increases flow, slows drying time, has a lower tendency towards yellowing than cold pressed linseed oil, creates a good painting film when dry.
• The most traditionally used oil, but it does have a tendency to yellow. It is not recommended to use with white, or light, bright colors, or for final layers.  

• Stand Oil: a thick oil, good for creating a high-viscosity medium, increases flow, increases gloss, slows drying time even more than Linseed, is less yellowing than Linseed, creates a hard, enamel-like painting film when dry. 

• Walnut Oil: a thin oil, good for creating a low-viscosity medium, increases flow, slows drying time a little bit more than Linseed, non-yellowing, creates a slightly less-hard painting film than linseed oil.
• A favorite of Da Vinci and Durer, it was used through out the Renaissance, but was completely replaced by linseed oil during the Baroque due to expense and rotting issues. These are not longer problems with modern Walnut. 

• Poppy Oil: a very thin oil, good for creating a slick painting medium that holds paint strokes, increases flow, super slows drying time even more than Stand Oil, great for artists working wet-in-wet who need the paint to remain wet for days or weeks at a time.
• The favorite of Impressionists. It does create a very weak painting film and should not be used in layers under any other oil. 

• Safflower Oil: similar to Poppy is every way, but creates a slightly harder film and while still very slow drying, dries slightly faster than Poppy. 

• Cold Pressed Linseed Oil: Should be avoided due to its high tendency to yellow (this is from the Gamblin Site, I have read differing opinions on cold pressed, and the video above says it is the best, but I tend to trust Gamblin more).

To read more, I recommend the Encyclopedia of Painting Materials. 

Note: the painting film refers to the surface of the work after a layer of paint has dried. If the layer dries well and hard, the upper, wet layer, can then be wiped off and altered without damaging or lifting the lower layer.

Primary Thinners

Thinners are added to the oil binder in order to speed the natural drying time of a medium. Too much thinner, however, can leave the paint film weak and prone to cracking. Thinners are almost all toxic and should only be used in a well ventilated area. There are three primary categories of thinners: 

• Turpentine or Artist Turpenoid: These are generally almost completely odorless, does not leave a residue and evaporates quickly. I like Weber Artist Turpenoid. They are toxic.
• Mineral Spirits: Gamsol is the best, but more expensive mineral spirit. It is also to be  considered the safest of all turpenoid thinners as it is odorless, does not leave a residue and evaporates quickly. 

• Citrus Solvents: These are biodegradable options. I need to try one of these. I am interested in both Weber's Natural and Citra Solv. 

Basic Mixtures

You will want to use leaner mixtures at the beginning of a painting and fattier mixtures towards the end. This is a painting method called "fat over lean." Below are some basic mixtures. 

Leanest:

• Just Thinner

Leaner:

• 1 part Refined Linseed or Walnut Oil to 5 Parts Thinner

Lean: 

• 50/50 Refined Linseed or Walnut Oil/ Thinner
• 1 part Refined Linseed Oil or Walnut Oil, 1 part Damar Varnish, 5 parts Thinner 

Fatty: 

• 50/50 Stand Linseed Oil/ Thinner 
• 3 parts Oil to 2 Parts Thinner
• 1 part Oil (Linseed or Walnut), 1 part Damar Varnish, 3 parts Thinner

Fattiest: 

• Just Oil 

For more on mixtures read here and here.

Note: Damar Varnish is known to damage the painting as it ages. Most painting companies are moving away from it, but it is a very traditional medium additive. 

Which mixture should I use and When and How much? 

What medium to use, be it a mixture or not, takes time, experimentation, and practice. In my condensed post about mediums I recommend using a pre-mixed medium to start and then you can branch out from there.

When you should use different lean or fatty mediums is covered in my post about "fat over lean."

How much medium you should use, should always be the smallest amount. Always having more pigment to binder (oil) reduces the chance of yellowing, helps your colors sing, and insures the adhesion of consecutive layers.

I personally use a little plastic dropper to add medium onto my painting palette.

Or Take a Test:

Both Gamblin and Winsor and Newton have designed simple tests to help you pick which type of medium you should be using.

Click here for Gamblin and here for Winsor and Newton. 

Simple Options with  No Need to Create a Mix: 

These options take the guess work out of mediums. They are really fantastic and are widely used by artists, even traditional painters. They are usually toxic, but they are also non-yellowing.  

Galkyd: comes in several varieties, quickens or lengthens drying time depending on type, is toxic but not as toxic as Liquin.  

Liquin: comes in several varieties, quickens or lengthens drying time, is very toxic, use only in a well ventilated room.

Walnut Alkyd: is nontoxic, quickens drying time.

I covered these options in more depth here.

Can you Alter a No Need to Mix Option? 

You can alter your favorite galkyd or alkyd adding either thinner or oil. Adding thinner will quicken the drying time and oil will slow the drying time down. Warning! I do not believe you can add thinner or oil to liquin, but I am not 100% sure. I just can't find anything online about it.

I would recommend that rather than making large quantities of these altered medium mixtures, instead just add drops of either thinner or oil to the medium using a dropper on your palette.

Remember, however, that you still need to maintain the "fat over lean" principle.

Texturing Mediums:

All paint companies have some kind of medium that can be added to create texture. They are usually wax based and can really help you create that "van Gogh" look without using up a ton of paint. I will cover this more in another post.

What do I personally use? 

I am a solvent-free (or thinner-free) painter and I only use straight M Graham's walnut oil and walnut alkyd. I used to use a lot of thinner and loved it. I still love it, but making the switch and not having those toxins in my painting space has allowed me to concentrate better and paint for longer periods of time.

Not only is painting solvent-free safer for you, but it's also safer for pets and for little ones that may wonder into your space.

Below is a list of my personal mixtures. I use plastic drops to drop my mediums into a little pool on my glass palette. I then will dip my brush into this pool when needed.

Leanest: 5 drops of alkyd
Leaner: 4 alkyd / 1 drop oil
Lean: 3/2
Fatty: 2/3
Fattiest: 1/5 drops of oil

Wait, but do I have to use a Medium? 

NOPE! You want to just paint pure and free right out of the tube, do it! You'd still have to worry about the "fat over lean" principle, but more on that later.

Further Reading:

To read a lot more about Mediums click here and here.

For more about painting check out my main Tips and Techniques page.