Oil Painting Mediums

Cups of linseed oil and alkyd lined up at the Hillsborough Art Academy.

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Medium is a vehicle that's used to thin the paint and change the drying process. Different types of mediums impart different qualities, some dry paint quicker some make it stay wet longer.

All paint has some form of medium in it already. Oil binds paint pigment together, as the pigment is just a dry powder. It's simply color and then paint manufacturers add oil to it. Most paints these days are made with either safflower oil or linseed oil. I prefer linseed oil as a medium.

So with that in mind, let’s discuss several different types of mediums and why a painter might choose to use them. 

A display of how painters used to mix their own pigments with linseed oil. Credit: Old Holland Museum

Do I Need Medium to Oil Paint?

Generally speaking, paint is in it's finest condition the way it comes out of the tube. Quality paint manufacturers like Old Holland don't make a product designed to degrade with more medium. If more oil was required for the paint, they would put more oil in the paint. 

So the higher the grade paint the less oil you will have in it. If you open up a tube of paint and oil spills out of it, chances are you dealing with a lower grade material. So you can you can assess the quality of paint based on the amount of oil that's in the paint because paint pigments are a lot more expensive than oil binders.

When I paint, I add extra linseed oil to the paint to thin it. This also slows down the drying process a little, but the big thing is the thinning of the paint.

Rule of Thumb

The general rule of thumb when you add medium to a painting is you don't want to thin the paint unless it's your intent. You don't want to add medium to a point where the paint is no longer opaque or solid. Rather, you want a stable paint film that you can easily move about on your canvas.

This means that you never want more than 50% of your mixture to be oil. Ideally, you will have much less than half, just a little bit of oil, because the paint as it comes out of the tube is in its most pristine condition.

You should use a medium only if necessary. If you are using quality paints medium is not necessary most of the time. But if you require paint to dry quickly, slowly, or be a bit thinner, medium is a good choice.

Medium can thin down opaque paint or increase the fluidity of glaze.

Alkyd Medium

In general,  people want their paint to dry faster and for that, we use an alkyd. Alkyd is a chemical that has some solvent in it. One recognizable solvent is turpentine, which breaks down binders in the paint, drying them at a faster rate. 

Alkyd will dry a painting overnight unless the paint is very thick. Generally, it will dry paintings within 24 hours that you can work layer on top of layer for several days in a row. This is beneficial for quick turnarounds in paintings and techniques like speed painting where it is necessary to paint in thin layers.

Alkyd Used As An Isolating Layer

Alkyd medium can function as an isolating layer called “sealing a painting”. This simply is the process of locking completed layers of paint in place so that glaze or additional paint can be put on top without removing any paint.


Here at Evolve, we always mix alkyd into linseed oil. And the reason is that alkyd by itself will start to dry up the paint very quickly. So if you sit down to work in a three-hour window, the paint will begin to stiffen up. While there are times this may be desirable, often mixing linseed oil into alkyd produces the most workable paint drying time.

Linseed oil being combined with pure paint pigment. Credit: Instructables.com.

Painting with Linseed Oil 

Linseed oil is a standard and traditional medium used to make most paints. It will simply thin the paint and make it stay wet a little bit longer.

When mixed with paint it slows down the drying process so that over a long day of working your paint will remain pliable and not begin to dry or become sticky. However, it will often take longer than 24 hours to dry if used alone.

And so, I mix linseed oil into alkyd, generally in four-part linseed oil to one part alkyd ratio. And what that does is give me a medium that stays workable for several hours, but will still dry overnight. After four or so hours the paint will begin to stiffen slightly, but it is still very workable and pliable and will be dry for work the next day.

A paint palette preserved for many days with clove oil. Credit: Daniel Corey

Clove Oil in Painting 

On the other end of the spectrum, if you want the paint to stay wet longer, you would use clove oil. Clove oil is not technically an artist material, it’s actually an essential oil and is available at certain markets or pharmacies. Clove oil is usually used for two things: cooking and toothaches.

However, if you take clove oil and add it to your paint it will keep your painting wet for days. Only a few drops are necessary, and you do not need to add any other medium to your paint. 

Clove vs Linseed Oil

When using linseed oil, it will keep the paint wet for several hours, but clove oil can extend the paint drying for four or more days with only a few drops. Again it is important to only use a small amount, and when mixed with certain colors like cadmium red, the paint will stay wet for much, much longer. These are important things to keep in mind before you use clove oil.

All in all, clove oil can be a very helpful tool for artists, particularly when working on large pieces or artists who may need to extend their palette to stay wet for several days.

Kevin used medium to speed drying and increase opacity in this painting.

Conclusion

Different mediums are used for different purposes. This is crucial when deciding the medium you wish to add to your paint. If your intent is to extend drying time, then consider linseed oil or clove oil. But if you wish to have your paint dry very quickly a combination of linseed oil and alkyd or pure alkyd will be helpful.

Your intent is always important to consider as you choose a medium, and keep in mind that paint in its purest form, out of the tube, is often all you need.

Note: It is important to note that alkyd and especially clove oil are not safe for animals. It is important to keep these mediums away from your pets and use in a well-ventilated room. As always, try to keep your pets out of any artist materials.

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(4) comments

Linda

Thank you Kevin. That was very informative and great to know. It takes some of the mystery out of what mediums a painter should use and when to use it. I especially liked the linseed oil and alkyd combination!

Thanks for sharing!
Linda

Reply
    Piper Talladay

    Hi Linda!

    We’re glad this was helpful! Hopefully this gives you great success as you work!

    Piper

    Reply

I love using Old Holland paint it is a very different experience the feel of the paint is fantastic, The problem is how fast it dries, I have found it very waist full, and so very expensive. I bought walnut oil and that has solved the problem. I store it in a mastersons stay wet palette which is air tight. My paint can stay wet for days depending on how much I use. I would like your view on this.

Reply
    Piper Talladay

    Hi Antoinette!

    Old Holland can dry quite quickly, which can be very helpful at times and frustrating at others! Here at Evolve, we use linseed oil with a combination of Alkyd to create the perfect drying time for our paint. This allows the painting to be worked into for about 6 hours, but dry for work the next day.

    Quality walnut oil can be quite a bit more expensive than linseed oil and dries slower. This can be helpful if you want your paint to stay wet but causes issues if you wish to work the next day, or even in the next two days. The viscosity of walnut oil is a bit different as well, which causes a different texture to the paint. If the texture of the walnut oil is causing the paint to be too difficult to work with, I would recommend trying clove oil, a less expensive product that also slows the drying time significantly!

    Reply
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