How to Use Oil Painting Mediums|Solvents vs Oils vs Liquin

If you’re just starting out with oil painting, you’ve probably wondered: What exactly are oil painting mediums? Which ones do I really need?

Oil painting mediums like solvents, oils and alkyds are additives which you mix with your oil paint to change its consistency, drying time and the finish.. In this post, I’ll break down the main types I use, how they work, and when to use them. We’ll also look at the fat-over-lean principle, an essential concept that helps your paintings stay flexible and avoid cracking.

SOLVENTS

Solvents break downs oil paints, just like water in watercolours.

The most popular solvents are turpentine and mineral spirits. Turpentine is a traditional solvent while the odourless mineral spirits (OMS) are the modern alternatives. Sansodor by W&N and Gamsol by Gamblin are popular choices among OMS.

• TURPENTINE

  It’s a traditional choice for thinning paint, being used for centuries. It’s a strong solvent and evaporates quite fast. Its easily available and therefore most used by many artist.

  However, it has a very sharp smell, and is a toxic substance, should only be used in a proper ventilated area.

  I have experienced uneven drying sometimes in the past, and therefore switched to mineral spirits now a days.

  
  

  Turpentine has a ink like consistency, and drastically increases the flow of the brushstrokes. It’s a fast drying medium and ends with a matte finish.

• SANSODOR (OMS)

  Sansodor is less toxic and has a slower evaporation, giving a more even drying.

  Although it’s labelled odourless, that doesn’t mean it’s completely non-toxic. You should still avoid breathing it in directly and always work in a well-ventilated space.

  
  

  OMS has similar results to turpentine and almost identical consistency, drying time and finish.

  

I use solvents in the earlier stages, to create washes, sketches and underpainting. I can start the next layer even before they fully evaporate. Since the underpainting is already thinned it won’t affect the new layers much.

Solvents are also used to clean your brushes.

In the later stages of the painting, avoid them as they may disintegrate your earlier layers of paint.

Instead, use oils in the next stages.

OILS

There is some amount oil already in your paint tube. If you notice the small print on your tubes, it will mention which oils have been used inside. Most popular being linseed and safflower oil. But there are others as well like walnut or poppy seed oils.

• LINSEED OIL

  

  Linseed oil is the most widely used medium in oil painting. If you attended any oil painting workshops or classes, this what you will usually get recommended.

  It has much higher viscosity than solvents. It dries relatively faster than other oils but has a tendency to yellow overtime. Especially with whites and lighter colors.

Linseed oil increases the flow of the brushstrokes but not as much as solvents, but unlike solvents it doesn’t decrease the intensity of the paint. It has a moderate oil like consistency, is slow drying and ends with a glossy finish.

• SAFFLOWER OIL

  

  If you have issues with your paint yellowing, safflower oil could be the answer. It is paler in color and doesn’t yellow as much over time.

  
  

  Safflower Oil is a bit lighter in consistency as compared to linseed and hence slightly more fluid.

  Is has much slower drying time, if linseed oil takes a few days to touch dry, safflower oil can sometime even take a week. It ends with a similar glossy finish.

HOW MUCH OIL TO ADD?

As little as possible and only when needed. Just enough oil to get the consistency you need for the brush stroke.

Many workshops and courses will tell you to premix your paints at the start with about 10-20% or a couple of drops and use the mixture as you paint. This approach is ok if you are just starting out and need to familiarize with paints and medium.

But just keep in mind, each paint tube has different amounts of oil in it, so there is no fixed amount of medium that should go in every time.

My preferred way is to keep a small container with oils, and just touch the surface to pick up tiny amount and then see how it feels. If i need more, I will repeat the step.

LIQUIN

Liquin is an alkyd medium by W&N, Gamblin has its version called Galkyd. It speeds up the drying time significantly and give a glossy finish when dried.

Once mixed, it can get tacky after a couple of hours on the palette. I would therefore not recommend to mix all colors with Liquin at the start of your session. Only put a little bit of Liquin on the pallet (you can always add more later) and add it only at the moment of mixing your paint. Also, it has very strong odor and you should definitely avoid breathing the vapours.

Liquin has gel like consistency and similar results to oils when it comes to flow and glossy finish. But unlike oils it’s a very fast drying medium, often touch dry by the next day.

FAT OVER LEAN Principle

Fat over lean rule says that you should paint the leanest layer first, usually thinned with solvent. And each new layer should then contain a bit more oil than the one beneath it.

Following the fat-over-lean rule helps prevent your paintings from cracking over time. If you start with a fat layer and then add a lean one on top, the surface is likely to crack as the layers cure.

Lean layers dry faster, while fat layers—because of the extra oil—stay flexible longer. The movement underneath will cause the upper layer to split. To avoid this, the lower layers must always dry before the ones above.

My usual layers include:

1. A couple of coats of Gamblin oil ground,

2. Followed by an underpainting using paint with solvent.

3. Then the main layer with paint straight from the tube.

4. Another layer for any rework and adjustments with paint & oil

5. An optional glazing for any color corrections

6. And lastly a varnish, if the paint looks dull or uneven.

VARNISH

Lastly, Varnish. It’s not exactly a medium that you mix into the paint, but I wanted to cover it since it’s the final layer that can fix issues like dull or sunken areas caused by uneven drying.

I am using a retouching varnish over here by daler and Rowney. A retouching varnish is different than a permanent one, it is thin and porous, so its allows the paint layers to continue with their drying process with exposure to oxygen. While a permanent varnish will completely seal the top layer, and should only be applied once the painting is completely cured, which can take 6 months to a year.

BEFORE: This piece, for example, looks dull and matte on the right side.

AFTER: The left side has been coated with a varnish which brought back the richness, evened out the dark sunken areas and has given it a glossy finish.

BONUS TIP - SURFACE

If you are constantly struggling with achieving the flow you wish on your canvas, switching mediums is not the only solution. Many a times the surface on which you are paint makes a significant difference.

I have two canvas strips here, a cotton and a linen. And if you observe linen has much finer weave than cotton.

Now the smooth surface of linen allows the brush to glide more easily than the heavier textured cotton.

You can see the difference

1. Linen + Oil Ground , 2. Linen, 3. Cotton

Now you take it a step further, by using oil ground. I have this stretched linen canvas which has been coated with Gamblin’s oil ground. This makes the surface even more slick, the paint flows effortlessly and without addition of any medium.

CONCLUSION

I would say experiment for yourself.

There are many factors that affect how mediums behave, not just different brands of paint and medium, but also things like temperature and humidity in your area.

So don’t just follow someone else’s formula, not even mine. Make your own observations, try different ratios and combinations on a scrap canvas, and see what works for you.

I am simply sharing my experiences and what worked for me.

Hope these observations help you in some way.

YOUTUBE VIDEO: Oil Painting Mediums