About Mediums (Learn to Oil Paint pt. 3)

If you aren’t loving the texture straight out of the tube, you can mix in a little bit of oil paint mediums such as: Gamsol (thinner), linseed oil (medium), or Liquin (medium). Each of these behave a little bit differently…

Me, previous post.

Welcome to the Mediums section in my series of how to start oil painting even if you’ve never touched a paintbrush!

This post assumes you already purchased your materials – but feel free to read ahead if you haven’t quite decided what oil paint mediums you want to buy!

Please be aware that as an affiliate, I may receive a small commission on purchases made through my links at no extra cost to you; I appreciate the support!!

Oil Paint Mediums – Gamsol (Thinner)

Gamsol, an oil paint medium (thinner)

Gamblin’s Gamsol is an odorless paint thinner. This means it breaks down the paint and the oil – thus thinning it out. It is useful for rinsing out excess pigment from your brush if you are switching colors, cleaning up your brushes when you are finished, as well as diluting your paint. (Note that even though it is “odorless,” it still has fumes and your area should be well ventilated.)

When you use Gamsol to dilute your paint, a few things happen:

  • the paint becomes more runny
  • it becomes less opaque (more transparent)
  • the paint will dry much faster
  • it will have more of a matte finish

These effects can be really useful! A lot of people like to add Gamsol to their paint for their underpainting, which is basically a map on the canvas of what you want to paint! Because of the thinner, this layer will dry relatively quickly and then you can start your painting easily.

To use it for cleaning your brushes…

…pour some into a jar and gently swirl the dirty brush around. Pull it out and wipe on a paper towel or rag, and repeat. Once most of the pigment is gone, you can switch colors, or, to clean them, you can do a second jar with clean Gamsol to rinse the rest of the way.

It is important to note that leaving the brushes sitting with Gamsol remaining in them will damage the brushes. (Yes, I learned that the hard way, lol.) Additionally, my favorite brush makers, Rosemary & Co., suggest not to use mineral spirits AT ALL. I plan to write more on this, but until then, they have a blog post dedicated entirely to caring for your oil painting brushes and I highly recommend reading through it.

When you are done with a painting session…

Rinse your brush with clean linseed oil OR very gently wash your brush with cool water and dish soap. If you go with linseed oil, you can just wrap up your brushes (Costco’s plastic wrap is bomb) and place them in the freezer to keep them from drying out as quickly. If you choose to wash them, make sure to let them dry horizontally, not with the brush end up. If the brush is drying pointed up, the moisture can damage your ferrule (the metal part where everything is joined together).

Whatever you decide to do, *please don’t* leave your brushes drying out with Gamsol in them!

Read what my brush makers say about keeping your brushes performing their best here.

Oil Paint Mediums – Linseed Oil (Medium)

Linseed oil, an oil paint medium

This is the traditional medium that is used to mix in to the oil paints. It extends the dry time of your paint considerably – which is helpful so that you can keep manipulating it to get things just where you want them, even when you are painting over a longer period of time. You should have adequate ventilation while oil painting.


In terms of paint texture, adding linseed oil to your pigment makes the paint more fluid and glossy. It will have more of a flow to it than the paint does straight out of the tube.

Dry Time

Depending on how thick you like to paint, how many layers you add, etc., oil paintings that use linseed oil for their medium can take months to fully dry. You should NOT try to varnish your painting before it is fully touch-dry (and even then, maybe wait a little longer).

When I finished ‘Lotus Temple,’ I waited over three months to let it dry. Since it was only my second “real” finished painting, I didn’t have the experience to realize that it was not ready for varnishing. I thought it was “dry enough” so I began to varnish it – and it didn’t go too great. Luckily, I stopped before I did the whole thing because it began to smear the paint slightly. It was taking away the nice crisp edges, and I didn’t want to ruin my whole painting. Still, to this day, that painting isn’t a solid “dry” because I varnished it too early. It has been A YEAR y’all.

Please, learn from my mistake and don’t varnish too early. 🖤

Oil Paint Mediums – Liquin (Medium)

Lquin Original, an oil paint medium

Now we get to Liquin!

I love Liquin. Honestly. It is fantastic. I should have put a halo around it’s picture over there. But I digress.

The point of this medium is to actually help the oil paint dry faster. We aren’t talking as fast as acrylic paint – but you won’t be stuck waiting months for your painting to be dry, either. The smell is strong with this one; please open your window and give yourself plenty of fresh air.


Like linseed oil, Liquin makes your paint more fluid, but even more glossy. It has kind of a funny texture, not quite liquid, not quite solid. But once you start working it into your paint (I use a palette knife) it dissipates into the pigment and you are left with a lovely paint texture.

Dry Time

Liquin helps your paint dry a lot faster than linseed oil. Your painting may be touch-dry in a few days. Definitely still be totally sure it is fully touch-dry before throwing varnish on, but you will not be waiting nearly as long! This has pros and cons. If you are wanting to get something painted, dried, and varnished quickly (this is how I do it so that paintings don’t take a year to be ready), liquin is great; if you need your paint to stay malleable for a longer period of time (have to take breaks/paint inconsistently), you might prefer linseed oil.

“Fat Over Lean” – um, what??

Fat over Lean oil paint mediums infographic; shows how oilier paint should be placed on top of the less oily paint.

You’ve probably watched some youtube videos, or casually (or obsessively…) read some articles, and have heard the phrase “fat over lean” while trying to figure out the mysteries of oil painting. Maybe it makes perfect sense to you. For me, it didn’t.

In simple terms, this rule (are there really any “rules” in art?) means that you should always work with the least amount of added oil (or medium) first, and then add more and more as you build up the painting.

Why this is Important

This is important because if you try to put “leaner” paint on top of “fatter” paint doesn’t really work very well. Lean paint on top of fat results in uneven drying and could crack. You will also have a harder time getting the lean paint to stick on top of the fatter paint properly. It is definitely worth experimenting so that you can feel what this means, but my infographic should help!

After the Oil Paint Mediums – Varnish

gamvar gloss, oil painting varnish

Varnishing comes once the paint is totally touch dry. You should be able to touch the thickest area and it shouldn’t budge.

There are a few different finishes of varnish, so you can get a really nice pop and definition on your painting, with whatever finish you are looking for!

I really enjoy Gamblin Gamvar Varnish! You don’t need a lot, and it is important to let each layer dry before adding another.

Something to be aware of: varnish is STICKY.

Place paper or something on your work surface. I have discovered that if I accidentally get some on my hands, washing with soap and water, then using lotion, then washing with soap again takes it right off! I am assuming this is because of the oils in the lotion. All I know it is works!

I also suggest using a separate brush from your painting brushes, to keep them all working their best. Once again, be sure to open your window, turn on a fan (that is, if you don’t have hairy dogs whose fur will get blown into your varnish…), or open the door so that you have adequate ventilation.

Now that you know more about how these oil painting mediums work, play around with them! This post has gotten a little wordy, so I’ll wrap it up here. Stay tuned for more in the journey of how to start oil painting!!

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