Art et peinture

Mediums Are the Key to Water-mixable Oil Paints

Most water-mixable oil painters use mediums to increase the flow of their paints instead of water and only use water to clean up – I like to think of water-mixable oils as water-washable oils. There are also mediums for extending, thickening, and increasing or decreasing the drying times of the paint.

At Jackson’s, there are six water-mixable oil (WMO) brands that each make a selection of mediums to modify your paints in various ways. The most often used medium is ‘painting medium’ which extends the paint and allows it to flow more smoothly off the brush. There are paste or gel mediums that allow you to thicken the paint or to increase transparency without losing body. There are mediums formulated for glazing techniques and mediums to accelerate drying. Water-mixable linseed or safflower oils can be added to paint to increase flow and slow drying, or they can be used as ingredients when making your own water-mixable mediums. WMO mediums come in fairly small bottles or tubes, but it takes very little to get the paint to flow smoothly. A general rule in all oil painting is to only use as much medium as you need to get the modification you want – excess medium could make the paint too oily and can cause drying problems or wrinkling. For this article, I have mixed a wide variety of water-mixable oil mediums with paint to find out the characteristics of each one and how they are best used.


Water-mixable oils and mediums are referred to by a few names but they all mean the same thing: watermixable, water-soluble, water-miscible, water-reducible, WMO, and aqua oils. Below is a list of all water-mixable oil mediums currently available at Jackson’s, by brand:

Winsor & Newton Artisan

  • Painting Medium
  • Fast Drying Medium
  • Impasto Medium
  • Thinner
  • Linseed Oil
  • Safflower Oil


Holbein Duo Aqua Oil

  • Painting Oil Medium
  • Quick Drying Liquid
  • Quick Drying Medium (paste) in Gloss and Matt
  • Linseed Oil
  • Linseed Stand Oil


Talens Cobra

  • Painting Medium
  • Quick Drying Medium
  • Paste Medium
  • Glazing Medium


Grumbacher Max


Daniel Smith Water Soluble Oil

  • Painting Medium
  • Fast Drying Medium
  • Transparent Blender
  • Linseed Oil
  • Fast drying Linseed Oil
  • Safflower Oil



  • Medium W
  • Medium W Gel
    These can be mixed with conventional oil to make it water-mixable. Can also be used as a glazing medium and slow drying medium for WMOs.


M. Graham Walnut Alkyd Oil Medium

This is not a water-mixable oil medium. I’ve included M. Graham because it is a favourite of WMO painters and it is so fluid that you use very little which then doesn’t interfere with the water wash-ability at all.

Note: I have recently had Gamblin’s Solvent-free Gel recommended as a good medium for WMO, even though, like the M. Graham, it is not water-mixable itself. Because you use so little the water-washability is not affected. Since it was after these tests were done, it is not included in them, but I wanted to at least mention it.

Characteristics of the Different Makes of Water Mixable Oil Mediums

WMO mediums impasto chart closeup

To find out more about the mediums I grouped them into four types based on the modification you might want to achieve with your paint:
1. Painting Mediums – to increase flow, make more fluid
2. Impasto Medium – to thicken the paint or to increase transparency and extend the paint while not losing too much body
3. Fast Dry Mediums – to speed up drying
4. Oils and Glaze Mediums – to slow down drying, extend paint, increase transparency, increase fat for final layers, for glazing

Testing Method

I made a chart for each of the four groups of mediums. Many water-mixable oil painters like to use M. Graham Walnut Oil Alkyd Medium, which is not a water-mixable medium, but since you use so very little it does not interfere with the water-washability at all. So I added it to all the tests. I also added mixing with just water and neat paint for a baseline comparison.

I mixed the mediums with two brands of paint that have quite different characteristics: Jackson’s Aqua Oil because it is sensitive to water-seizing, it is buttery-stiff so needs a medium to make it flow more and it dries nearly matt with no tack; and Daniel Smith Water Soluble Oil because it is not very sensitive to water-seizing, is buttery out of the tube so only needs a little help to flow and dries glossy and tacky. All tests except the impasto are 10 parts paint to 1 part medium, the impasto mediums were mixed in a 50-50 ratio. They were all mixed on a palette and then applied to the chart panel. The application was in three thicknesses: a thick patch with a palette knife, then a stripe with a loaded brush, and a stripe with a drier brush for a thinner layer. The drying times listed are for the thinnest layer being touch-dry, unless I state otherwise. The colour is Ultramarine Blue. The panel is a Jackson’s Premium Cotton Canvas Art Board.

The General Findings

Because it takes so little medium to modify the paint, you don’t lose the characteristics of the paint. The paint to which you add the medium will be a main factor in the resulting mix. If the paint is fast-drying or matt or fluid – those characteristics will remain and have a big effect on the results. So the same medium mixed with different paints will behave differently.

All the brands of mediums mix fine with other brands of paint. I mixed and matched brands in my earlier tests and this remained true. But some make particularly good pairings, like Cobra Quick Dry Medium with Jackson’s Aqua Oil, Artisan Painting Medium with Daniel Smith, and M. Graham Walnut Oil Alkyd with Jackson’s Aqua Oil.

Water-mixable oil mediums are compatible with conventional oils but will not make them water-mixable because you don’t use nearly enough. Only the Schmincke Medium W, used in a ‘one part medium to two parts oil paint’ ratio, will allow conventional oil paint to become water-washable.

I checked odour because some artists choose to use water-mixable oils because they are sensitive to the odours associated with traditional oil painting. I found that some of the water-mixable mediums have a strong chemical smell while some have a mild linseed oil smell. You will see those results in each section.

Painting Mediums

Painting Medium

These are extenders that allow the paint to flow more.

  • Artisan Painting Medium
  • Holbein Painting Medium
  • Cobra Painting Medium
  • Daniel Smith Painting Medium
  • M. Graham Walnut Oil Alkyd

Adding Painting Medium to the paint helped with its washability. All brushes, even M. Graham (not water-soluble), rinsed out well without soap except Artisan which needed a bit of soap.


Artisan – fairly strong chemical smell like formaldehyde
Holbein – slight chemical smell and linseed smell
Cobra – mostly a light linseed oil smell
Daniel Smith – mostly a light linseed oil smell
M Graham – mostly a light oil smell

water-mixable oil mediums

When I washed the pipettes that I had used – the four that I used with the water-mixable mediums turned milky as they became emulsions with the water, and as expected, the M Graham did not as it’s not water-mixable. It just reminded me that these are indeed different, so I thought I’d share it.

Water-mixable Painting Mediums

Painting Mediums left to right: Artisan Painting Medium, Holbein Painting Medium, Cobra Painting Medium, Daniel Smith Painting Medium, Graham Walnut Oil Alkyd. An odd finding was that the Holbein Painting Medium is very fluid or has no surface tension – the one drop spread very far when it was dropped onto the palette while the other four brands stayed as drops. Though you will see in the test results that it did not make the paint more fluid, when mixed with paint it was stickier than the others.

Painting Mediums mixed with Daniel Smith
  • All five brands mixed in easily, the paint sort of melted into them.
  • Artisan and Cobra had the smoothest flow.
  • Holbein was a bit sticky, a little harder to brush smoothly.
  • As expected, water was harder to mix in than the mediums were, but flowed fine (and dried more matt).
  • As expected, neat paint flowed the least as it was still thick.
Painting Mediums mixed with Jackson’s Aqua
  • They all created a lovely smooth flowing mixture.
  • M. Graham flowed the most.
  • Holbein flowed least of the five with both paints, but it wasn’t bad. It was just surprising since it is the most fluid. Maybe it is more like a thinner than an extender.
  • The 1 part medium to 10 parts oil paint (1:10) significantly increased the transparency of the Aqua paint.

Jackson’s Aqua oil mixed with left to right: M. Graham Alkyd, water, neat paint.

The Gloss of the Painting Mediums

Daniel Smith water-mixable paints are glossy on their own. All the painting mediums except for Holbein, when mixed with Daniel Smith made the paint even glossier.
Jackson’s Aqua water-mixable paints are satin-matt on their own. Daniel Smith and M. Graham mediums, when mixed with Jackson’s Aqua paint, made the paint glossier. Artisan and Cobra made it slightly glossier. Holbein didn’t change the natural sheen of the paint.

Drying Times

Time until the thinnest paint layer was touch dry

  • Painting medium mixed with Daniel Smith.
    Cobra, Daniel Smith and M. Graham 1-2 days.
    Artisan, Holbein (also the water and neat sample) 3-4 days.
  • Painting medium mixed with Jackson’s Aqua Oil.
    The same drying times as Daniel Smith except they were all one day faster.

Impasto Mediums

Impasto Mediums

  • Holbein Quick Drying Medium (paste)
  • Cobra Paste
  • Daniel Smith Transparent Blender
  • Medium W Gel
impasto medium

left: Holbein Quick Drying Medium (paste). right: Medium W Gel

impasto mediums

left: Daniel Smith Blending Medium. right: Cobra Paste

Odour and texture
  • Daniel Smith transparent blender = low smell
  • Cobra paste = low smell. The thickest and firmest, had the highest peaks. Lovely, jewel-like and very smooth. The only one that was as thick as paint.
  • Duo quick dry medium (paste) gloss = medium smell. Sticky like stringy honey.
  • Schmincke Medium W gel = medium smell, very smooth, melts into paint. It is thixotropic, meaning it becomes a more thin consistency when you move it about and brush it, and then it thickens up again when it sits still.

Four impasto mediums plus neat paint. Mixed 50-50. This image is right after painting, while it was still wet.

Same chart as above – after 6 weeks of drying. As always, click on the image to zoom in.

Although Holbein Quick Drying medium is a paste that comes in a tube, it is quite soft and doesn’t give any impasto texture. But if you want to add a fast-drying quality without losing too much body, this might be good for you.

Brush cleaning after using the impasto mediums

Info for both brush rinsing between colours in only water and final brush washing with Jackson’s Marseille soap.

All four impasto mediums when mixed with Daniel Smith paint made the brush harder to rinse than with just neat paint, but washing was rated good.
All four impasto mediums mixed with Jackson’s Aqua paint were easy to rinse out and super easy to wash.

Impasto Drying Times

A thin layer of neat paint took 3 days to dry in both paints.

  • Holbein Quick Dry (paste) sped up the drying time of the paint by a day.
  • Schmincke Medium W Gel didn’t change the drying time of the paint.
  • Daniel Smith Transparent Blender didn’t change the drying time of the paint.
  • Cobra Paste slowed down the drying time of the paint.

Fast Drying Mediums

Fast Dry Mediums

  • Artisan Fast Drying Medium
  • Artisan Thinner
  • Holbein Quick Drying Liquid
  • Cobra Quick Drying Medium
  • Max Quick Dry Medium
  • Daniel Smith Fast Drying Medium
  • Graham Walnut Oil Alkyd
  • Artisan Fast Drying: strong formaldehyde
  • Artisan Thinner: spirits, slightly citrus
  • Duo Quick Drying Liquid: slight chemical
  • Cobra Quick Drying: linseed oil smell
  • Max Quick Dry: moderate smell like curry powder
  • Daniel Smith Fast Drying: linseed oil smell
  • M. Graham Walnut Alkyd: mild oil smell
Fast-drying mediums mixed with Daniel Smith

Holbein mixture was sticky like thick honey not flowing.
Thinner is oily not like a solvent.
All had good flow except Artisan Fast-Drying medium and Duo Quick dry liquid. Which were thick and sticky.

Brush Washing

Artisan Fast Drying Medium, Artisan Thinner, Holbein Duo Quick Drying Liquid, Daniel Smith Fast Drying Medium, M. Graham Walnut Oil Alkyd – brush rinsing was moderate, washing was easy.
Cobra and Max – brush rinsing was poor, washing was easy.

Drying times

All brush marks were dry in less than 24 hours except for the Thinner.
With Holbein Duo Quick Dry – a thick layer was dry in one day.
All the rest a thick layer was not dry in one day.

Fast-drying mediums mixed with Jacksons Aqua
  • Artisan Thinner changes the colour, it is lighter temporarily. It mixes in easily, is not thin like a solvent.
  • Cobra and Max and Artisan Thinner flow beautifully.
  • Cobra has the most flow it is lovely
  • Max flows but has more body
  • Cobra Quick Dry Medium and Jackson’s melt together particularly well.
  • Artisan Fast-Drying didn’t flow much.
  • Daniel Smith flowed but was a bit thicker like Max.
  • Graham was great with both paints.
Brush Washing

For rinsing, all rated ‘good’, except Duo and Cobra rated ‘moderate’.
All 7 washed ‘easy’.

Drying Time

All thin and all thick layers were dry in one day.

Water mixable oil thinner

Winsor and Newton Thinner is the droplet in the middle. It is not thin like a solvent. It is oily and really nice.

  • It makes sense that Grumbacher Max would make a Quick-dry Medium as their paint is the slowest drying water-mixable oil. Max has two important notes on the bottle: 1. Apply in thin layers and allow to dry between coats. 2. Do not pre-mix medium with water prior to blending with paint.
  • I liked the Artisan Thinner a lot. Because of the name, I thought it would act like turpentine and be a solvent that dried quickly, but it was oily with body and didn’t dry quickly. I put it in this group for the tests but I now consider it to be a painting medium, to be added for flow.
  • Holbein needs a good shake until it forms a cloudy emulsion. That means it contains water, but so does the Cobra which doesn’t need shaking.

Slow Drying and Glazing Mediums

Glaze Mediums

  • Holbein Linseed Oil
  • Cobra Glazing Medium
  • Daniel Smith Fast Drying Linseed Oil
  • Medium W
  • M Graham Alkyd

They all had a similar viscosity.
They all melted into the oil paint, with Cobra and M. Graham doing especially well. Much easier to mix into the paint than water was.
Holbein Duo Linseed Oil was the least flowing off the brush.

Holbein Duo Linseed

Nice oil smell
Mixed with Daniel Smith – brush rinsing was poor, washing was easy.
Mixed with Jackson’s Aqua – brush rinsing was good, washing was easy.

Cobra Glazing Medium

Mild odour
Mixed with Daniel Smith – brush rinsing was poor, washing was easy
Mixed with Jackson’s Aqua – brush rinsing was very good, washing was easy

Daniel Smith modified linseed oil

Linseed oil smell
Mixed with Daniel Smith – brush rinsing was poor, washing was easy
Mixed with Jackson’s Aqua – brush rinsing was poor, washing was easy

Medium W

Mild odour
Mixed with Daniel Smith – brush rinsing was good, washing was easy.
Mixed with Jackson’s Aqua – brush rinsing was good, washing was easy.

M Graham Alkyd

(remember, this one is not water-mixable)
Linseed oil smell
Mixed with Daniel Smith – rinsing was very poor, washing was easy
Mixed with Jacksons Aqua – rinsing was very poor, washing was easy

Drying times:

A very thin dry-brush layer was dry in:
1 day: Medium W mixed with Daniel Smith and M. Graham mixed with both paints
2 days: Medium W mixed with Jackson’s, Duo mixed with Daniel Smith, Daniel Smith oil mixed with both paints.
3 days: everything else.

glaze mediums and oil water mixable oil mediums

The Fat-Over-Lean Principle

If you paint in layers, letting each layer dry to the touch, then you will want to stick to the fat-over-lean rule to create a stable painting. You would start with the leanest medium mixture in the lower layers and end with the oiliest for the top layer. You can make a water-mixable medium leaner by adding water to it. Cobra Painting Medium is half water already. Cobra Glazing medium in the same as their Painting Medium but with no water. So by starting with a mixture of a lean medium and water, then moving to just the lean medium and ending with the oily medium with no water, you can control how much oil is in each paint layer and be sure that each layer is more flexible than the layer underneath. If on the other hand, you are painting your whole painting in one sitting or in a couple of days where no layer dries while you are painting, then you don’t need to worry about fat-over-lean because you do not have separate layers.

More Water Mixable Oil Painting Articles on the Blog

References and to read more

Cobra have created an excellent series of eight videos on painting with water-mixable oils and using mediums.

Modern Paints Uncovered The article is The Performance and Properties of Artisan Water Mixable Oil Colour Compared with Other Oil-Based Paints by Winsor & Newton (pp 53-57).

Physical Properties of Traditional and Water-Miscible Oil Paints as Assessed By Single-Sided Nmr

Solving the Solvents

Water sensitivity of modern oil paint films – Tate

Links to the materials at Jackson’s

Water-mixable Oil Paints

Water-mixable Oil Mediums

Schmincke Medium W

M. Graham Walnut Alkyd Medium

Retouching Varnish

Final Picture Varnish

Jackson’s Akoya Brushes

Masters Brush Cleaner

Chelsea Classical Lavender Soap

Jackson’s Marseille Soap

Brush Cleaning Egg

Jackson’s Premium Cotton Canvas Art Boards


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