In painting, "medium" refers to both the type of paint and an amendment to alter the properties of paint. A painter can mix a medium with solvents, wax, pigments and other substances in order to make paint and control consistency. Often the term "paint medium" refers to the fluid that carries pigments, but this is more properly called called a "vehicle," which is typically composed of a solid binder and a solvent. An example of an artist paint vehicle is watercolor, where gum arabic is the binder and water the solvent.

Oil paint is a slow-drying paint consisting of pigment particles suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent, such as turpentine or mineral spirits (white spirits), or varnish may be added to increase the glossiness of the dried film. In this section, you will find oil painting mediums or additives (or as we prefer to call them "amendments") made by Natural Pigments. These amendments are designed to alter the consistency of oil paint in novel ways, different from the varnishes that were introduced into common use during the 19th century.

Painting mediums can change the handling properties of paint, such as flow out and leveling; increase or decrease tackiness and drag; hasten or retard drying time, increase or decrease gloss, increase transparency, or other characteristics.

Painting Medium Suggested Uses
Paint MediumGlazingImpastoOiling Out
Impasto Medium Yes Best No
Velázquez Medium Yes Best No
Venetian Medium Best Yes Yes
Oleogel Best Yes Best
Oleoresgel Best Yes Best
Wilson's Medium Best No Yes
Italian Varnish Best No No
Balsam Essential Oil Medium Best No No

Paste Mediums

Rublev Colours Oil Painting Paste Mediums

Calcite is a naturally occurring calcium carbonate (CaCO3) mineral chiefly found in rocks, such as chalk, limestone and marble. These rocks are the main sources for the pigment. Its whiteness, softness and fine-grained nature makes it an ideal white pigment, being both abundant and easily processed. Chalk is relatively transparent in most paint media and is therefore often used as an extender of other pigments and employed with animal glue as a ground for painting.

History of Calcite in Art

Calcium carbonate in various forms has a long history in art. It has been recognized, for example, in Greek and Roman art. Its use in art since that time has been both persistent and widespread. In northern Europe, from medieval times chalk was employed with animal glue for making the ground or preparation layer of paintings. Sometimes later lead white was mixed with the chalk to make it denser and whiter. Chalk was used with animal glue or with other aqueous binders as a white pigment.

Calcite has been used in oil painting, being added to colors, especially flake white, by such artists as Velázquez and Rembrandt. The transparency of chalk was desirable in some Dutch tonal landscapes of the seventeenth century.

Uses of Calcite in Paint

Calcium carbonate is commonly used in combination with other pigments in oil paint because of its low refractive index and hence poor hiding power. Linseed oil and chalk have long been used together, however, in the preparation of putty. The transparency of chalk in oil makes it ideal for adding bulk to oil colors or to affect the consistency (rheology) of paint.

Calcium carbonate is often used as an extender pigment to reduce the cost of paint. Its alternative names, such as chalk and whiting, are used in many formulations. An important use of calcium carbonate is in mixtures with titanium dioxide pigment to act as a spacer, keeping the titanium white particles spread apart, and ensuring better efficiency in scattering light and increasing opacity. Calcium carbonate is often used to vary the gloss of powder coating materials, depending on the particle size used.

Variations of Calcite and their Effects on Paint

Calcium carbonate derived from different mineral sources behave differently in paint. The material can be ground from limestone, a sedimentary rock formed in sea beads or alluvial deposits; or marble, which is limestone that has undergone heat and pressure below the earth's crust; or chalk, a light, low structure material normally associated with the sedimentary deposition of the shells of such minute marine organisms as foraminifera, coccoliths and rhabdoliths. The particle structure and chemical behavior of these variations of calcite all differ slightly.

The particle size and shape of calcite in regards to the behavior and performance of paint are important for several reasons. One is the viscosity of the paint, which is related to the volume occupied by the dispersed solids within the paint vehicle. In the case of particles that are not spherical, the "spherical equivalent" volume may be the maximum volume inscribed by the rotation of a particle. Because of this, a non-spherical particle may behave as if it occupies much more volume than it does.

Another consideration of the influence of particle size and shape on the behavior of paint is the surface area of the particle. The amount of paint binder required by a pigment to form a paste paint is called its oil absorption number. The greater the surface area of the particle, the more binder it demands to make into a paste or flowing paint. Synthetic (precipitated) calcium carbonate that consists of 0.05 micron needle-shaped particles has more surface area than the particles of ground limestone of the same size, which have simple structures resembling rhomboidal crystals. Because of the complex surface of the precipitated calcium carbonate, it will tend to scatter more light and consequently appear more opaque than the ground limestone particles. However, it is likely that this precipitated calcium carbonate will consume considerably more binder than the ground limestone.

Selecting the right type of calcite, taking into consideration particle size and shape, brightness, chemical constituents, and surface treatment are important factors when it comes to making paint or oil painting mediums.


Rublev Colours® Impasto Medium

Rublev Colours Impasto Medium: Oil Painting Medium
Impasto Medium is a calcite-rich oil painting medium.

Impasto Medium is an oil painting medium of finely ground calcite, silica and bentonite in bodied linseed oil. Use it to extend paint without altering the consistency, making oil colors 'short' and buttery for impastos. Stiffer than Velázquez Medium, this putty-like medium makes colors slightly transparent while allowing you to build impasted, thick applications of paint. When added to oil paint, Impasto Medium does not alter its color temperature. It can be thinned with solvent or oil. Depending upon the proportion added to paint, Impasto Medium does not affect the drying time significantly.

Impasto Medium does not contain stearates, solvents, driers or natural or synthetic resins, so it is safe to add to oil paint without the worry of cracking or delaminating.

Impasto Medium slightly increases the transparency of colors while maintaining the buttery consistency. It allows you to build impasto or thick paint with ease. When added to oil paint, brushstrokes hold their form without slumping or leveling. In the picture below, when added to green earth artist oil (bottom center), the mixture of Impasto Medium (bottom left) extends the color and its consistency, while the mixture with Velázquez Medium (bottom right) gives the paint a long, ropy consistency.


Rublev Colours® Velázquez Medium

Rublev Colours Velázquez Medium: Oil Painting Medium
Velázquez Medium is a pure calcite oil painting medium.

Velázquez Medium is an oil painting medium of finely ground calcite in bodied linseed oil. Use it to extend paint and alter its consistency, making oil colors 'long'* for finer detail and impastos. Softer than Impasto Medium, this flowing paste makes colors slightly transparent while allowing you to build impasted, thick applications of paint. When added to oil paint it does not alter the color temperature. It can be thinned with solvent or oil. Depending upon the proportion added to paint, it does not affect the drying time significantly.

Velázquez Medium does not contain stearates, solvents, driers or natural or synthetic resins, so it is safe to add to oil paint without the worry of cracking or delaminating.

*Long refers to the consistency of paint that displays tall peaks when a palette knife is pressed to its surface and lifted. Long paint is also described as being a "ropy" and refers to a stringy quality, like that of honey. Paint that behaves in this way is said to have long rheology. Short rheology refers to paint that exhibits a more buttery consistency, typical of most commercial oil paint. Rheology is the study of how substances flow, such as liquids and soft solids that flow rather than deform elastically.

The soft white paste has little affect on color, making them less opaque and slightly less saturated. Use it to build thick applications of paint.

Velázquez Medium slightly increases the transparency of colors while introducing flowout and leveling. These properties allow you to create fine detail in impasto or thick paint with ease. Although the paint becomes long when Velázquez Medium is added, it holds brushstrokes well. In the picture below, when added to green earth artist oil (bottom center), the mixture of Impasto Medium (bottom left) extends the color and its consistency, while the mixture with Velázquez Medium (bottom right) gives the paint a long, ropy consistency.


Rublev Colours Velázquez Medium and Impasto Medium
A comparison of Impasto Medium (top left) and Velázquez Medium (top right) shows the different handling characteristics when added to paint (bottom).

How to Use

Mix Rublev Colours Calcite Mediums directly into your paint right on the palette with a palette knife.

Rublev Colours Calcite Mediums are a great way to add calcite to your own paint. Add the medium with linseed oil directly to pigment powder until a stiff paste is obtained (almost the consistency of putty). Grind the paste with a muller on a flat surface before storing in collapsible tube. Some of its properties will be temporarily lost when grinding the medium with a muller, but should be restored when allowed to stand.

Paste Mediums Questions and Answers

As calcium carbonate, how is calcite different from using marble dust?

Calcite is the calcium carbonate mineral found in such rocks as chalk and marble, which both are varieties of limestone. The difference between calcite from marble and that from chalk deposits is the crystalline structure and the minerals often associated with each type of rock. Marble is an angular crystalline variety of limestone that differs in its shape to chalk. For this reason, marble is more often ground coarse and hence used to impart texture to products. However, comparable grades of calcite from marble or chalk can be found today. The quality of the marble dust or chalk should be evaluated based on the fineness of its particle size and the whiteness of the material.

I would like to use calcite ground or mixed with a knife in oil or medium as an additive to make paint transparent. Can I make it myself using the raw materials?

Yes, you can make your own calcite mediums or add calcite directly to paint and we encourage artists do to so by providing all the raw materials needed. The two calcite mediums offered by Natural Pigments, however, provide a convenient way to use calcite in your painting without the trouble of grinding the powders and mixing the oils. In addition, Natural Pigments has carefully formulated the mediums to provide widely different painting characteristics, which would be difficult to achieve without much trial and error.

What is the appearance of calcite mediums once dried?

Calcite mediums dry to a satin sheen. This, of course, can be varied depending on the oil color and other mediums and driers mixed with it.

What is the recommended ratio of oil paint to calcite medium that can be used safely?

Both Velázquez and Impasto Mediums have a high pigment load so you could apply them as pure medium to your painting the same as you would use oil colors. You can apply the medium as oil paint and it will dry similar to most oil colors. The satin sheen is consistent throughout. When added to color in increasingly larger amounts, it steadily increase the warmth of a hue and yet give it a clean translucent effect. You still have the option to add white for a cooler and possibly a more turbid effect in light values. There is no maximum amount either calcite medium can be used, since they are both essentially oils paints without driers, solvents and resins.

Can calcite mediums be used for other than painting impastos?

Even if you do not want textures or impasto in your painting, Velázquez Medium permits bodied highlights that level out yet achieve an optical effect of dimension usually associated with traditional painting. Velázquez Medium is excellent for making titanium white translucent and taking the edge of it's stark white and high tinting strength. Velázquez Medium is permits excellent control, dries well, and improves film adhesion. A small addition of Epoxide Oil speeds its drying time considerably and makes blending more effortless than Velázquez Medium alone. Its simple ingredients are a real plus and make a welcome addition to artists' painting materials.

Can I paint the upper layers using Velázquez Medium? I would probably thin it with the same oil I used in the painting, using more oil as the painting progresses.

There is no problem using Velazquez Medium in the upper layers of your painting, because it is a medium with a moderate oil content.


Gel Mediums

Rublev Colours Venetian Medium
Rublev Colours Venetian Medium

Rublev Colours® Venetian Medium

Venetian Medium is an oil-painting medium based on the research that 16th century Venetian painters added powdered glass to their paint. Venetian Medium contains leaded crystal glass powder, the palest bodied linseed oil and turpentine with small amounts of wax and lead drier. Spread thinly onto the surface and paint directly into it as a couch or add directly to paint nut. Smooths the edges of brush or knife strokes. Venetian Medium is fast setting and dries to a satin finish.

Venetian Medium is available in and 50 ml and 150 ml collapsible tubes.

How to Use

Spread thinly onto the surface and paint directly into it or mix directly into paint on the palette to give colors a flowing consistency that holds brush strokes yet dries to a satin finish. Use to "oil out" or as a painting couch by rubbing a thin layer onto completely dried paint. Gives paint a longer, flowing consistency.

Recommendation: To prevent Venetian Medium from skinning in the can while in storage, add a small amount of linseed oil, covering the surface of the medium.

WARNING! CONTAINS LEAD AND MINERAL SPIRITS. Do not take internally. Avoid eye and skin contact. Avoid long exposure by inhalation. Use with adequate ventilation. KEEP OUT OF REACH OF CHILDREN AND PETS. Conforms to ASTM D 4236 health requirements.


Rublev Colours Oleogel Medium
Rublev Colours Oleogel: Thixotropic Gel

Rublev Colours® Oleogel

Oleogel is a thixotropic gel painting medium made with linseed oil and pyrogenic silica. Oleogel is a clear pale amber gel that adds transparency and thixotropic body to oil, resin-oil or alkyd paint. Add directly to your paint to give it transparency without thinning its consistency. Add pigments or extenders to thicken it for creating impasto effects that do not sink in.

Oleogel does not contain driers, so it is safe to use in oil painting without worry of cracking. When mixed with colors, Oleogel does not slow the drying time.

Oleogel is available in 50 ml and 50 ml collapsible tubes and 8 fluid ounce (236.6 ml) cans.

Rublev Colours Oleogel Medium
Rublev Colours Oleogel and Lead White

Rublev Colours Oleogel Medium
Rublev Colours Oleogel and French Raw Sienna

Oleogel adds transparency to whites without losing the body of the paint. Oleogel is shown in the center with Lead White on the left and a mixture of Oleogel and Lead White on the right. The Lead White is stiff, plastic and short, but when mixed with Oleogel the mixture is semi-transparent, soft, yet sculptural.

What Customers Say About Oleogel

William Whitaker: I've found that it's easier to oil out with Oleogel than anything else I've used. There is much less tendency for the oil to bead up. Sometimes I use my fingers to apply it, sometimes I use a brush. The end result is a very thin layer – much like a well-oiled firearm. I don't use dryers, and I work on several paintings at a time, so I let days go by between sessions on a given painting, which allows the work to set well enough that the paint doesn't come up when I oil out.

Kenneth Freed: I have been using Oleogel as a wet cushion for some time now and have been very satisfied. Much of the usefulness of a wet cushion (whether it is Oleogel or other medium) depends on what you are trying to achieve. I reserve wet cushions for upper layers when I want to build translucent glaze and scumble layers. Adding Oleogel directly to the paint is an ideal way to control the quantity used in a painting and helps change the viscosity of the paint and the handling characteristics.

Steve Ladd: Oleogel has a really nice consistency, more like salve than another gel that I tried that just coagulated into gooey blobs. I like touching and smearing it around with my finger, and imagine that such rubbing will be part of my next painting. Maybe in a "wet cushion," although I don't paint in isolated sections of a painting, but am all over the place, so I don't know if I can use the wet cushion method.

Jive Dadson: I've been adding a little bit of stand oil to the Oleogel for oiling out and making a couch for glazing. The Oleogel provides the slicky, and the stand oil the sticky. Together the Oleogel and stand oil when added to paint behave somewhat like Maroger's medium. You can push the paint around on the support, but it stays in place. Add a tiny bit of linseed or walnut oil to the mixture, and it will level.

Oleogel increases transparency without flowout and leveling. In the image at right, Rublev Colours French Raw Sienna (left) is shown in a mixture of Oleogel and Raw Sienna on the right. Below each is a brush out of the above examples. Rublev Colours French Raw Sienna is long, yet holds strokes well. When Oleogel is added to Raw Sienna it increases transparency without causing flowout and leveling of brushstrokes, typical when mixing colors with bodied oil or thinners.

How to Use

Mix directly into your paint right on the palette.

To make your own paint with Oleogel, add directly to pigment powder until a stiff paste is obtained (almost the consistency of putty). Grind the paste with a muller on a flat surface before storing in collapsible tube. Some of its thixotropic property will be temporarily lost when grinding Oleogel with a muller, but should be restored when allowed to stand.


Rublev Colours Oleoresgel Medium
Rublev Colours Oleoresogel: Thixotropic Gel

Rublev Colours® Oleoresgel

Oleoresgel is a thixotropic gel painting medium made with bodied linseed oil, alkyd resin, odorless mineral spirits and pyrogenic silica. Oleoresgel is a clear pale amber gel that adds transparency and thixotropic body to oil, resin-oil or alkyd paint. Add directly to your paint to give it transparency without thinning its consistency. Add pigments or extenders to thicken it for creating impasto effects that do not sink in.

Oleoresgel does not contain driers, so it is safe to use in oil painting without worry of cracking. When mixed with paint, you may find that Oleoresgel slows the drying time. However, most artists who have used Oleoresgel find that it does not extend the drying time of oil colors.

Oleoresgel is available in 50 ml and 150 ml collapsible tubes.

How to Use

Mix directly into your paint right on the palette.

To make your own paint with Oleoresgel, add directly to pigment powder until a stiff paste is obtained (almost the consistency of putty). Grind the paste with a muller on a flat surface before storing in collapsible tube. Some of its thixotropic property will be temporarily lost when grinding Oleoresgel with a muller, but should be restored when allowed to stand.


Rublev Colours Wilson's Medium
Rublev Colours Wilson's Medium

Rublev Colours® Wilson's Medium

Wilson's Medium is a clear, gel-like oil medium based on the 18th century oil painting medium of thickened linseed oil, turpentine and beeswax used by the English landscape painter, Richard Wilson (1 August 1714–15 May 1782), who may fairly claim the honor of being 'the father of British landscape painting,' and, according to George Field, also used by Joshua Reynolds. We've taken the original formula and improved upon it by using the palest bodied linseed oil, pure distilled gum spirits of turpentine and rheological castor wax instead of beeswax.

Castor wax is obtained by the controlled hydrogenation of natural castor oil. When molten it is clear, transparent and largely colorless. Castor wax is practically odorless and has the same toxicity as linseed oil or other vegetable oils. Castor wax is extremely hard in comparison with most other waxes, so it can be used in much smaller amounts than beeswax to provide the same properties.

Wilson's Medium is available in 50 ml and 150 ml collapsible tubes.

Suggested Uses

Mix Directly with Oil Paints. No driers or resins are added to Wilson's Medium, so it can be safely added to oil paints. Mix it directly with colors to give oil paint a buttery consistency that holds brushstrokes yet dries to satin finish.

Use to Make Oil Paint. Add Wilson's Medium to pigment and oil when making your own paint. Paints often need the addition of rheological additives to prevent the settling of pigments during long periods of storage and to impart certain behavioral characteristics, such as to prevent slumping. Wilson's Medium changes the viscosity of paint by thickening it and imparts rheological properties, such as shear thinning (thixotropy).

Use to 'Oil Out' or as a Painting Couch. Wipe a thin coat of Wilson's Medium onto the surface of the dried paint just before painting a fresh layer. Wilson's Medium restores the dried, matte appearance of paint to a fresh appearance, without making it glossy.

How to Use

Spread thinly onto the surface and paint directly into it or mix directly into paint on the palette to give colors a flowing consistency that holds brush strokes yet dries to a satin finish. Use to "oil out" or as a painting couch by rubbing a thin layer onto completely dried paint. Gives paint a longer, flowing consistency.

Recommendation: To prevent Wilson's Medium from skinning in the can while in storage, keep the lid tightly closed.

WARNING! CONTAINS TURPENTINE. Do not take internally. Avoid eye and skin contact. Avoid long exposure by inhalation. Use with adequate ventilation. KEEP OUT OF REACH OF CHILDREN AND PETS. Conforms to ASTM D 4236 health requirements.


Rublev Colours® Italian Varnish

Italian Varnish was first mentioned by Jean-François-Léonor Mérimée in his 1839 book, The Art of Painting in Oil and in Fresco, as a “strong oil prepared in Italy from a very remote period, and which possesses the double-advantage of drying well, and preventing the flowing about of the most liquid glazing.” Italian Varnish is made using linseed oil, litharge, wax and a small amount of gum turpentine, ground as fine as possible. We have made it with some improvements to the method and materials given in the recipe by Mérimée. It is an amber gel medium that performs similarly to Maroger medium, except instead of mastic, this medium incorporates wax, which is ideal for those artists who prefer a thicker painting consistency and faster drying time.

Italian Varnish sets quickly, while providing translucency and body to oil colors when mixed with them in glazes. It gives a somewhat fluffy consistency to paint, making possible many different ways of using this subtle technique. In addition to the soft sheen of the medium, the artist now also has the means of more rapid execution. Artists can mix the Italian Varnish into light pigments (Lead White, Lead-Tin Yellow, Naples Yellow, Yellow Ocher, etc.) to give these colors more body and a thicker consistency. It can help to build up the lights and adds translucency and impasto for the brightest passages of a painting.

Italian Varnish is available in 50 ml and 150 ml collapsible tubes.

Suggested Uses

Mix Directly with Oil Paints. Mix it directly with colors to give oil paint a buttery consistency that holds brushstrokes yet dries quickly to satin finish.

WARNING! CONTAINS LEAD AND TURPENTINE. Do not take internally. Avoid eye and skin contact. Avoid long exposure by inhalation. Use with adequate ventilation. KEEP OUT OF REACH OF CHILDREN AND PETS. Conforms to ASTM D 4236 health requirements.


Gel Medium Questions and Answers

What is a thixotropic gel?

Thixotropy is the property of some fluids to change viscosity as they are agitated. The longer the fluid is agitated, the lower its viscosity. A gel is mostly liquid in composition, but behaves more like a solid. When a thixotropic gel is agitated, such as manipulated with a palette knife or brush, it begins to flow, but when the agitation is stopped it regains its former viscosity and stiffens.

What are the working properties of Oleogel and Oleoresgel?

Both gel mediums increase the transparency of oil colors without making paint more fluid, such as when adding drying oil to increase the transparency of a color. This is an advantage when you want a transparent layer of color without making the paint runny. The pyrogenic silica in these mediums add a little drag while brushing and its translucency creates wonderful possibilities for layered painting techniques.

Can I use Oleogel or Oleoresgel to make opaque impastos?

Both Oleogel and Oleoresgel increase the transparency of colors. Oleogel and Oleoresgel are soft gels so that as you add more to your paint the softer and more transparent it will become. For heavier impastos or textures, we recommend adding calcite (calcium carbonate) to Oleogel or Oleoresgel in combination with your oil colors. A more convenient method of building thick, opaque impastos we recommend using Rublev Colours calcite mediums, such as Impasto medium or Velazquez Medium instead of gel mediums.

I use a wax medium with my oil paint. Can Rublev Colours Oleogel or Oleoresgel be mixed with this medium?

Both gel mediums are compatible with wax pastes and resinous mediums. We do not recommend heating Oleogel or Oleoresgel to mix it with wax, but rather add the wax as a soft paste directly to the medium or melt the wax in linseed oil before adding it to Oleogel or Oleoresgel.

Can I add driers to Oleogel or Oleoresgel to hasten drying?

Oleogel and Oleoresgel do not contain driers, so you can add driers to it to speed its drying time. You will most likely find that driers are not needed. However, if you find driers necessary, add them as you would normally use with oil paint. We recommend adding one or two drops of zirconium drier or lead drier for each tablespoon (5 ml) of medium or the combination of medium and oil colors.

Can Oleogel be mixed with some turpentine to make a more liquid medium or would that negate it's inherent properties?

It can be blended with turpentine without any detriment to its overall properties, except that you no longer have a gel.

Can I use Oleogel in "wet cushions"?

For best results, Oleogel shoud be applied whisper thin. You have to take your hand and squeegee it off to a very thin application. Also, do not apply it as a wet cushion onto areas that you will not work over. You really don't want layers and layers of Oleogel without paint being worked into it.


Liquid Mediums

Rublev Colours Balsam Essential Oil Medium
Rublev Colours Balsam Essential Oil Medium

Rublev Colours® Balsam Essential Oil Medium

Rublev Colours Balsam Essential Oil Medium is composed of Canada balsam, pale bodied linseed oil and spike oil. Add to colors for enamel-like effects, to achieve glow in glazes and facilitate fusion. (44% resin solution).

Add a small amount of Balsam Essential Oil Medium to your paint to make it brush out more easily, adhere better to previous layers, and dry more quickly. Keep the bottle covered to limit evaporation, although you can dilute it with spike oil. Balsam Essential Oil Medium smells wonderful.

Canada balsam is a sap from fir trees. Although not a true balsam, this volatile resin can improve adhesion from one paint layer to another and impart a certain silky smooth quality to paint. Canada balsam is clearer and faster-drying than other resins, such as Venice turpentine.

Spike oil (essential oil of certain parts of the lavender plant) is an organic solvent, like spirits of gum turpentine, except that it evaporates more slowly. It has a very strong and agreeable smell. It has a long history in oil painting: Leonardo da Vinci is believed to have used it for the initial dark underpainting in his "sfumato" technique.

How to Use

Mix directly into paint on the palette to give colors a flowing consistency yet dries to a satin to gloss finish, depending upon the amount used. Use to "oil out" or as a painting couch by rubbing a thin layer onto completely dried paint. Gives paint a flowing consistency.

Balsam Essential Oil Medium is available in 100 ml and 250 ml glass bottles.