MEDIUMS FOR OIL COLOUR
The purpose of a medium is to influence one or more properties of the paint and to make the paint suitable for a certain application. Examples include consistency, gloss, flow, drying time, transparency and durability of a paint film. As an underlying (lean) layer absorbs oil from a subsequent layer, a subsequent layer has to contain relatively more oil. Think of the rule, fat over lean.
WHAT IS PAINTING PASTE AND WHEN AND HOW IS THIS MEDIUM USED?
Painting paste is an unpigmented (colourless) oil paint. The medium can be mixed with oil paint in any proportion without the paint losing its colour and consistency. This allows more paint to be made from very expensive colours.
Painting paste can also be used to prevent certain colours from wrinkling on the surface when applied in thick layers. A mixture combination in the ratio 1:1 is sufficient for this.
Painting paste does not yellow and increases the durability of the paint layer. The paint becomes a little more matt and the drying time decreases a little.
DOES A MEDIUM HAVE TO BE USED WHEN PAINTING WITH OIL COLOURS?
Whether a medium is used depends on the chosen technique. With oil colours there are two possible techniques: ‘Allaprima’ and ‘layered painting’.
‘Allaprima’ means that the painting will be painted ‘wet-into-wet’. With this technique the colours are mixed not only on the palette but also on the painting itself, and the paint can be continued to be thinned with the same solvent or medium, or the paint can be used pure.
Layered painting means that the painting is made up of various layers. A subsequent layer can only be applied once the previous layer is dry enough for it to no longer dissolve. Meticulous use of the various solvents is advised in connection with the adherence of the individual layers. Through anchoring, oil colours adhere into a porous ground. If a thick layer of pure oil colour were to be allowed to dry, then this would not be porous enough for a good adherence of the next layer.
Layered painting uses a technique that is called ‘fat-over-lean’, which also can be described as flexible over less flexible. For the first layer the paint is thinned with white spirit or turpentine. Due to the thinning there is relatively little oil on the painted surface. The layer is ‘lean’.
WHAT CAUSES THE RAPID DRYING FROM A QUICK-DRYING PAINTING MEDIUM?
A normal painting medium is a mixture of (linseed) oil, solvent (white spirit and/or turpentine) and the resins dissolved in the solvent. The solvent evaporates from the paint, the resins strengthen the paint film and the oil is responsible for the drying time. Linseed oil dries chemically. The oil absorbs oxygen from the air, resulting in the molecules linking to one another in firm chains. This process takes a long time and explains why it takes oil paint so long to dry.
If we want the paint to dry more quickly then we have to add something to the paint to enable it to take up oxygen more quickly. This is done with solutions of certain metal compounds, called siccatives, that can be added directly or via a medium. A quick-drying medium therefore consists of the same ingredients as a normal medium, but with the addition of siccatives. Siccatives can also be bought pure and can cause problems if used in high concentrations. The amount in Talens Painting Medium Quick-drying 084 is safe for the durability of the painting.
Once the first layer is dry enough, the second layer is applied, thinned with Painting Medium. Talens Painting Medium consists of three components: oil, resin and white spirit. The extra added oil feeds the lean first paint layer by filling the pores that are formed by the evaporated solvent. At the same time this second layer can also adhere well to the underlying layer. The evaporation of the white spirit forms new pores which allow for the adherence of a subsequent layer. The third ingredient, resin, makes the paint layer stronger.
If we apply a third layer, we need to use a medium that is fatter still in order to feed and strengthen the underlying layers. If a painting is made of more layers, then the mentioned thinning agents can be mixed proportionately from lean to increasingly fatter.
The last layer to be applied is usually a glazing paint layer. Glazing is the application of a transparent layer of paint. No brush stroke may be seen in a glaze as the brush strokes of the underlying paint are visible. Various glazing mediums can be used, such as Talens Glazing Medium, Alkyd Medium, Venetian Turpentine and Stand Oil. These mediums are fatter than the painting medium and allow the paint to flow without showing any brush stroke.
HOW DO I USE AN ALKYD MEDIUM?
Alkyd Medium can be used as both a glazing medium and painting medium. If used as a painting medium the “fat-over-lean” technique must be used. The medium is fairly ‘fat’ and can be made leaner through the addition of white spirit or turpentine. For the last layer and for glazing techniques Alkyd Medium can be used pure. It yellows somewhat, shortens the drying time and increases the durability of the paint film. It increases the gloss of the paint a little, and decreases the brush stroke.
WHEN IS GLAZING MEDIUM USED?
Talens glazing medium is the modern replacement for traditional glazing mediums such as stand oil and Venetian turpentine. It differs in its non-yellowing paint layer. The medium increases the flow as well as the gloss of the paint, does not affect the drying time and can be thinned with white spirit or turpentine. Only to be used in the final layers.
24xxxxxx TALENS MEDIUMS FOR OIL COLOUR
24280007 TALENS ALKYD MEDIUM 75ML
24280083 TALENS PAINTING MEDIUM 75ML
24300083 TALENS PAINTING MEDIUM 250ML
24320083 TALENS PAINTING MEDIUM 1000ML
24280084 TALENS PAINTING MEDIUM QUICK DRY 75ML
24300084 TALENS PAINTING MEDIUM QUICK DRY 250ML
24320084 TALENS PAINTING MEDIUM QUICK DRY 1000ML
24280086 TALENS GLAZING MEDIUM 75ML
24300086 TALENS GLAZING MEDIUM 250ML
24060096 TALENS PAINTING PASTE 60ML