MEDIUMS Mediums are resin-based thinners that allow the artist to superpose layers of paint more rapidly without the new colours soaking through to the ones underneath. They also ensure that the painting dries better to the core and increase the suppleness of the paint film over time, thus delaying the appearance of cracks. With different combinations, artists can increase or decrease the setting time, change the shading, texture and adjust the brightness and transparency of their work. When using oil paint, be careful never to paint too lean (dilute with solvents instead of mediums): when the varnish is applied, the picture varnish will fusion with the paint layer. The consequences are serious because any future varnish removal and restoration will become impossible.
SICCATIVES Siccatives have two functions: 1)In thick paint, they artificially increase the siccativity of colours with limited drying potential (which remain sticky 10 days after being applied, this is the case for reds with a base of quinacridone pigments and ivory black). Care must be taken because the paint from manufacturers already contains siccative in its formulation. This is why one should never exceed the dose of 1 drop of siccative for 1 thimbleful of colour (approx. 2 cm3). Adding too much siccative can create the opposite effect and cause cracks to appear prematurely on the painting. 2) For those artists that make their own colours, siccatives are essential additives (added to the oil) to control the drying rate of the pigments. With age, the various paint layers will have the same hardness and the picture layer will be more uniform. From 30 July 2002, date at which the European laws onthe labelling and sale of dangerous products changed, the lead siccative was replaced by a zirconium siccative that is much less dangerous and just as efficient.
RETOUCHING VARNISH Retouching varnish is used to eliminate sinking (areas of a painting that become matt owing to the absorption of the resin and/or oil by the underlying layers). It is also essential when retouching old paint that has dried out, to ensure a link between the old layer and the new layer of colour. Finally, it is also used as a temporary varnish while waiting until the final varnish can be applied. Caution: Never apply the final varnish to an oil painting before 6 months to 1 year. The consequences are serious because any future varnish removal and restoration will become impossible.
PICTURE VARNISH The role of picture varnish is to protect paintings efficiently against dust, smoke, scratches, atmospheric pollution, etc. It is also used to give your paintings a smooth glossy or satin finish. Caution: Never apply varnish to an oil painting before 6 months to 1year, so as not to cause the varnish and paint to knit together. Theconsequences are serious because any future varnish removal andrestoration will become impossible.
MATT and SATIN VARNISHES Although remaining true to oil painting and its glossy finishes, a high gloss on the painting may sometimes be dreaded either through individual taste or for reasons of exhibition and lighting. Although it is relatively easy, using retouching varnishes, to counter the formation of undesirable sinking on a painting that one wants to be glossy, it is very difficult to avoid any glossy areas on paint that one requires to be matt. The answer is to use a glossy varnish and then to overlay a matt varnish when dry. Instructions for use: The presence of undissolved material can give matt varnishes a cloudy aspect or create a deposit. In no way is this a sign of deterioration. However, all matt varnishes must be shaken energetically and stirred (e.g. with the handle of a paintbrush). Mixing in this way makes the varnish uniform and fluid.
GLOSS VARNISHES To determine the varnishing degree of the glosses, the percentage of dry extract must be known: The higher the level, the more resin is deposited and therefore the more the varnish appearance is glossy. Some varnishes have a synthetic resin base and can be used for oil and ACRYLIC painting. Others are made from natural resins and are only used for oil painting.
SOLVENTS Solvents are used to dilute the mediums and paint for the first layers of the painting. Next, the quantity of solvent must be reduced so that the “lean to fat” rule is always followed. Caution: When using oil paint, be careful never to paint too lean (diluted with solvents instead of mediums): when the varnish is applied (even after 6 months to 1 year), the final varnish will fusion with the paint layer. The consequences are serious because any future varnish removal and restoration will become impossible.