Frequently Asked Questions - General Oil Colour
You will find below a selection of FAQs relating to using oil colour in general. If you still can't find the answer you're looking for you can email us.
1. "Oiling out" is recommended for dull areas of a completed oil painting, how is this done?
2. What is the "fat over lean" painting rule?
3. What are the three basic oil painting rules?
4. What are the best brushes to use with the Winsor and Newton Oil colour ranges?
5. What is the cause of an oil painting getting progressively duller as layers are added?
6. How can oil colours be prevented from sinking?
7. Can different oil colour media be mixed?
8. Do oils have to be used as well as solvents when painting with oil colour?
9. How do the types of linseed oil differ?
10. How do Poppy and Safflower oil differ from traditional Linseed oil as mediums?
11. Why should an oil painting be varnished?
12. How should an oil painting be varnished?
13. How can I tell when my oil painting is fully dry?
14. How can an artists' varnish be removed from a painting?
1. "Oiling out" is recommended for dull areas of a completed oil painting, how is this done?
Oiling out is the application of an oil medium to a painting which has sunk (become dull), or lost its oil to the layer underneath. The most common causes for this are an over-absorbent, cheap ground or the use of too much solvent and insufficient or no medium. When the colour is dry, Artists’ Painting Medium should be sparingly rubbed into any sunken areas with a clean cloth.
Wipe off any residue and leave to dry for a day or two. If smaller, dull areas remain, repeat the process until the painting has regained an even sheen. Varnishes should not be used for the purpose of recovering the lustre of a dead painting. For a faster drying oiling out medium, use Thickened Linseed Oil diluted with 50% white spirit (mineral spirits).
For further information click here.
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2. What is the "fat over lean" painting rule?
Fat over lean is better understood if considered as ‘flexible over less flexible’. When painting in layers, the proportion of medium used in each layer should be increased. The higher proportion of medium makes subsequent layers more flexible and prevents the painting from cracking. This rule has traditionally been kept by adding more and more oil to the solvent used. However, as Liquin is now more commonly used, it is the Liquin content which is increased. There is no need to use oil as well.
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3. What are the three basic oil painting rules?
When painting with oil colour, artists must adhere to three conventional oil painting rules:
1. Fat over lean - (see explanation below). When oil painting in layers, each successive layer must be more flexible than the one underneath. This rule is maintained by adding more medium to each successive layer.
2. Thick over thin - Thick layers of oil colour are best applied over thin under layers. Thin layers on impasto paintings are likely to crack.
3. Slow vs. fast drying colour - Slow drying colours should not form continuous under layers as any faster drying layers on top may crack.
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4. What are the best brushes to use with the Winsor and Newton Oil colour ranges?
There is one main benchmark for brushes that are used with thick or viscous colour; the thicker the colour, the stiffer the brush needs to be. A heavy paint like oil requires a brush with enough resilience to manipulate the colour with complete control.
However, a colour that has been thinned will need softer tuft (e.g. soft hair or filament) and a colour that has been thinned to a fluid consistency needs a brush with flow control (e.g. synthetic or natural hair brush such as sable).
For further information on how to choose an Oil Colour Brush click here.
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5. What is the cause of an oil painting getting progressively duller as layers are added?
This is called ‘sinking’ and is a result of the ground or underlayer being too absorbent. If the sinking is consistent over a large area then this would indicate the ground is too absorbent. This is common when household emulsion is used for a primer. Artists’ primer properly applied on your next canvas will be less absorbent.
However, when building up oil colour in layers, the different drying rates can also result in a paint film with varying absorbency. This is usually indicated by dull spots rather than complete dull areas. In either case, dull areas must be treated, or as you have found, any further layers will only continue to sink. The absorbent areas are drawing the oil from any fresh colour which is applied.
Dull areas should be ‘oiled out’ using Artists’ Painting Medium from Winsor & Newton. Rub this sparingly into the affected areas and leave to dry. This is a stand linseed oil/white spirit mixture. Repeat as necessary if any smaller patches remain.
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6. How can oil colours be prevented from sinking?
Sinking is the most common problem for oil painters. It is usually down to one or both of the following;
a) a too absorbent ground, typically household emulsion,
b) too much solvent or a lack of medium. Make sure you use Winsor & Newton primers to prevent sinking and use medium in addition to solvent as you work.
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7. Can different oil colour media be mixed?
All types of oil colours can be safely intermixed with two exceptions; I] heavy underpainting in Oilbar is not recommended beneath oil or alkyd colour. Thick Oilbar films are likely to be too flexible due to the wax content. Ii] thin alkyd films are not recommended on top of oil or Oilbar films. Thin alkyd films may be too inflexible over the relatively more flexible oil or Oilbar films.
In both cases the ‘flexible over inflexible’ [fat over lean] oil painting rule is being broken. If painting with Artisan we recommend using it exclusively to maintain its water mixability and prevent any difficulties in keeping the fat over lean rule.
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8. Do oils have to be used as well as solvents when painting with oil colour?
If paintings are completed in one layer or ‘alla prima’, using a little solvent (turps) only is fine. If painting in layers then it is necessary to increase the amount of binder in each successive layer. This is called ‘fat over lean’. This is achieved by reducing the amount of solvent and replacing it with oil or binder in each sucessive layer. Fat over lean is a necessary oil painting rule which prevents cracking.
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9. How do the types of linseed oil differ?
Cold Pressed Linseed Oil will dry slightly quicker than Refined Linseed Oil and may have better flow with some colours. Bleached Linseed Oil is paler than refined for mixing with whites and blues and dries quicker. Stand Oil is paler and thicker than refined and is the slowest drying linseed oil. Drying Linseed Oil is the fastest drying linseed oil.
For further information on Drying Oils click here.
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10. How do Poppy and Safflower oil differ from traditional Linseed oil as mediums?
Poppy and safflower are classed as semi drying oils, whilst linseed is a drying oil. Semi drying oils are paler than linseed but dry more slowly. Safflower oil is not available as a medium. Poppy oil is supplied as Drying Poppy Oil, which has added driers to it. This provides a pale medium for use with whites and blues but with a comparable drying rate to linseed to help avoid cracking.
For further information on Drying Oils click here.
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11. Why should an oil painting be varnished?
Varnish is desirable for two key reasons: one, to bring the surface to a uniform gloss level (matt or gloss or somewhere in between), and; two, for protection from dust and other atmospheric contaminants.
For further information on why, what when and how of varnishing click here.
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12. How should an oil painting be varnished?
Varnishes are used to protect the finished painting. Picture varnishes should be removable so that paintings can be cleaned when they have become dirty.
There are two important things to remember about varnishes:
• Don't varnish too early, even the thinnest oil painting should be allowed to dry for 6 months. A minimum of one month is required for thin Griffin alkyd paintings.
• Don't use varnishes as mediums, this would make the painting sensitive to solvent. An attempt to clean it in the future may remove the painting instead. Here are eight simple steps to varnishing success:
1) Use a 1”- 4” flat wide, soft, tightly packed, varnishing brush (such as the Winsor & Newton Monarch glazing/varnishing brush). Keep it clean and use it only for varnishing.
2) Place the work to be varnished flat on a table - do not varnish vertically.
3) Apply the varnish in 1-3 thin coats, rather than 1 thick coat. A thick coat will take longer to dry, may dry cloudy, drip or sag during application and has a greater chance of showing brush strokes when dry.
4) Thinned varnish is more susceptible to producing bubbles. Do not be vigorous in your application.
5) Apply in long even strokes to cover the surface top to bottom while moving from one side to the other. While working, inspect the varnish layer at all angles for bubbles. Even them out immediately.
6) Once you leave an area, do not go back over areas that you have done. If you do, you risk dragging partially dry resin into wet, which will dry cloudy over dark colors. If any areas were missed, allow to dry completely and re-varnish.
7) After varnishing, it is recommended that the surface should be shielded from dust with a protective plastic film “tent”.
For further information on how to varnish an oil painting click here and varnishing click here.
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13. How can I tell when my oil painting is fully dry?
Dip a lint-free rag in solvent such as Winsor & Newton Artists' White Spirit, and rub gently on the painting surface. If colour shows, additional drying time is needed. If not, your painting is ready to be varnished.
For further information on solvents click here.
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14. How can an artists' varnish be removed from a painting?
If the painting is particularly valuable then it should be taken to a conservator.
Otherwise, the best product to use would be our Distilled Turpentine. For further information click here.
Dip a lint free cloth into the turps and gently rub the surface of the painting. Start in a corner. The varnish should come off onto the cloth.
If any colour can be seen on the cloth then you should stop. Working in small squares, proceed across the entire surface of the painting. It is best to keep using fresh pieces of cloth as this aids lifting the varnish rather than spreading it.
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