Any solvent used as a vehicle to carry pigments in paint is known as the 'medium' or 'glaze'.
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Water-based glaze
Oil-based glaze
Cheaper alternatives
Not sure which?
Acrylic or Water-based medium.
There are many pre-tinted and un-tinted water-based glazes on the market today.
Alternatively, you could make your own water-based medium or glaze using cheaper alternatives
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Oil-based medium.
If you wish to produce any of the effects shown here using oil-based products, use the following formula as a guideline:
Mix 1 part raw linseed oil with 3 parts white spirit or turpentine.
Then add a small amount of liquid driers (1 teaspoon per 1 litre of the mix).
Use a little less driers in a warm dry environment, and a little more if cold and damp.
Mix this "medium" with your oil-based topcoat in a ratio of:
1 part paint to 1 part medium for 'glaze' or
1 part paint to 3 parts medium for a 'wash'.
Use oil-based mid-sheen paint for the basecoat. Protect your work using oil-based varnish if required.
!!! With oil-based method, used rags etc must be laid flat and allowed to dry before discarding to prevent spontaneous combustion !!!
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Cheaper alternatives.
Not all paint-effects require specialist paints with added 'extenders' known as 'glaze'.
Additive techniques such as
ragging-on &
sponging-on can be produced using ordinary water-based paint.
There are also cheaper ingredients that you can add to your paint to extend the 'open time' such as:
1 tablespoon of Glycerine (available from most chemists/drug stores) can be added to 1 litre of thinned water-based paint.
Most paints contain pigments, diluents and binder.
The pigment is the colour available in tubes (artists oils, acrylics & gauche), as powder, or pre-mixed colourisers & stainers.
The diluents are the solvents or thinners, used to dilute the paint (turpentine for oils, water for acrylics & emulsion).
The binder carries and fixes the pigment & forms a protective film (linseed oil for oil paint, acrylic resin for emulsion).
You can use the following as a binder & diluent combination, in which to add your pigment:
Stale beer or vinegar; thinned with 3 parts water. (not recommended for beginners)
1 pint of white distilled vinegar and 1/4 tsp. household detergent or sugar. Add dry colour (powder), tempera or gouache.
Fuller's earth, PVA or rabbit-skin glue; thinned with water only.
Skimmed milk; thinned with equal parts of milk & water.
N.B. These mediums are reversible (they must be sealed with a non-water-based coating when dry).
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Water-based V's Oil-based
Certain factors should be taken into account when deciding which medium to use:
Water-based paints are more prone to knocks and scratches, which makes them more suitable for walls than for woodwork.
Oil-based paints will withstand these knocks and scratches better and are therefore more suited to high-traffic areas.
Oil-based paints can be applied over water-based paints, usually without any difficulties.
Whereas, applying water-based paints over oil-based paints can produce problems such as cissing.
Cissing can be avoided by washing the oily surface with an emulsifier such as "fuller's earth" or household detergent.
Advantages and disadvantages:
Oils -
are the traditional medium for decorative painting and are especially suitable for graining and marbling.
Oils are useful for beginners, as they remain 'open' longer, thereby allowing ample time to create the effect and correct mistakes.
The drying time can be altered easily by the adjusment of the oil-to-dryers ratio, to suit the desired effect, the climatic conditions, etc.
However, the slower drying time means a longer wait before re-coating the surface with more glaze or with varnish.
Oils are also flammable and produce strong vapours that can affect people with breathing difficulties such as asthma.
Water-based paints -
are virtually odourless and need only water for thinning and cleaning.
The faster drying-time is an advantage where an effect requires the build-up of several layers within a short time span.
It also accumulates less dust, and the 'darkening' or 'yellowing' with age, so noticeable with oils, is virtually non-existent.
However, this faster drying-time requires more skill to create the effect before the glaze becomes too dry to manipulate.
The quick-drying nature of water-based glaze also makes it unsuitable for use on large unbroken areas.
It is also difficult to maintain an even thickness on undulating surfaces, such as moulding, and at the ends of panels etc.
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