This article will provide general information about the different types of paint mediums that are commonly used by scale modellers.
There are many different types of paint on the market. For modellers, acrylics and enamels are the most widely used and each one has it’s advocates. However, there are several other types that can come in useful from time to time and it is a good idea to be aware of all the different types and their characteristics.
Common Ingredients Of Paint
All paints are made up of the following constituents:
This is what gives the paint it’s colour and ability to hide what is underneath it (opacity). The pigment is all important, particularly to modellers. Because of the fine detail and thin coats demanded by modellers, the pigments in model paints have to be ground much finer than conventional paints. Permanence or ‘light fastness’ is also an important factor when considering pigments – some cheaper paints will contain pigments that may fade over time, particularly when exposed to bright sunlight.
In metallic paints the pigment is often very finely ground particles of metal. Varnishes are often paints with the absence of any pigment.
Binder / Vehicle
This is the substance that makes the pigment particles stick to each other and makes the paint stick to the surface. The binder also determines many of the qualities of the paint such as how hard or flexible it will be when dry, how fast it will dry and how resistant it will be to abrasion and chemical attack. It is the binder that is the main difference between the different types of paint. Typical binders are acrylic resin and linseed oil.
Liquid / Solvent / Carrier/ Dispersant
This component can be called any one of the above names and it serves a number of purposes. A paint with just pigment and binder would probably be a thick unusable paste. The liquid is used to thin this to a consistency where it can be applied as a thin layer and where it will dry in a reasonable time. The amount of liquid determines the consistency of the paint i.e. how thick or thin it is and cheaper paints will tend to have more liquid and be thinner because this is the cheapest ingredient. Typical liquids used are white spirit, turpentine, water, cellulose and alcohol.
A paint may contain just the three components above, but some manufacturers will include small amounts of additives intended to affect the characterisics of the paint. These additives often explain why paints of different manufacturers behave differently.
Some of the effects of additives are:
- speed up or slow down drying time;
- Keep the pigment dispersed i.e. stop it settling to the bottom;
- change the surface texture (make the paint finsih more glossy or matt);
- modify surface tension and improve flow:
Types Of Paint
The types of paint covered in this article are:
- Enamel (modelling)
- Water Colour
Acrylic paints have an acrylic resin binder and use water and/or alcohol as a liquid. They are easy and safe to use, permanent, quick drying, low odour and are suitable for brush and airbrush. Currently, they are probably the most popular type of paint used in scale modelling.
Since acrylics can be thinned and equipment cleaned with alcohol or water they are very user friendly. However, care is needed because they can dry very quickly and when dried are difficult to remove – airbrushes should be flushed with thinner every few minutes of use with acrylics. Most manufacturers produce thinners for use with their own ranges and to be absolutely safe you should stick with these. Water and alcohol will act as a thinner with most paint ranges, but will not always give such good results and it is not always possible to mix acrylic paints from different manufacturers.
Acrylic paints have been available for a very long time, but traditionally were used by artists for painting pictures. Acrylics came as a thick paste in tubes which was either applied with a palette knife, or thinned with water for use by brush. When specific ranges were introduced for modellers in small pots, their low odour and low toxicity were emphasised rather than any of their other qualities. This gave the impression that they were suited to younger modellers and not equal to the existing enamel paints used by ‘serious’ modellers.
This is a pity because although acrylics are very different to enamels, they are every bit as good which is why they are used so widely today. However, it has taken a long time to squash the image of acrylics being for children. The one application where acrylics do not do well is where different colours need to be blended seamlessly, such as is often the case with figure painting. Some figure painters will use acrylics for the clothing, but stick with oils and emamels to paint the face.
|Saftey Advice: Whatever type of paint you are using you should wear a good respirator when airbrushing.|
A wide range of additives are available for acrylics to make them more or less glossy, transparent (glaze) and slow drying time.
Modelling enamels have an oil binder and spirit based liquid (white spirit or turpentine). I use the term ‘Modellilng Enamel’ on purpose to distinguish them from the normal enamel paints that are glossy paints used to cover kitchen appliances and often hardened in a kiln. Modelling enamals are quite different as they are air-drying and can be either a glossy or matt/flat finish. Modelling enamels are really thinned down oil paints and can generally be mixed successfully with oil paints.
Modelling enamels were the first type of paint to be specifically produced for modellers. They were generally offered for sale in small metal tins and the introduction of colours made to exactly match military aircraft and vehicles was revolutionary and welcomed with open arms by modellers worldwide.
Today, enamels are widely available from many manufacturers in a huge range of colours matched only by the ranges of acrylics available. Like acrylics they cover well and produce a durable finish. They are not as user friendly as acrylics because they have to be thinned with spirits that are inflammable, toxic and smell bad, but this disadvantage should not be over emphasised. Providing the room is well ventilated there should not normally be a problem. Enamels have the advantage that they are slower drying and even after they have become touch dry they can be softened again and removed with spirits which makes them less stressful when used in airbrushes.
I will not express any opinion as to whether acrylics or enamels are best because to favour either one would lead to me deeply offending a large part of the modelling community. Suffice it to say that I use both regularly and would hate to be without either.
Gouache (sometimes called Poster paint) is a water based paint similar to water colours (see below). It differs from water colours in having a coarser pigment and an additional inert white pigment such as chalk added. It has no practical use for modellers and is included here for completeness.
Care is needed with this term as it is often used to describe any sort of glossy protecive coating, for example furniture is often described as having a lacquered finish. Sometimes a paint may be descibed as a lacquer when in fact it is an acrylic or enamel based gloss varnish.
- Highly toxic and very strong smelling!
- Fast drying;
- Very flammable;
- Hard, durable, shiny finish (although some flat lacquers are available).
Cellulose paints are widely used in the auto industry and when you consider how hard wearing the paint job on a car has to be, you will realise how durable lacquer paints can be.
Because lacquers are very fast drying, highly toxic, flammable and very unforgiving they can be a real pain to use. However, they are popular with some modellers. The shiny hard wearing coat is ideal for auto models – particularly radio control which need to survive the real world. Lacquers are also great for realistic metallic finishes and one of the most popular ranges of metallic lacquers is made by Alclad and since full details of how to apply them are on their website I will not repeat them here.
Another range of lacquer paints popular with modellers is the ‘Mr Color’ range from Gunze Sangyo (not to be confused with their ‘Mr Hobby’ paint range). Tamiya produce a range of lacquer spray cans and Testors produce some clear lacquer coats under their Model Master range.
There is a wierd contradiction with lacquer paints and plastic modelling. Cellulose melts plastic, so you might think that you would not want to get a lacquer paint in direct contact with the plastic surface. However, there are some lacquer based spray primers. Because the lacquer spray is so thin, it dries within seconds before it does any damage to the plastic surface, but it just has enough time to key into the plastic giving it very good grip.
Lacquers will almost certainly need to be applied very thin by spray can or airbrush in a very well ventilated area and with a protective mask. Use only cellulose thinners and use them well and often if you value your airbrush. Alcohol, water and acrylic thinners will have no effect on lacquer paints except to make an dreadful mess – you have been warned. If anyone knows of a way to remove dried lacquer paint please let me know.
One problem you might find with using lacquer paints is getting hold of them in the first place. Due to their flammability many mail order and Internet shops will not ship them airmail so you might have to find a local source.
Personally, I would only use lacquer paints as a last resort, since I want to enjoy my hobby and they are just too unpleasant to work with. However, some modellers swear by them.
Oil paints have many similarities to modelling enamels having an oil binder and spirit solvent. They have been used by artists for many hundreds of years and are normally available from art shops rather than model shops since artists are still their main customers.
Oil paints come as a thick paste in metal tubes like toothpaste. Some artists may apply the paint thickly with a palette knife, but modellers will always have to add considerable amounts of thinner to get the paint to a consistency useful for scale modelling. They can be thinned with linseed oil which makes them glossy and slow to dry, or turps which makes them more matt/flat and speeds up the drying time (although it is almost impossible to get a true matt/flatt finish with oil paints).
For modelling purposes, oils are almost exclusively used for brush application – I have never heard of anyone airbrushing oils. They are popular with figure painters because they have a very slow drying time so can be blended giving soft edges. They are also frequently used for detail painting, filters and washes. Oils would not be considered suitable for painting a whole model.
Oil paints can seem expensive, but good quality oils are very thick and dense so last a very, very long time. With regard to quality, it should be noted that many of the better known manufacturers of oils (Winsor & Newton, Daler Rowney) make oil paints in two qualities. The best quality is always known as ‘Artists’ with the cheaper and inferior going by a variety of names like ‘Students’ and ‘Georgian’. ALWAYS buy artists’ quality, the pigments will be finer, more dense and have greater permanence.
Similar to water colours (see below) but the binder is a glutinous material such as egg yolk. It has very limited uses, but I have heard of one modeller using it for weathering and as a wash to show up panel lines. Like Gouache this is also sometimes referred to as ‘Poster’ paint.
Water Colours use a water-soluble carbohydrate as a binder and water as the liquid. They have been traditionally used by artists for hundreds of years. A feature shared with oil paints is that the main manufacturers make them in two grades with ‘Artists’ quality be the best and the one that modellers should stick with.
The most important feature of water colours is that they never become permanent. Even when completely dry they can be removed and washed away with water. This apparent disadvantage is what makes some modellers love them. They are of no use for painting the main body of a model, but can be very useful for weathering, or applying a wash to show up surface details or panel lines. Provided the model has been given a protective coat of varnish, the modeller can experiment with the watercolours in the knowledge that if the finished look is not good, then it can be washed away and they can start again. Although water colours are not permanent, they can be sealed in with a coat of varnish when the modeller is satisfied with the result. In this respect water colours are very forgiving.
Water colours are sold in two forms. They come as a paste in tubes, like oil paints, but the tubes are often smaller. They are also available in blocks often sold as sets. The blocks are called pans or half-pans depending on their size. These blocks are basically dried paint, but as mentioned above, water colours can always be brought into liquid form again with the addition of water. The pans are very portable so are popular with water colour artists who paint in the field. Modellers will probably find the tubes more easy to use.
Mixing Different Paints
The following are general guidelines. It would be impossible to test every brand of paint with every other brand, so it is advisable to do a test before applying any homemade paint mixture to your model.
As a very general rule, oil based paints generally mix well with each other, water-based paints may mix but care is needed. Never try to mix any water based paint with any oil based paint. Oil and water do not mix!
Enamels mix well with each other, even different brands and all can be thinned with white spirit or turps. The same applies to oil paints. Most enamels also seem to mix well with oil paints.
All acrylics can be thinned with water although the manufacturer’s own thinner may do a better job. Some acrylics can be thinned with isopropryl alcohol although the only advantage over the proper thinner is that it is cheaper. Acrylics from one brand may mix with those from another, sometimes they will not and will form into lumps. If you really need to mix two brands of acrylics, then do a thorough test first and see how the mixture dries.
Watercolors should be thinned only with water and not mixed with any other type of paint.
From time to time, manufacturers change their paint formula, so even if a mixture worked some time in the past, do not assume that it will always be so.
Drying and Curing
Just because a paint has become touch dry does not mean that it has fully cured. Acrylics may appear dry after only a few minutes but continue to cure and harden for several days. A paint will appear dry as soon as the ‘liquid/solvent’ in it has dried or evaporated. However, it will not be fully cured and hard until the binder has also dried or set.
It is normally possible to airbrush thin coats of paint one after another as soon as the previous coat has lost its sheen. Much more care is needed with brush painting when the coats are thicker and the brush may dislodge the previous paint layer.
It is also important to avoid sealing in a coat of paint that has not fully dried with another coat of a different type. For example, if putting a coat of acrylic varnish over a layer of enamel paint or vice versa you need to really sure that the coat being covered has fully cured.