Enamel Paints

THE TECHNICAL SIDE: ENAMEL PAINTS^*

Anthony Wood, FSHA

Newsletter No. 8, Spring 1992

Most of us who paint our heraldry probably work quite happily with gouache and acrylic on various absorbent surfaces, but what about a more impervious material such as metal, lacquered wood, or the paintwork of a limousine? The only easy answer must be enamels which have been made popular by Humbrol in their extensive modellers’ ranges. These tiny tinlets may be easily obtainable from any toy or model shop, but they have distinct disadvantages. To enhance their flow – so important when reproducing an aircraft finish in a small scale – they have increased the proportion of medium to pigment. This has the result of reducing the opacity, necessitating double coats of most colours or even more where the pigment used is naturally translucent. If these paints have been on the shelf for any length of time, which often happens with the slower moving specialist modellers’ ranges, the pigment settles and eventually forms a lump with a concrete-like resistance to being stirred.

As an alternative for our uses there are two easily obtainable ranges of signwriters’ enamels, one available over the counter, one by post from the importers: Signwriters’ enamels have the advantage of being perfected in use by the exacting demands of commercial craftsmen who will not tolerate an inferior quality product. When paint is manufactured, the pigment is passed through a mill to grind it. Most paint is ground twice, but the pigment for signwriters’ paints is put through three times, This removes any tendency towards graininess, especially with earth pigments such as the siennas and umbers, and enhances the flow without sacrificing opacity. After all, a signwriter cannot afford to spend unnecessary time re-coating work; it either makes him too slow to be commercial, or too expensive to be hired in what is a very competitive business.

Most signwriters’ enamels have a very high gloss which will often remain on an outside job when the cheaper paint surrounding it has become matt. Indeed, these paints are so durable that very old signs will often have paint peeling away from the wooden background, whereas the lettering is still intact.

The other advantage they have over the hobby tinlets is price. Although they vary according to the value of the pigments involved, a 14ml tinlet of Humbrol enamel retails at 65p. Keeps Signwriters’ Red, available in 250ml tins costs £5.96 while One-Shot Bright Red is £5.02 for 236ml. Worked out pence per ml, the signwriters’ enamels are about half the price.

Some may be used straight from the tin, while others are much more viscous to allow the painter to prepare them as he prefers. To do this, dispense the required amount into a suitable container. any signwriters use dippers which clip on to palette boards, but these can be messy and difficult to clean out if you are not used to using enamels. Proprietary porcelain paint palettes are not recommended, for the same reason. Rather, 35mm film cassette containers are useful and can be thrown away after use. Do not use flimsy plastic pots, however as the solvent in the paint attacks the plastic and eats out the bottom, with disastrous results for the studio floor

A few drops of raw linseed oil will enhance the flow, acting much the same as a drop of detergent on a pool of water. Be very cautious, though. One or two drops are usually enough. It also retards the drying properties of the paint which will be very obvious if you add too much.

White spirit is usually used to thin it to a working consistency, but certain pigments react unfavourably, losing their gloss very quickly. I have found the simple substitution of turpentine alleviates this problem, but turps and white spirit when mixed can sometimes set up a reaction in the paint, causing it to curdle as will happen if unused quantities are returned to the tin. To avoid this it is advisable to use only one type of thinner.

Signwriters’, ticket writers’ or poster writers’ brushes are best suited to these paints. Ticket and poster writers’ brushes have shorter lengths of hair and are easier to handle, especially when producing artwork. The deliberately shaped artists’ pointed brushes, as pushed shamelessly by model shops, are useless for all but the finest of detail work. The chisel ended tip of the professional brush will cover an area evenly with few brushmarks which will flow out as the enamel dries. Signwriters’ pointed brushes can be used most effectively for fine detail work, the length of the sable filling allowing a much longer line to be run than an artist’s brush.

If you already work in a water-based medium such as gouache, you will have favourite brushes for certain tasks. Do not use these for enamel work! Play around with less favoured brushes to start off with, as they must be cleaned quite carefully. After use, any paint which remains hidden in the ferrule will dry, eventually splaying out the hairs and cracking them, which is the end to a perfect brush. After thorough cleaning in white spirit or paraffin – which is a viable alternative for cleaning – pack the hair filling in vaseline or another non-setting grease. Work it well into the ferrule with your fingers, without damaging the hairs. This will prevent any paint still in the heel from setting. This is a superb way to store brushes, either briefly or long-term. When you next come to use the brush, wash it out again in solvent. The grease will be removed, pulling out any remaining paint and a clean, dust-free brush is ready for use. If you use gouache in a brush after this treatment, it will siss on the paper, as if it is covered in grease spots. To prevent this, work powdered chalk or whiting into the filling. This absorbs any remaining traces of grease which can be easily rinsed out in water.

For those of you who may wish to buy some, the following may be of interest; Bollom produces Keeps Signwriting Enamels in 29 colours including black and white. Available in 250m1 tins. They have been the British signwriters’ main suppliers for generations, but their range has altered little to cope with the changing design requirements of recent years, while some of their colours are almost duplicates of each other. The two creams are beautifully mellow in appearance but often require three coats to cover; the browns and ochre are fully opaque; “Poppy” is opaque, but “Signwriters’ Red” is not; the light blues cover well, while the dark blues are notoriously translucent; the greens are fully opaque; the burgundies are hard to cover, often requiring three or more coats, and are very slow to dry; the four yellows are useful in their varieties of chromes, but only “Middle Chrome” is anything like opaque.

This superb range of paints have been to the American sign painter what Keeps have been to the British signwriter. Available through a UK importer since 1985, their original range of twenty-one colours has recently been increased by fifteen! Signwriters have traditionally mixed their own colours as each job required, which has rather limited the interest of the paint manufacturers in extending their ranges. It is, therefore, a refreshing change to find a company who are moving so readily with the times. All colours have superb opacity except the greens and browns, strangely enough, which are to be avoided. Their cream (“Ivory”) is a very cool colour; there are now two turquoises, a mid-blue type and a light green version. The “Imitation Silver” and “Metallic Gold” are both metallic colours, They cover well but brush marks can be a problem with large areas, especially of the silver. Linseed oil helps to retard the drying time long enough for the paint to be laid off in one direction so all the pigment particles flow one way. These two, like all the range, are durable outside, and are especially noteworthy in that they do not tarnish, unlike bronze powders, the only alternative for a metallic finish unless gilding is undertaken.

Whilst on the subject of gold, both manufacturers produce a specially mixed dark cream which they market as “gold” paint: Keeps as “Gold Colour”, and One-Shot as “Imitation Gold”. When viewed from a distance of, say, fifteen feet or more they both have a remarkable gold-like appearance, only lacking the lustre of gold leaf. The American version has a much richer gold appearance but often looks gaudy unless used with care.

Mention must be made, finally, about Synthetic Enamels. A typical range is Standox Superfleet, which is occasionally used by the faster signwriters for vehicle painting. Designed for application by spray, they can be brushed, but if overbrushed will drag badly. They dry very quickly and can be overcoated within a couple of hours or so. Their adhesion to the stove enamelled finish of a new car is far superior to other enamels, but they are only recommended for large commercial use and are not for the faint-hearted!

Drying times on these paints vary according to pigment and weather conditions, but an average time would be touch dry two hours, handling eight hours, overcoating sixteen hours, Caution must be exercised when overcoating two or three times, as the paint will wrinkle if it is not thoroughly dry, and still remain soft for several days, being readily marked by fingerprints or bubble packaging.