USING DECALS

GETTING THE BEST FROM DECALS

At Red Roo Models, we are often asked about using decals. What type, how to apply them and get the best from them, how to repair them, how to handle them and so forth. On this page you'll find a few ideas on how to get the best out of your decals. But, before we start - a little diversion. How many people actually know the meaning of the word decal and its derivation? A decal is an object used for transferring pictures or designs from specially prepared paper to wood, metal, glass, plastic, china, etc. The word derives from the Hebrew degal, meaning flag. As such, it is one of only about 25 Hebrew words that made the transition into the English language. When the word originally appeared (in WWII US Army Technical Orders), it was printed in its full (or long version), decalcomania. This term referred to pre-printed adhesive national markings or instructions that could be applied to aircraft surfaces. The word was shortened into "decal", which we now use as a modelling term. Decals are also known by the term "waterslide transfer" or simply "transfer", which is used in standard English. Today the word "decal" is mostly used in Australian and American English.

	The arch enemy of modellers is "silvering", which is caused when the decal carrier film does not completely adhere to the surface of the model. Take a close look at this image of a 1/48 scale F-4. Note how the decals show signs of silvering.
	The way to avoid this problem is apply a coat of gloss varnish before the decals are applied to the model. Decals adhere much better to a gloss surface (because it is smooth) than to a matt surface. Once the decals have dried and settled in place, a process that usually takes a couple of days, the modeller can then apply a finishing coat of varnish, usually matt.

How Decals Are Made

The oldest form of printing is Letterpress (either rotary, flat-bed cylinder or platen) and is capable of very fine colour reproduction on coated papers or coarse printing on hand made paper. Letterpress is expensive and time consuming in preparation, unless rubber plates are used, and this precludes it from use in printing decals.

Lithography and its derivative, Off-set Lithography, have been used for many years. Working on the principle that oil and water don't mix this method can reproduce very fine images. Most plates these days are produced photographically and the image is reproduced in an off-set manner, ie, the ink is transferred from the plate to the paper via a blanket roller. Special care must be taken in preparing the plates to ensure colour separation is accurate ("in register"). Off-set lithography presses can be very large or very small and semi-portable. Colours sometimes can appear translucent. Fast printing outlets use this type of process.

Screen printing is used because it is fairly inexpensive and easier to maintain in register. The screen, through which the ink is squeezed, once a stencil is in place, may be made of silk, nylon, Dacron or metal and is stretched very tightly over a frame. A squeegee is passed across the screen and the ink makes the print by adhering to paper that is exposed by the stencil. Screen printing is very versatile and can use photographically produced stencils. It is recognized by the uniform layer of ink deposited and the opacity of the printed image.

For water-slide decals strong backing paper is selected and given a coat of "soft" (rapidly soluble) glue, followed by a coat of "hard" (slower soluble) glue, a carrier film, the various layers of coloured ink and a sealing varnish.

Artwork for the decal is usually prepared using a graphics programme at four to ten times the final desired size, then reduced to the desired scale and colour separated. This means an individual layer, plate or screen is made for each colour. Careful preparation is the critical step in making decals, for the artwork must be correct in subject, shape, size, scale, and fit the proposed kit correctly to avoid disaster. The creator must take into account the final shape of the surface on which the decal will rest and incorporate the correct dimensions when making the original artwork, as well as ensuring that the subject is correctly scaled down. If any of these aspects are incorrect, the decal will either not fit the surface of the model or it will distort the shape of the subject when applied.

In the case of dry-transfer decals, a carrier sheet is printed in reverse by a plate which is photographically prepared. Then a pressure sensitive adhesive is bonded to the ink. When the decal is rubbed down onto the final surface and burnished, it is permanently fixed in place on the model. Both the ink and adhesive must be flexible enough to allow for movement under pressure during application and thus avoid cracking.

Preparing To Apply Decals

Preparation of the model requires attention to three critical steps:  Finish all painting of the model.  Spray on a heavy coat of gloss varnish to completely cover the model. Let the model dry for a few days.

You are now ready to prepare your equipment and get stuck into putting those decals on. The following is a basic list of items for the application of waterslide decals and the reason for selecting them: 

1. A small piece of glass - used as a cutting surface. 
2. Cuticle scissors - to cut individual subjects from the backing sheet, leaving the carrier film intact and sufficient paper around the subject to allow for handling. 
3. Two number seven scalpel handles - fitted with a number 11 and a number 15 blade. The number 15 blade is curved and used for cutting the excess carrier film away from the decals because the curved cutting edge reduces snags. The number 11 blade is pointed and used to cut the backing paper when the subject is too small to manoeuvre scissors around. The number seven handle, although a surgical one, is long and costs less than a "graphic" handle. 
4. A twelve cm steel rule - to give a steel cutting edge. 
5. Scale rule - essential for measuring decals in scale. This will also help you when cutting out walkways, stripes, etc, which have to measured and cut to scale. 
6. Dividers - used to transfer measurements.
7. Sewing needle - for bursting bubbles that may form as decals settle into place on the model surface! 
8. A saucer - in which you will "float" your decals off the backing sheet for application. 
9. Long sharp/sharp tweezers - for handling decals by the backing paper. Sharp/sharp tweezers are tweezers in which both prongs are pointed and narrow, often with finely serrated jaws. 
10. Conical sable brush (Size One) and tissues - for handling the decals once they are wet. 
11. An eye dropper and strip of shiny plastic - for preparation and rescue of decals! Sometimes, decals may float off the backing paper and would crumple if a brush was used to lift them from the water. The eye dropper is used to add a small amount of settling solution to the water to lower the surface tension and make it easier for the decals to be immersed. 
12. Settling solution - compatible to the decals being applied.

Applying Waterslide Decals

	The very first thing to do is thoroughly clean the work area before starting to apply decals. It is a good idea to have a sheet of card or paper laid on the work space of contrasting colour to the decal sheet so that individual decals are not lost once separated from the sheet. Equipment should be laid out in whatever way is convenient to the modeller and this will depend on whether the person is right or left handed. A good idea is to use a small plastic food box to support the model at a suitable height. A couple of cut outs for the wings and fuselage will ensure a stable platform.  The decals are then individually cut from the backing sheet. The cuticle scissors are used to cut around the individual subject, leaving the carrier film intact.
	The scalpel is then used together with the steel rule to trim the excess carrier film. This is done by pressing firmly on the steel rule to make sure the decal won't move and lightly drawing the blade along the edge to only cut the carrier film and not the backing paper. Several passes may be required.
	To the saucer of water, a few drops of settling solution are added using the eye dropper to reduce the surface tension of the water and allow the decal be easily be immersed. The decal is immersed, holding the backing sheet with the tweezers and sliding the subject into the water before releasing it.
	The immersion time varies with the brand, depending on how soluble are the glues used in making the sheet. Once the decal starts to lift, it can be removed from the water using the tweezers to grasp the backing paper and not the decal. While the decal is soaking, the settling solution should be applied to the model in the place where the decal will rest (more about solutions later).
	If the decal floats off the backing paper, the strip of shiny plastic is used to capture the decal by slipping it underneath the floating decal and gently raising it before transferring the decal to the model. Allow excess water to drain off by placing the subject on a tissue.
	Then dip the decal into the water again, drain the excess and holding the backing paper with the tweezers, place it against the model and float the decal off with the brush.
	Position the decal correctly, leave it for about two minutes.
	Then carefully soak up excess fluid with a clean tissue. Some manufacturers urge the use of several layers of tissue or a piece of foam rubber to gently press the decal against the surface of the model. Be careful! This can be disastrous with some decals cracking, embedding themselves into the tissue or foam, or sticking permanently to the model. After several more minutes, apply a little more settling solution and move on to the next subject.

The settling solution will cause the decal to wrinkle but don't worry about that. This is why an area of carrier film should always be left around the decal. Cutting back to the printed image will allow the ink to crack when the film under it is softened by the settling solution. Having an area of film around the printed area prevents this. By using a settling solution you will be able to draw a thin, high quality decal down over almost any surface. Care should be exercised when applying settling solutions because there are differing formulas and the decals may react violently resulting in their destruction. If you are not sure of your settling solution, cut a subject that you don't need from the sheet and observe its reaction to a few drops of your settling solution. 

When all the decals have been applied, allow them to dry naturally, say overnight. Come back to the model the next day and carefully examine the decals for any bubbles of trapped air or creases caused by irregular surfaces. If there are any, use the sewing needle to pierce the offending bubble or crease and apply a drop of settling solution. Allow the solution to dry and, if necessary, repeat the process until the decal lies flat. When the decals are dry, carefully wash away all traces of glue and settling solution and then dry the model carefully to ensure all lint and dust are removed. The last task is to spray on a coat of flat varnish. Once this is dry the decals will look like they are "painted on". As a last resort the modeller can over-paint areas of the decal where it has been impossible to remove the silvering but this is very difficult to do well because the coats of varnish alter the tone of the paint they cover, making it appear darker.

Applying Dry Transfer Decals

These require a slightly different technique because they are pressure sensitive. Dry transfer decals are made in reverse order to waterslide decals. The backing sheet, which is translucent, has carrier film applied to it and it is onto this that the design is printed. Then a thin film of adhesive is applied over the sheet covering the printed areas as well as the carrier film. When the decal is rubbed, it separates from the backing sheet and sticks to the model surface. A sheet of paper, which does not allow the adhesive to stick, provides protection against accidental dislodgment of the decal.

Individual decals should be carefully cut from the sheet with a pair of cuticle scissors, thus avoiding pressure being applied to the decal. To avoid damage to the model, the decal should be pre-released by placing the carrier sheet on the protective sheet and lightly rubbing the carrier sheet until the tone of decal starts to change as it separates from the carrier sheet. The ideal tool for application is a small, soft plastic spatula, but a biro (if used carefully), or a small piece of soft wood (like a swab stick) can also work. Some of the commercial lettering sheets available include a small application tool which is ideal for this task. The decal is then carefully laid in position against the model and rubbed down onto the model. Once the decal is in position the protective sheet is placed over the decal and it is burnished by rubbing the applicator over the backing sheet. This presses the decal firmly against the surface of the model and allows the adhesive to grip. Extreme care must be taken to make sure the pressure is not great enough to damage the decals or the model. It the decal breaks up during application, it can be re-positioned using tack paper and if this fails it should be removed with masking tape. These decals are very difficult to use successfully and many modellers prefer to apply them to a clear waterslide decal sheet, seal them with a coat of varnish and apply in the conventional way. The last thing to do is spray the model with a coat of matt varnish - but first make sure the varnish is compatible with the dry transfer!

This style of decal has limitations with regard to the shape and finish of the surface to which it can be applied and this should be taken into account during use. With this restriction in mind, excellent results can be achieved.

Settling Solutions

No matter what manufacturers tell you in their publicity notes, the awful truth about settling solutions is this: they are all based on alcohol and all of them soften the decal by attacking it. As an added bonus, some settling solutions include acetic acid in their formulas! Settling solutions have been around for a while and were originally developed for the model train market where the sharply irregular surfaces required something the help decals snuggle down tightly. The strength of settling solutions available on the market varies greatly. The most commonly available brands are Hobsco, Microsol and Microset, and Gunze Sangyo Mr Mark Softener.

Hobsco Decal Settler is designed to be used on model trains and is ideal for getting decals down on sharp, deep, irregular surfaces such as the vortex generators on Skyhawk wings or the camera ports on a Sonia. As this solution is very strong, it is best tested on a spare decal before use.

Microscale's Super Microset and Super Microsol are the original formulas and they were followed by Microset and Microsol. Following the demise of the company, various versions of the product have been produced by the two new companies resulting from the split. These products are a two part system; Microset is applied first, acting as a cleansing and wetting agent. Then, the decal is applied, followed by more Microset. After a few minutes the decal is carefully and very gently pressed home. Then Microsol is applied and allowed to dry. Any blisters are pierced with a needle and more solution is applied. In some cases further applications of Microsol may be needed make the decal conform to the surface of the model.

Mr Mark Softener is slightly different in that it can be used to apply decals directly to a matt surface and it removes all trace of the carrier film by softening to such an extent that it "melts" into the paint. A piece of high density foam is needed to press the decal home, thus avoiding any pattern being imprinted on the decal. This solution may not be compatible with all makes of decal and care should be taken when using it. Models finished with this product are indistinguishable from those prepared in the more conventional manner. This product has the advantage that it is only applied once and does not need to work in combination with a wetting agent.

Making Your Own Decals

If you own a personal computer and are lucky enough to have a laser printer, dry ink printer or an inkjet printer you can produce your own decals using specially manufactured papers. Once printed, handle the decals carefully because the printed image is fragile. It is recommended that you seal the decal with a coat of gloss varnish before using it. Experiment with various varnishing solutions available. Try to choose acrylic base varnishes as these are less likely to eat their way through the printed image, gun or even backing paper. For this application, you will need to look outside the ?modelling? square. A good source of varnish is the local craft store.

Salvaging Old And Faulty Decals

	Quite often one can find that there has been decal sheet created at sometime or another that has a very special place in a person's modelling area of interest. Often the decal file reveals a yellowed example which can be salvaged for use with a bit of patience. The easiest way to get rid of the yellow is to pop the decal into a plastic sleeve and tape this to a north-facing window for a while, checking the decals daily. The sun bleaches out the yellow, without loss of colour and the decals can then be used. Make sure that you remove the decals when the yellow is gone so you avoid fading the printed image.
	Another problem is that the sealing varnish may sometimes be too thin or totally absent and the decals shrivel or shatter into a million pieces on contact with water.
	There is a particular brand of decal that has a reputation for this but even a brand that has a reputation for being high quality can sometimes have a batch that is sub-standard. Some decals can be destroyed by settling solutions. Therefore it is wise to test all decals by sacrificing a small or insignificant decal from the sheet before using it. If the decal is found to be sensitive to the settling solution, it can be saved by spraying several coats of clear gloss varnish over the sheet. A side effect of this is that it may often take the decal a lot longer to separate from the backing sheet. It can also make it thicker and less flexible.

Decals are not the be all and end all of modelling but correct and imaginative use will produce models of great quality. Experimentation and care are the catch-words for this aspect of modelling and, above all else, the modeller should be prepared to insist on using quality decals.