I’m in the process of applying decals to several vehicles and thought it was long overdue that I discuss how to do this. Now I’m not an expert by any means, and my experience is limited to the water based ‘slide’ decals that one associates with Airfix Kits (also known as ‘Transfers’) and the type sold by Battlefront for their FOW vehicles. I’ve also bought several other types from other manufacturers but always the water based variety because these are what I am familiar with. Over the years I have encountered several problems when trying to handle and apply these often small and temperamental details. So here’s my troubleshooting guide to applying decals.
Planning the Job
Take a few moments to decide what decals are being applied and where they will be positioned. This is a fiddly job so the more organised you are the easier it will be. You will need several tools before you start, including a sharp knife, tweezers, q-tips, tissue paper, gloss varnish and setting solution (described below). You will also need a shallow bowl - I use a ramekin dish - with warm distilled water.
Prepare the surface
Decals applied directly to a Matt surface can develop a silvery sheen. This is caused by micro bubbles between surface imperfections in the paint and the decal. There are two solutions to this problem. First you could use a Decal-setting solution which softens the decal allowing it to bind more closely to the surface. However setting solutions can cause decals to melt if they are too strong, which could be a problem if you use decals from different manufacturers. The second option, and the one I use, is to use a gloss varnish on the area where the decal is to be applied. Once dry it provides a smooth surface for the decal to adhere to and prevents silvering.
Releasing the Decal
First I cut the individual decal out from the sheet leaving enough backing paper around the decal to hold with tweezers. Soak the decal in WARM water for just 10-15 seconds then take out of the water and wait another 30 seconds. The Adhesive binding the decal to the paper should now have dissolved and the decal can be applied. Soaking too long in cold water runs the risk the decal will separate and end up floating in your water.
Sometimes large visible bubbles can ruin a decal. At the application stage bubbles can usually be brushed away (hold the decal in place with a cotton bud or blunted toothpick then brush the bubble towards the nearest edge). If a bubble is detected on a dry decal the only solution is to pierce the bubble with a pin or knife and smoothing with a damp brush. Weathering (see below) and varnishing can cover up smaller bubbles.
I usually wet the surface before application to make it easier to reposition the decal. Once in position though it is necessary to remove as much excess water as possible and start the drying process allowing the decal to adherer. A dry brush tip can be used to draw off excess water, or for larger areas a dry cotton bud or q-tip. Another option is to use the corner of a piece of tissue paper. Whichever method you use be careful not to touch the decal at this point because it will not have adhered to the surface yet and could be moved.
I have found that decals often vary in quality from one manufacturer to another. Think decals can sometimes crack or split when applied on uneven or curved surfaces. If this happened the modeller has only two options. Either remove and replace the decal before it dries, or paint over the decal filling in the gaps. For simple decals like American Stars or Balkan Crosses this can be quite straightforward but is a nightmare for complex unit insignia.
Deep surface detail
In real life unit or national insignia were often applied across door breaks and engine covers etc. It may be necessary to apply a decal across a deep grove or other large surface detail which can use creases or bubbles. The best solution is to use a sharp knife to score the decal once it is in place. The knife needs to be sharp because the last thing you want is to move the decal as you drag a blunt blade through it. Apply a small amount of setting solution to ‘melt’ the decal into the grove or around a bolt etc.
Some decals have more adhesive biding them to the backing paper than others. Sometimes this adhesive is not entirely dissolved when the decal is applied and creates a ‘stain’ on the model surface. These can usually be removed by wiping the area with a wet brush or q-tip but again, be careful not to touch the decal and accidentally move or damage it.
Seal in Place
I always varnish my models to make them durable when handling but even if you don’t do this you should consider applying a gloss varnish over the decal. This softens the raised edges and blends them into the paint job. Additional weather can be added over the top of this coat to further blend the decal into the model. Finally I apply Testors Dulcoat over the whole model to create a uniform surface.
I hope you've found this guide useful, and of course if you have any other suggestions or tips I'd love to hear them (this dog likes to learn new tricks). There are also several other guides online that you can refer to such as the Flames of War guide to Decals and Doctor Faust's Painting Clinic.