"Weathering" a model tank or other model armoured fighting vehicle, or AFV, refers to the process of adding the look of wear and tear to the kit to make it appear authentic and battle tested. Various forms of weathering—from snow, sand and mud effects to more mechanical and combat-related damage to kits—are all considered part of the weathering process. Unless you are modelling specifically to show the product as it looked coming off the production line, weathering is an important part of finishing your kits.
Seal your painted tank model with a flat- or satin-finish spray sealant before weathering.
Create a filter, also known as a "wash," by mixing a heavily diluted concoction of 5 per cent oil paint to 95 per cent paint thinner. Earth tones and light greys are favoured colours.
Brush or airbrush the filter over the entire surface of the tank evenly and allow to dry.
Mark scratches on the surface of the tank randomly using coloured pencils that are a shade or two lighter than the colour scheme. Light grey pencils will work well on almost any tank. Make sure the pencils are very sharp and apply lightly.
Add rust-coloured paint with the tip of a small brush along areas most likely to be paint chipped such as wheels, areas where external tools are stored and protruding edges. A silver leaded pencil also may be used for areas where paint has chipped away.
Add the appearance of caked mud by applying irregular globs of modeler's putty or finely mashed papier-mâché and paint when dry. Plaster works well for snow in small quantities.
Take a flat-tip paint brush and dip the tip into a light colour of acrylic paint, preferably the shade of dried mud, sand or dust.
Pull as much of the paint off as possible with a clean rag or paper towel until none is visible, then lightly pull the brush over the surface of the tank. This is called "dry brushing" and will simulate a layer of dust or dirt.
Mix a solution of flat black paint and paint thinner in approximately 50/50 proportions and brush on around the end of the gun barrel to simulate soot from firing. Go heaviest around the mouth but do not overdo it.
Apply a flat sealant coat and allow to fully cure for at least an hour; overnight is recommended.
Mix a solution of 20 per cent black, dark grey or dark rust-coloured oil paint and 80 per cent paint thinner to create a final wash and apply to the entire surface of the tank to get a uniform look and shade the crevices. Dab away pools of excess wash with a clean cotton cloth.
Seal the final product with a flat sealer.
Research your tank before you begin so that you use the proper colour schemes. Washes can be used on more than one project, so it's a good idea to mix them in glass containers with lids. Acrylic paints and water may be used instead of oils and thinners, but oils tend to add more depth. Tank treads are often applied last and may be muddied, rusted and dry brushed separately. Battle damage can be simulated by applying a heated screwdriver or old soldering gun to the armour, but it is best to experiment on scrap plastic first. Plastic parts can be bent or remoulded using a heat gun as well.
Always paint in a well ventilated area. Be careful if you are using hot tips to simulate battle damage and do this in a well ventilated area as it will give off noxious fumes. If you use a heat gun, go slowly. Plastic will reach a critical point and melt away if you are too close or use it too long.