Probably one of the most versatile and widely used basic weathering techniques in model railroading is using what is called an “India Ink & Alcohol” wash on your structures. It can be used on wood, plastic, metal castings (after primed and painted), hydrocal castings and other materials.
Depending on its strength (discussed in detail below), it can give an appearance of aging or even dull the new ‘sheen’ of injection moldings. It can often bring out the hidden details or add more realism to your models.
There are two main ingredients: Isopropyl Alcohol and India ink. Isopropyl Alcohol, commonly known as ‘rubbing alcohol’ can be found at most drug stores and some hobby shops. It is generally found in the following strengths: 70%, 91%, and 99%, whereas the number is the amount of alcohol to water (i.e. 70% contains 30% water, whereas 91% contains 9% water). 99% is a little harder to find and costs more than the other two.
Most model railroader’s use 91% formulation, as water is a natural enemy to wood structures and the less water involved, the less chance of warping and the faster the evaporation. That being said, some people say the 91% formulation can act as a paint stripper, but personally I haven’t run into that as an issue, even when using acrylic (water based) paints. Then again, I’m using very fast brush strokes, and a subtle amount of the wash. I could see there may be a ‘stripping’ problem if one used a lot of the wash and pressed hard in a certain painted area.
A pint of Isopropyl Alcohol runs approx. $2.00 – $2.50 and can last you quite a while as long as you replace the cap tightly after use.
India ink (Higgins is probably the most popular brand, but not the only), on the other hand can be found in office supply stores, art stores, and craft stores. It’s usually sold in 1oz containers with a dropper built into the top and runs anywhere from $4 – $5. It’s pretty powerful stuff and is generally fade resistant and also waterproof. You’ll want to be careful and not spill this on good linens or anything else you don’t want permanently stained.
Now onto the recipe: Many modelers have 2 prepared wash mixes available when modeling; a light mix, and a heavy mix depending on their application. I personally have only used a ‘light’mix in my modeling thus far and am very happy with the results. Mix 1 Tablespoon of ink to a whole pint (bottle) of alcohol and shake. A heavy mix would be at least 2 Tablespoons to a pint. Yes, the ink is that powerful… a little goes a long way.
Use a cheap, soft bristle brush when applying a coat of your wash to a surface. I’d also keep that brush separate from all others and rinse out thoroughly when you can.
Go ahead and apply a quick stroke to the surface you wish to ‘weather’. Don’t be alarmed if it looks overly dark at first (I suggest testing on some scrap material at first if you’re wary). It will lighten up slightly as the alcohol dries and evaporates.
That’s one of the reason I use the ‘light’ mixture. If it looks like it needs more, I can always add a second coat, but I can’t reverse from a heavy coat to a lighter one.
Here is a great article and example of weathering wood