Blending is great! Learning how to blend was probably the most important step in my mini paining career.
But what does blending mean? My definition of blending: "A gradual transition from one colour to another". Imagine a sunrise. Remember how the colour changes from red to yellow without any abrupt transitions? That is blending for me.
When painting miniatures, blending is extremely useful because we create artificial shadows on the miniatures. Look at this picture (ignore the pretty cat please):
The shadows on the purple blanket are very dark, while the raised areas are quite light. Because minis are so small, the light doesn't give this effect on them, and because of that, we have to create the shading effects our selves. But as you can see on the picture, the shadows have to blend into the other colours to create a believable effect. And this is where blending becomes relevant.
Wet blending is a technique often used in oil painting. The principle is to place two colours (that are still wet) next to each other and mix the paint ON the model.
These sketches illustrates the principle:
The two colours are placed next to each other on the figure.
Start mixing the colours to create a smooth blend.
When you are done, you should have a gradual change in colour without any abrupt transitions. When wet blending I always use some kind of extender or retarder to make the paint dry slower. Without those, wet blending is almost impossible.
I'll start by making this even more confusing: You can use layering without using blending. The imperial preacher here is an example:
The highlights on his pretty green dress have been created by using layers of lighter and lighter colours (layering), but the transitions are quite abrupt (so it's not blending). To avoid the ugly sharp transitions you need to use thin paint. So thin that when you apply a layer of paint, it shouldn't be possible to see where the old colour ends and the new begins. The sword of this Eldar Warlock is an example of what it looks like when you blend the colours:
The sketches illustrate the layering process:
The first layer of dilluted paint is applied.
And another layer....
Several layers later. In the sketches the transitions are visible. I just did that to illustrate the technique. The result of the process should look like this:
A really important aspect of this technique (which people often forget to mention, grrrr) is the amount of paint on the brush. When working with thinned paints, there should be very little paint on the brush. If you load the brush with lots of paint, you wont be able to control the flow and you wont be able to create a good blend.
Another important thing is to realize that this takes time, especially in the beginning. As you get used to the process, you will learn a few short cuts which will make you life easier, but it's better to find out for yourself after you've mastered the original technique. I once read an article by Jason Richards and he wrote that if you want to create a super smooth blend, your paint should be so thin, and there should be so little paint on your brush, that when your brush is at the end of the brush stroke, the paint at the beginning of the brush stroke should be dry. I have tried it and it really does look cool, but it takes ages!
Good luck with your blending projects :)