There are several ways of softening an edge. When I present them in this post,you will probably say to yourself. "Whats the difference whether I use one or the other, it looks like the end result is the same?"
Here in the lab there isn't a lot of difference, but I will be going somewhere with this later. I am laying ground work for some further conclusions.
Okay, here is our first example. The edge between the two notes has been made by pulling a flat bristle brush along the edge. That melds the two together. If I was doing real slick work, I might want to use a sable for this. But In my brushy paintings a bristle is just fine.
Also, as an aside here, notice my handling in the blue portion . That sort of fat look to the paint is something I have learned to do. Often painters try to push the paint around with lots of medium and not enough paint. I make em out of paint . I am a brushwork guy and often I want that luscious look of the full bodied paint. You may want that, or not want it, but you should be able to do it. It is another arrow to have in your quiver when the need arises.
To do this, you load the brush (bristle ) and put the paint down straight no medium, and then most importantly you leave it alone. Try working with your paint as it comes out of the tube with no added turpentine or medium at all. I 'll bet you get the best handling you have ever had in your life. If you need to speed your drying add a little alkyd to your white before you begin, but don't put it on your palette. This is not always how I do things but it is something I use to get a certain look out of the paint. Incidentally if you are putting pea sized blobs of paint on your palette, you will never have good handling.You may get an enameled surface, but you won't have expressive brushwork.
You are working on what Emile Gruppe called a starved palette. He said to paint like a millionaire. Squirt more than you would put on your toothbrush, onto your palette. Get cheap somewhere else, buy the generic soda. Teach your pets to forage for themselves. But lay out enough paint to allow you to use it freely. I am always amazed by how stingy students palettes are at workshops. When I lay out their palette with enough paint they act like I am crazy. Then they drive home in a Mercerdes.
Here is the other way of dealing with an edge. I am referring to this as softening it, but actually this is something different. Rather than blurring the two together I am darkening the light note as it approaches the dark note, and I am lightening the dark note as it nears the light note.
I am really downplaying the value shift between the two. The viewers eye will pass on without "over registering:" on the edge.
This means of dealing with an edge allows all sorts of trickery and diversions in the designing of paintings. More about that in a following post.
The second way of making edges often gives a firmer look to your work. Too many softened edges that are pulled together can give an overly slick look to a painting. Making your edges by adjusting your values is often the better choice in practice.
I suggest you practice until you have both in you repertoire. You need to be able to blur or pull delicate colors together without dirtying the notes , only melding them. To do the values control method you will have to think about altering the temperature of the two notes as they come together. Sometimes that is not necessary, but sometimes it is. You should be able to do both neatly and cleanly. I have seen many still lives and many horizons in landscapes ruined by crudely handled edges.