For this demonstration I worked on the same painting for many rounds in a short period of time. That is why I chose acrylics because it dries fast and you can see all the differences.
What is a glaze?
It is when you use a painting medium of choice with pigment to do a wash across a painted surface. Do not use white because it is opaque. For example: you might use Professional Walnut Oil for glazing with oils or use acrylic matt medium for glazing with acrylics. The choice of medium is determined by the way in which you like to move paint, change it’s viscosity and like the finished look of. There are so many to choose from. In the demo I used Acrylic Matt Medium, Acrylic Gloss Medium, Gloss gel and varnish.
Why do a Glaze?
It can add a color to an area that is subtle and you don’t have to go about repainting that whole area, it can soften edges and doing a lot of layers, it can defuse colors and create a more atmospheric look.
When to do a Glaze?
When you want to change a large and general and it would be more efficient to do it with a glaze, or you are just about finished and just need to do a subtle change, or you want your piece to feel more atmospheric, soft and have more depth – yes it creates more a sense of depth. You can do it at the end or throughout.
When glazing the surface should be dry, which means for acrylics you can go ahead relatively soon, same day. But with oils, you might have to wait almost a week for thorough drying. And with oils you must make sure your layer underneath the glaze is thinner in texture and the fat content is thinner then what you are putting on top, otherwise you will end up with cracking. You can look this up on Ralf Mayor’s Materials and Techniques. This is the artist bible for materials information.
You can see in my demo how subtle some changes are and then I got feisty and put too much pigment in and really changed it. But it certainly changes the look and the feel of the paint.
Hope I answered some questions.