Diamond tools are expensive. You must know how to use and take care of them if you don't want to flush your money down the drain. If not properly taken care of or used, these expensive tools can contract damages that can render them unusable or very inefficient. One type of problem that can happen to diamond tools is called glazing.
So what is glazing?
When heated to extreme temperatures, the binding material that holds together the diamond particles becomes malleable. The now malleable binder can "flow" over the diamond particles, covering and preventing the diamond from making contact with the work piece and removing material off it. In short, glazing blunts diamond tools.
There are three things you can do to prevent glazing. One is to make sure that you are using the correct speed settings for the type of material that you are working on. The correct speed helps prevent the generation of extreme heat which causes glazing.
The second is by being more thoughtful when it comes to material selection. There are materials for which diamond tools shouldn't be used on. Either change the tool or change the material.
Even when used on the right material with the right speed setting, the grinding and cutting actions is still going to generate tremendous amount of heat. This is especially true when the task involves long cutting process. In such cases, it is recommended to use cutting fluid. Cutting fluid is sprayed on the diamond tool and the work piece to regulate heat. This way, the tool can be used longer without worrying about overheating and subsequent glazing.