Methods for dealing with them tend to fall into one of two categories â `` either make the ceramic in the desired shape , by reaction in situ , or by `` forming '' powders into the desired shape , and then sintering to form a solid body . Methods for dealing with them tend to fall into one of two categories - either make the ceramic in the desired shape , by reaction in situ , or by `` forming '' powders into the desired shape , and then sintering to form a solid body .