Is it compulsory to use glazing material to glaze the ceramic?

The glaze firing can be performed without the use of Glaze materials. Although, the advantage of using Glaze materials is that the technician can control the desired level of glaze in a restoration and can be achieved more efficiently.

The difference in the final look that a natural glaze of the fired ceramic has, is a more satiny gloss, whereas the use of glaze materials can result in higher gloss effects.