It is difficult to draw a line between what is matte and what is semi-matte (also known as soft matte) from a visual inspection point of view. However from a production point of view it is much easier. Glazes generally want to be glossy, the vast majority of random glaze formulations would be glossy. Matte glazes, on the other hand, are difficult to create, there is a narrow range of chemistries wherein matte effects will develop such that the glaze is still well melted and does not cutlery mark or craze. Matte glazes can be such because of a micro-rippled light-scattering surface, because of crystallization or because of phase changes that scatter light, each mechanism has its own firing and process challenges to maintain. Companies generally configure their process to make the glaze as matte as possible while still having good technical properties (actually some do relax the technical properties and tolerate some cutlery marking, for example). A semi-matte is a relaxing of the stringent requirements of the matte effect, a movement toward an easier-to-manufacture, but glossier product (as opposed to stony mattes which compromise functionality for even more matteness). The semi-matte space is quite volatile, small chemistry changes can produce large shifts in gloss of the fired glaze. Companies can measure the amount of semi-matteness by measuring the amount of reflected light from a glaze surface or comparison of surface micrographs.
How to matte Ravenscrag Slip at cone 10 by adding talc
2,5,10,15% talc added to Ravenscrag Slip on a buff stoneware fired at cone 10R. Matting begins at 10%. By Kat Valenzuela.
2, 5, 10, 15% dolomite added to Ravenscrag Slip at cone 10R
This is a buff stoneware clay. Crystal development toward a dolomite matte begins at 15%. By Kat Valenzuela.
Out Bound Links
In Bound Links