Stains added to a base glaze can change its melt fluidity. Adjust the base.
At the top is a melt-flowGBMF test ball of a cone 6 satin matte glaze, G2934.
Left bottom: 8% 6213 Mason Hemlock green stain added. The color is good but it is not melting as much and the surface is more matte. A solution is to adjust the base: employ a 90:10 or 80:20 matte:glossy blend to give it better fluidity. Right bottom: 8% 6385 Mason Pansy Purple stain added. The percentage of stain appears to be a little low and its surface is a little too matte. Again, blend a some glossy clear in the the matte base to shine it up a little.