|Monthly Tech-Tip |
I used a mix 95:5 water:gum solution when making this glaze. But even that small amount of CMC gum slowed down absorption into the bisque (and drying speed) enough that it was impossible to get it on thick enough. The version of the glaze used for the mug on the left has no gum, it is a thixotropic slurry of 1.45 specific gravity. A 3-4 second dip of a bisque piece is enough to build up a good thickness, which is important for this glaze. It dries for handling in less than 10 seconds. The one on the right was dipped twice for about 8 seconds each time and it took a minute or so before it could be handled. Yet it is still much too thinly applied. This glaze needs at least some gum because it is crawling slightly, it is an example of where precision is needed to determine the maximum that can be tolerated without impacting application thickness.
CMC gum is indispensable for many types of ceramic glazes. It is a glue and is mainly used to slow drying and improve adhesion and dry hardness.