Kilns are of the hobby type or home-built. Firing is often too fast and lacks consistency from firing to firing. Glaze recipes have been gleaned from books and other potters and have been put into production on the merits of their visual properties only. Glaze recipes are often leachable and contain toxic metal oxides that can be released. Production facilities lack space and drying is thus 'hurried' and drier facilities are not only not available but their true value is not appreciated.
Potters are often untrained in technical areas of production.
It is very common for people to overestimate their ability to produce both quality and quantity of a given line of ware. Potteries stretched to the limit are on the 'edge of control' already and are ill-equipped to deal with unexpected problems and often unable to diagnose the true cause. Some think that the pottery and ceramic slip-casting businesses are similar. But they are not. In the ceramic shops everyone uses the same clay body, the same slip recipe, the same jars of glaze, the same temperature, the same kilns.