Left: Plainsman M390. Right M370 porcelain. The bottom two samples are a popular ultra clear commercial bottled glaze that costs about $13/pint. On the porcelain, it is crazing. On the red clay it is saturating with micro-bubbles and going totally cloudy and even a satin surface (it should be like the transparent above it). It is likely very high in boron and melting too early. Whose fault is this? No ones. This glaze is simply not compatible with these two bodies.
Hobbyists and increasing numbers of potters use commercial paint-on glazes. It's convenient, there are lots of visual effects. But there are also issues compared to making your own.
Clouding in Transparent Glazes