The glaze in this jar was 'goop', impossible to paint on. I did not know whether I needed to add water or try to deflocculate it (although the former is more likely and in keeping with what Laguna says on its website). I measured the specific gravity, it was 1.7, so clearly it needed water. It took 125cc to bring the specific gravity down to 1.5. However, it was still thick and dried immediately after painting on, clearly it does not contain enough gum for brushing. The next time I will add a mix of 50:50 gum solution and water for better paintability. The bright side: I got considerably more than a pint after adding the water, a big difference from some other commercial glazes which are mostly water.
In ceramics, the specific gravity of casting slurries and glazes tells us their water-to-solids. Body slurries especially require tight control of this property for performance reasons.
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.