Ok, no need for sarcasm. Gum arabic is a watercolour medium that I assumed would make for a more glazed tile-like look. This turns out to be sort-of true.
Obviously this glossy look does not come through in my terrible cameraphone photos but it is glossy. The green-gold ones actually have gold ink underneath. That also kind of works. Ignore the bad colour choices on this one, that’s not the point.
Well it would be nice to try multiple layers of colour, to see what effects you can get. I also bought some aquapasto at the same time, to see what that would do. It should thicken the paint but seems to just reduce the intensity of the colour (the hue?). The guy in the shop was very enthusiastic (shout out to London Graphics Centre - which is very full of interesting stuff). However not quite what I wanted. Gesso actually seems to work for thickening - but again not ideal.