system
Given the following post, respond as if you're commenting on Reddit:
human
What type of porcelain glaze reduces surface tension?

What type of porcelain reduces surface tension of water?

The best surface to mix watercolors is a porcelain glaze. When mixing watercolor, you want a palette surface where the water will spread out and stay where it's wiped from the brush, not bead up. Essentially, if you wipe a wet brush on the mixing surface, the water should streak out as a solid ribbon of water and not bead up and break. 

When testing porcelain tile at home depot, I found that all of the bath tile caused the water to bead up to some degree. But, when I use a basic dinner plate, the water spreads out evenly without beading.

I am wondering why a glazed surface like a dinner plate would work fine, but a bath tile would not?
gpt
You're dealing with an extremely complicated set of physics: Wetting and contact angles.

There are no easy generalizations that can be made. ***Any blanket statements made about this  topic will ALWAYS have exceptions***. There is ***only*** a set of equations that can be used to calculate the wettability of a specific material, with a specific fluid.

Every fluid will behave differently. Every surface will behave differently.

Glass CAN make water bead on its surface. It can also make it wet the surface. Porcelain CAN make water bead on its surface. It can also make it wet the surface. Even intuitively absorbent materials, like a sponge, or fabric, can make a fluid bead up. We've all had clothing that spills will bead on, until we move the slightest bit, and its absorbs. Conversely, intuitively "slick" surfaces like a car's paint, or a piece of polished metal, can be wetted. 

This phenomenon is not a simple matter of surface tension, even though surface tension is one variable in the set of equations that govern it. There are many other factors: what is the composition of the ***air*** surrounding you? What is the chemical composition of the pigments you have dissolved in the water?

All you can do is test different materials, to find which ones work best for you. Trying to predict this is essentially impossible.