Oops, I’m reading your post (ATA 142), and I think you misunderstood the question: it’s not a problem. It’s a GOOOOOOD thing that it’s thickening. This recipe results in beautiful magically thick and velvety drinking chocolate. The question is why?

What exactly is thickening it? I want to make sure I understand what’s happening so that when I instruct others to make their drinking chocolate this way I understand what the potential failures are.

I did indeed misunderstand the question. Seems like that pattern that has been established that I fell into is that people write with problems and not pure ‘why’ questions. I did what dislike. I read between the lines – and did it poorly. Which is why I really try and not to do it.

So, why?

The short not helpful answer is that you are creating an emulsion. In layman’s terms this means that the water molecules are being surrounded by fat molecules. When this happens that water can’t act like water. It acts more like a solid. Hence thickness. With enough water, it can also go the other way. Water can surround fat molecules and the result is similar. That flowing warm chocolate stops flowing and gets more solid like because the everything is trying to stick together on a molecular level.

And it gets even more complicated. In neither of those cases does it explain why just a small amount of water causes chocolate to get thick, i.e. seize. In effect it the non-water and non-fat (i.e. cocoa solids) parts of the chocolate are absorbing the water. Sort of like a sponge. And the particles swell up. This basically clogs up the system. It’s harder for things to move around. Think of a pile of sand vs a pile of rocks. Which pour easier? The sand, right? Once the water goes in, the ‘sand’ swells up into ‘rocks’ and they don’t pour, or move easily.

This rather leads to why I thought this question was a problem. Because I’ve thought of it as a problem. When I have made drinking chocolate I’ve found it very difficult (impossible) to make an stable liquid one that isn’t too thick or that doesn’t become too thick over time. At somewhere around a 1:1 mixture of chocolate and water it is pretty smooth….but if you wait a little while it thickens up to the point you can’t drink it. If you add more water so it is now 1:2 chocolate to water the same thing happens. It’s smooth and flowing…and then thickens up some time (15-30 minutes?) later. I’ve done this over and over up to something like 1:10 or 1:15. Each time you add water, the cocoa solid sponges start soaking up more water, but it takes time. This is what I thought was being asked about. “Why is my drinking chocolate getting TOO thick?”

So, there. I hope that clarifies a little. The drinking chocolate is getting thick for three reasons. Two types of emulsions (water/oil and oil/water) and what I am calling the sponge effect. Mostly it is the two emulsion, but some is sponge and if you break the emulsions it goes to full blown sponge.  And generally speaking, emulsions tend to be 'velvety' and when they break the mixture gets a bit more clumpy and loses some of it's sheen.