After working on improving part of the gubbins of Canon Image Gateway for most of the day, I reached the point where I'd completed a milestone and needed a break. Around the same time Léon had hit a good break point, and decided to siphon off some of his chocolate supplies to make more chocolate shapes with Katrien's "chocofun" chocolate mold set. He came out from the kitchen to show me that actually pure Green & Blacks when melted properly was really quite runny. After filling the molds with molten chocolate he had some left, so on a whim I poured it into the funnel of prototype chocolate print head. (Which has been rebuilt since that picture yesterday to be leaner and meaner). So we were ready to go.
Also working in our favour, today I remembered to bring in the freezer coolpack thing that I forgot yesterday morning, and had put it in the freezer compartment of the office fridge to chill. So now we had the print head primed, and a nice cold object to print onto to help the chocolate set quicky.
And it just worked! Somehow, the properly melted Green & Blacks is perfect. Two turns of the pump and it forms a small drop. Pause for about a second and the drop falls straight down from the head, and makes a nice 5mm diameter pixel. This was much smaller than I expected we'd be able to make. The coolpack thing helps enormously - the chocolate blobs solidify within a minute or two. We experimented with printing on top of existing pixels (3D here we come) but our aim isn't that good yet. We need James to finish his Lego X/Y mechanism. My original plan was to surround the print head mechanism in a water bath kept above chocolate melting temperature, and I'd assumed that without this the chocolate in the prototype print head would cool and solidify, gunking up the head. Yet we managed to just keep on printing (well, making little chocolate pats on the target) - the chocolate kept its heat and we exhausted the supply in the entire funnel. It seems that we could keep going indefinately by resupplying the funnel with newly melted chocolate.
And as the input is pure Green & Black's 72% cocoa organic chocolate, the output from the device tastes great. The turds from yesterday are history.
Update: Katrien put her pictures online