A couple weeks back I reported on the work of Richard Newell, who sealed boiling water in mason jars in a canning system and found that it made great ice with few bubbles in a directional freezing system.
I don't have a canning system but I thought I'd give it a try with what I had around the house. It turns out I had a big jug, so I used that as my mason jar.
I boiled water for quite a while inside the jar inside a pot, and then went to screw on the cap of the jug - only to find that I didn't have a cap that fits the jug :(
So instead I transferred it to glass bottles for which I have plastic corks. As you can see, I filled these up all the way to the top before capping them.
I put the glass bottles in the freezer to cool down before transferring them to my cooler for directional freezing. As you can see, after chilling there is a lot more space in the bottle.
We know that hot water holds less air than cold water, so was this extra headspace the water reabsorbing air (meaning my corks weren't airtight) or that it pulled a vacuum as the water cooled? I'm not sure.
I poured the bottles into the cooler and froze it. Unfortunately, it did not appear that using boiled water "sealed" in bottles made for clearer ice than usual via directional freezing. It looks to be about 25% cloudy ice, which is normal.
I might have to try actual mason jars and seal them as Newell did initially to know if sealing up boiled water improves clarity in ice.