Is the transparency of ice formed from distilled water greater than that formed from tap water? That is the question. Here are some photos of one process involving three samples of water. The apparatus: Three medium watch glasses, tap water, distilled water, graph paper grid, cardboard stand to hold the ice and the freezer compartment of a lab refrigerator. Procedure: The samples of water were poured up to the rim of the watch glasses sitting on the freezer shelf. The first watch glass received tap water. Southern California tap water contains 100-200 ppm total dissolved solids. The second watch glass received distilled water aerated by shaking 100 mL in a 500 mL graduated cylinder. The third watch glass received hot distilled water boiled for two minutes.



The setup is shown in the image at the left. Each sample in turn was removed from the freezer and the back of the watch glass warmed with cold tap water and set in a cardboard holder in front of a grid. As you can see, the tap water sample at the right is opaque.















The photo on the right shows the aerated distilled water and the one on the left shows that which was boiled and poured into the watch glass while still hot. Both of these show some transparency, though one could argue with more than a little ambivalance, that the boiled distilled water is a bit more transparent.