The Heavier Plate Investigation


Before -- The dish on the right was noticed to be strangely blotchy looking after a round in the dishwasher, and on closer inspection, was found to be covered in a network of little cracks. The dish was also felt (literally) to be subtlety heavier than a typical dish of the same design and manufacture, shown on the left. Although the original source of the damage to the dish was not identified, it was speculated that it had somehow become 'water-logged'. The weight of the good dish was measured and found to be about 183.6 g, while the damaged dish was found to be about 207.4 g, which is 23.8 g or about 13% heavier. (It is assumed the good dish is representative of the weight of any other good dish, and no attempt was made to find the variability among other good dishes.) In an effort to study any change in water content, the dishes were first measured over a day or two to see if they changed on there own. No change was measured, however it was noticed that the blotches on the damaged dish seemed to spread out, making the entire surface seem more homogeneously discoloured; although nothing left the dish, it was becoming evenly soaked. (Also, the dishes seemed fairly similar to the touch.)


After -- The dishes were both placed in an oven and heated and held at about 270 F. (Actually, the oven was set to 250F, but the thermocouple, in the photo, said otherwise; not that unexpected a result for an oven really.) Initially it was planned to place the dishes in the sun and wind, which should also have done a good job, and been considerably gentler, but such a technique would be far to slow for the project schedule to be met.

After about an hour of heating, it appeared (through the oven window) that there was beading on the surface of the damaged dish (on the right in the photo). Suspecting (suspicious as it was) that the air in the oven was somehow saturated or something, the oven door was left open by a few inches, while the oven continued to run. After another hour, the oven was turned off and the dishes removed, and the above photo was taken.


The damaged dish was covered in liquid, while the good dish appeared normal. While the dishes were still hot, a cloth was used to soak up the liquid, which turned out to be oily. This pretty much explained why there was anything still visible at all, given the oven temperature. Anyway, after wiping as well as possible, the dishes were allowed to cool, and then weighed again. The weight of the good dish was unchanged at 183.6 g, however the weight of the damaged dish had reduced by about 2.9 g, to about 204.5 g, such that it was now only about 11.4% heavier than the good dish. Finally, after a few more days, the dishes were weighed again and found to be unchanged from these levels. It is noted that although the damaged dish seems to remain well soaked with oil, it does not feel much different to the touch (on the surface) from the good dish. (Turns out the damaged dish sat for weeks with butter on it, prior to being sent through the dishwasher.)