One of the most frequent points of failure during baking measurement conversions is mixing up liquid and dry measuring vessels. While 6 fluid ounces and 3/4 cup of dry flour occupy theoretically equivalent cubic volumes, the tools designed to measure them behave very differently.
Dry measuring cups are designed to be filled to overflowing and planed flat across the rim with a butter knife. They possess flat, straight edges specifically to avoid compacting fine powders. If you attempt to measure 3/4 cup of milk in a nested dry cup, surface tension will bulge the liquid over the top, almost guaranteeing a spill when transferring it to the mixing bowl.
Liquid measuring cups, conversely, use clear glass or plastic pitchers with clear graduated markings well below the pour spout. When checking 6 fluid ounces or 177 ml in a liquid pitcher, set the container on a completely flat surface. Crouch down so your eyes align horizontally with the measurement line. Read the bottom of the curved meniscus, not the liquid crawling up the glass edges, to verify your true 3/4 cup fill.
