Students from a nationally registered dietitian course assessed the viscosity properties of thickener solutions. This panel of students adjusted the viscosity of the thickener solutions using thickening agents and attempted to achieve viscosities similar to those of ketchup, pork cutlet sauce, and potage. The apparent viscosities of the thickener solutions prepared using 7 kinds of commercial thickening agents were compared with the apparent viscosities of 28 kinds of real foods. The spreading coefficient of each thickener solution was determined using the glass ring method, and the amount of water used for preparing each thickener solution was controlled. Variability was observed among the panel in the assessment of viscosity properties of all the samples;the viscosity of ketchup, a standard high-viscosity solution, tended to be over-adjusted to lower than it should have been by the panel. In addition, variability was seen in the apparent viscosity of several actual foods in each product type. Although the same food index was used during preparation, the apparent viscosities were different for most thickener solutions. The thickener solutions adjusted to have the same viscosity as mayonnaise were prepared with a small amount of water and showed a lower expansion factor than mayonnaise sample prepared using larger amounts of water.