Starch, aspen fiber and magnesium stearate were first mixed using a Kitchen Aid mixer with a wire wisk attachment. Magnesium stearate acts as a mold release agent, preventing sticking of starch to the mold. For batters containing no PVOH, guar gum (1% by weight of starch) was also added to prevent settling of the starch. PVOH solution (10% by weight, heated to 90 °C for 1 h) and/or water and other liquid reagents were then added so as to give the desired level of PVOH and a total solid content of 33%. Other compounds (see Section 2.1) were added to the batter at 1–2% levels based on starch weights. Acetic acid was added to batters containing the Curez or Melrex resins to decrease the pH to nearly 5. Mixing was continued for 20–30 min. Starch foam trays were prepared using a laboratory model-baking machine (model LB TRO) supplied by Franz Haas Machinery of America, Richmond, VA. This equipment consists of two heated steel molds, the top of which can be hydraulically lowered to mate with the bottom half for a set amount of time. Dimensions of the mold were 217 mm long, 134 mm wide, 19 mm deep and 3 mm (plate separation). Baking temperatures were set at 200–205 °C. Actual temperatures at the mold surface were about 10 °C lower as measured using a Temp-Sure Digital Pyrometer TS-200 (D-M-E Co., Madison Heights, MI). Baking times were the minimum required to avoid a soft or bubbled tray and varied from about 80–140 s.