Subject: Why didn't my starch-iodine reaction occur properly?

Recently, I performed a starch-iodine clock reaction with a class of 
students. The temperature dependence of the reaction was somewhat 
awry: the reaction at about 0 degrees occurred almost immediately, 
room temperature took a little longer, and the heated reaction took 
several minutes. All reactants were equilibrated at the appropriate 
temperature prior to the reactions, and reactants were mixed in the 
same order each time. Can you suggest any reasons why the results were 
skewed?

Re: Why didn't my starch-iodine reaction occur properly?