Randy, >>>You don't want to keep oxalic sugar water solution for more than a few days even in refrigeration. >What data do you base this recommendation on? The study cited by Dave indicates that the refrigerated solution would not degrade to HMF almost indefinitely. I guess I need to backtrack. :) I do recall reading that oxalic acid solution should not be kept too long even in refrigeration. However, the Swiss lab has looked into it and their work showed that, stored at 4C or colder, there will be a maximum of 22mg of HMF per kg of solution beyond some 48 weeks of storage. http://www.culturaapicola.com.ar/apuntes/sanidad/varroa/acido_oxalico_ rago_jarabe.pdf Since this may be a safe level to the bees, it appears you can keep OA solution at =< 4C short term. I treat once a year and I can treat all my hives in one day, it does not make sense to try to keep OA solution to the following year. Thanks. Waldemar *********************************************************************************** * Full guidelines for BEE-L posting are at: * * http://www.honeybeeworld.com/bee-l/guidelines.htm * ***********************************************************************************