What is the optimum volume of solvent to be used in a flask with Findenser? It is standard ‘good practice’ when heating solvents for a maximum of half the flask volume, e.g. 50 ml in a 100 ml flask, 1 litre in a 2 litre flask, to be used. If a flask is over-filled, the condensation load on the Findenser may exceed its ability to cool and condense effectively. In such circumstances Findenser will not contain the solvent.