How to optimise the performance of your Findenser

Author: Carly Hammond
Date: Aug 20, 2018

W8 - Findenser

Findenser is revolutionising refluxing in laboratories around the world.

Traditionally, water-cooled condensers are used, but chemists have to ensure they’re close to a suitable water source and drain. The tubes can get in the way, and what’s worse, they can even pop off and flood the lab. The use of running water is also a tremendous waste of a precious resource – and money. The alternative was standard air-cooled condensers, but often they don’t condense well enough.

The Findenser is the best of both worlds. This innovative air condenser is specially designed to have a very high surface area, so it can perform as well as water-cooled condensers in the majority of reflux applications.

If you’re using a Findenser, but unexpectedly you’re experiencing significant solvent loss, then the cause is likely to be one or more of the factors below. Our top tips will help you to resolve the issue and get the maximum performance from your Findenser.

Too much solvent

If your round bottom flask is too large or is over-filled, the condensation load on the Findenser could exceed its ability to cool and condense effectively, so Findenser may not be able to contain all the solvent.

Ensure your flask volume is appropriate for your Findenser. The maximum recommended round bottom flask and solvent volume for use with each type of Findenser is:

  • Standard (full-length) Findenser: maximum flask size 2 L, with maximum solvent volume 1 L.
  • Findenser Mini: maximum flask size 250 ml, with maximum solvent volume 125 ml.

Solvent volumes should always be a maximum of half the flask volume, e.g. 25 ml in a 50 ml flask, or 500 ml in a 1 L flask. This is standard good laboratory practice.

Overheating or poorly regulated heating

If you overheat the solvent, you can’t get hotter than the solvent boiling point, and you’ll just generate more vapour, which could be beyond Findenser’s capacity to condense.

The hotplate or block temperature should be set to no more than 20 °C above the solvent boiling point for high boiling point solvents (> 80 °C), or 10 °C above the boiling point for lower boiling point solvents (< 80 °C).

Where an oil bath is used, the hotplate or oil bath temperature should be set to no more than 10 °C above the boiling point for high boiling point solvents (> 80 °C), or no more than 5 °C above the boiling point for lower boiling point solvents (< 80 °C).

Please take extra care if the heating control is not fully calibrated, or does not have precise settings.

Inert gas flow encouraging evaporation

A flow of inert gas (e.g. nitrogen) through the flask can encourage evaporation and reduce the performance of the Findenser.

If inert gas is required, it should be introduced through the top joint of the Findenser, with all flask ports sealed (using a suitable bubbler to avoid a build-up of pressure) and not through a flask sidearm or joint at the bottom of the Findenser. Gas flow should be kept to a minimum.

Ambient temperature too similar to solvent boiling point temperature

Findenser uses air to cool and dissipate heat, so it requires the ambient air temperature (room temperature) to be significantly cooler than the boiling point temperature.

At relatively high ambient temperatures, there may be insufficient air cooling for the heat from the Findenser fins to be effectively dissipated, which could result in Findenser not containing the solvent.

The performance in each application will depend on how different the ambient air temperature is from the solvent boiling point temperature, so there should not be a problem with condensing high boiling point solvents.

To maximise performance, keep the lab cool if possible, and ensure there is sufficient airflow around the Findenser to enable effective heat dissipation.

Very low boiling point solvent, e.g. diethyl ether

Some very low boiling solvents are particularly tricky to condense due to the small temperature difference between the vapour and the ambient temperature.

Findenser can cope with small volumes of diethyl ether (up to 100 ml in a 250 ml flask) with a hotplate / heating block accurately controlled at no more than 5 °C above the boiling point, in an air-conditioned lab.

For larger solvent volumes, or warmer lab temperatures, a water-cooled condenser may be the only option. Save your Findenser for use in other applications.


Armed with this information, you should be able to get the best out of your Findenser.  If you need any further advice, please feel free to email the Technical Support team at, and we’ll be happy to help. 

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