Solutions to Rotary Evaporator Bump or Foam

Rotary evaporator, also called rotary evaporating machine, is a commonly used equipment in laboratories, which consists of motor, distillation flask, heating pot, condenser, etc. It is mainly used for continuous distillation of volatile solvents under reduced pressure, and is widely used in fields such as chemistry, chemical engineering and bio-medicine. Why does the rotary evaporator appear foaming and bumping during use? Is there any effective solution?
 
When the sample is heated rapidly, it will boil, which creates bubbles and causes the concentrated sample to splash out of the flask. Generally, it is because the heating speed is too fast or the applied vacuum is too high. If the evaporating flask is more than half full, it will increase the chance of damage and splashing into the rotary evaporator. Therefore,  slow down, start with a low vacuum, carefully observe the sample, and reduce the pressure to avoid collisions. It is the same with the temperature of the water bath. Don't make it overheated at the beginning, and carefully observe the state of the sample while heating slowly.
 
Although it is generally possible to be very careful to prevent collisions, it is very difficult to avoid foaming completely. Because there are surfactants in the sample, foam will be generated. We can apply vacuum slowly, observe the sample carefully, and release the vacuum when foam occurs by opening and closing the stop cock to make the foam smaller.
 
Some measures can be taken to help resolve the bumps and foam that may occur even with preventive measures. For example, add defoamer to prevent foam, use a larger flask to ensure that the reagent foam such as foam chips stays in the evaporation flask. For the problem of bump in the stirring process, boiling water can be added to make the boiling more uniform.
 
In order to prevent collision or foam from causing contamination and sample loss, a collision trap or foam brake can be installed. This secondary flask can collect samples when the sample is bumping or foaming, avoiding product loss and contamination to the rotary evaporator. Now the more advanced rotary evaporator is available, and the sensor can monitor the vapor pressure and slowly adjust the vacuum, and can automatically deal with bumps and foam without any effort.