How to Defrost a Manual Defrost Freezer

By Aimee O'Driscoll, 08 June 2018

Defrosting a freezer can be a dreaded task in many labs. But if you have a manual defrost freezer, then it’s a job that needs to be done. Buildup of ice inside the freezer can insulate the walls and make the machine run less efficiently. Plus, defrosting provides a good opportunity to clean out those forgotten samples lurking at the back of the freezer and can help you stay organized.

The frequency with which your freezer needs to be defrosted will depend on various factors, including how often the door is opened and closed, how full the freezer is, and the level of humidity in the environment. Representatives from So-Low Environmental Equipment Co recommend defrosting when about half an inch of ice has built up on the walls of the chamber.

In this post, we’ll explain the steps you can take to make the process as painless as possible.

1. Make a Plan

Unless you’re the only one using your lab freezer, deciding on a whim to defrost it probably won't fly. Most likely other people are storing samples in there and will need to be notified.

All samples, reagents, or anything else being stored in the freezer with need to be moved to a temporary location. If you have another freezer holding the same temperature as the one you’re defrosting and it has room for samples, then this is ideal. However, if you don’t have this luxury, you may have to make do with a makeshift temporary storage solution. For example, a cooler or covered foam crate filled with ice could do the job.


Frost melting.


Finally, you’ll need to consider that all of the melting ice is going to become water, so you’ll have to be prepared to clean it up. Trays can catch runoff water, but you should keep rags and/or mops at hand too. Buckets or crates can be handy in case you get chunks or sheets of ice breaking away.

2. Empty and Unplug the Freezer

Once you’ve got your backup freezer sorted and all appropriate personnel have been notified, you can see to it that the freezer is completely emptied and the samples are moved.


Person removing samples from a freezer.


Then you can unplug the machine.

3. Speed Up the Melting Process

With the machine unplugged and the door open, the temperature of the freezer will decrease rapidly and the ice will start to melt. However, you probably want to get this over with as quickly as possible, so it makes sense to speed up the melting process.


A spray bottle spraying water.


To do this you can simply use a spray bottle or sponge and some hot water to melt the ice. Work from the top down and be ready to clean up the resulting water and ice with the aforementioned materials.

4. Dry Out the Freezer and Plug It Back In

Once all of the ice is melted and everything is cleaned up, it’s time to make sure the freezer is completely dry. If you miss this step, any residual water will form ice once the freezer gets back down to temperature. This won’t be a very good start after all the trouble you’ve gone to.

Once the freezer is completely dry, you can plug it back in and wait for it to come down to temperature.

And then you’re done! All that’s left is to replace your samples.