Understanding Isopropyl Alcohol's Hygroscopic Nature

Today we are going to talk about a property of isopropyl alcohol that often goes undiscussed: its hygroscopic nature. Understanding this characteristic may incentivize you to change your storage and/or purchasing habits. 

What Does Hygroscopic Mean?

In simple terms, a substance is hygroscopic if it has the ability to attract and hold water molecules from its surrounding environment, primarily the air. This property means that hygroscopic substances can absorb moisture, leading to various implications and affecting its concentration and efficacy as a cleaning agent. 


  1. Dilution Over Time: As isopropyl alcohol absorbs moisture from the air, its concentration decreases. This means that the alcohol might not be as effective in cleaning the resin and other residues if it has been exposed to air for an extended period.

  2. Reduced Evaporation Rate: The more moisture isopropyl alcohol absorbs, the slower it evaporates. Alcohol has a high evaporation rate, so if you are tired of how fast your alcohol evaporates you may see this as potentially positive. However,  this can leave your tools wetter for longer (think atomizers), potentially affecting their performance or the taste of your concentrates.

  3. Change in Properties: As the solution dilutes, its surface tension, adhesion, and other properties change as well. As the surface tension increases the solution becomes more favorable to cavitation implosions within the solution. Thermally induced cavitation implosions may occur when dunking items that are above the liquids boiling temperature. We briefly cover the phenomenon in another blog post. 

  4. Purchasing Decisions: If you are not properly storing IPA, it might not be worth the extra money that 99.1% costs as it will begin to degrade the moment it is exposed to the air. If it comes down to buying the 99% or the 91%, you will be fine with the 91%, because the 99% will soon be 91% anyway. 

  5. Equilibrium Estimations: It's estimated that alcohol will continue to absorb moisture until it reaches an equilibrium of 65% alcohol 35% water. We can infer that in a high humidity environment this process could occur fairly quickly; over the course of several hours to a few days, especially if the container is left wide open and the air is moist. 

Best Practices for Using Isopropyl Alcohol

To mitigate the effects of its hygroscopic nature and maintain the efficacy of isopropyl alcohol as a cleaning agent, consider the following tips:

  • Store Properly: Keep your isopropyl alcohol in a tightly sealed container and store it in a cool, dry place. This minimizes its exposure to air and moisture, preserving its concentration and effectiveness.

  • Use Quickly After Opening: Once you've opened your isopropyl alcohol, try to use it within a reasonable timeframe. Over months, even in a sealed container, it can absorb moisture from the air each time it's opened.

  • Consider Different Usage Alternatives: Keeping ISO in an air tight spray bottle, or similar, may help preserve its concentration until its ready for use. 

  • Dry Your Tools Thoroughly: After cleaning with isopropyl alcohol, ensure that your tools are thoroughly dried before storing them or using them again. This can help prevent moisture-related issues, like water spots with glass or corrosion with metal.

Understanding the hygroscopic nature of isopropyl alcohol is helpful for anyone using it to clean resin residue from their tools. By understanding how it interacts with moisture, you can ensure your tools are cleaned effectively while prolonging their lifespan and performance. 

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