Lena Savoie
When it comes to disinfecting, a common misconception is that a higher percentage of alcohol is more effective at killing germs and viruses. However, this is not always the case. While 99% isopropyl alcohol is pure isopropanol, 70% isopropyl alcohol is diluted with 30% purified water, which allows it to permeate more fully, cross the cell membrane, and kill bacteria. This makes 70% isopropyl alcohol a better choice for disinfection and sanitization, especially in spas, where maintaining a clean and hygienic environment is crucial.
| Characteristics | Values |
|---|---|
| Effectiveness in killing bacteria | 70% alcohol is more effective at killing bacteria than 99% alcohol due to the presence of water in the solution, which helps it permeate more fully. |
| Disinfection | 70% alcohol is better for disinfection as it has a slower evaporation rate, allowing for longer contact with the surface being cleaned. |
| Sanitizing | 99% alcohol evaporates too quickly to be effective for sanitizing hands and surfaces. |
| Safety | 70% alcohol is less likely to cause adverse health reactions and has a lower chance of combustion compared to 99% alcohol. |
| Cost | 70% alcohol is cheaper for general use and large cleaning jobs. |
| Residue | 99% alcohol evaporates rapidly and is better for removing residue and water without leaving a film. |
| Moisture removal | 99% alcohol is more effective at drying out electronics. |
| Dilution | 99% alcohol can be diluted to lower concentrations, such as 70%, for custom formulations. |
| Electronics cleaning | 99% alcohol is better for cleaning electronics as it contains minimal moisture and can remove sticky residues and grease. |
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What You'll Learn
70% isopropyl alcohol is more effective at killing bacteria than 91% alcohol
It is a common misconception that a higher percentage of alcohol is more effective at killing bacteria. However, 70% isopropyl alcohol (IPA) is more effective at killing bacteria than 91% alcohol. This is because the water in the solution helps it to dissolve more slowly, allowing it to permeate more fully. The presence of water also slows down the evaporation rate, increasing the surface contact time and enhancing the effectiveness of the solution.
The disinfecting power of isopropyl alcohol drops at concentrations higher than 80-85%. A 90 or 91% alcohol solution is too powerful in some cases, as it dries before it can proliferate bacteria. This causes the alcohol to "'fry" the outside of the cell before it can penetrate the cell wall and kill the bacteria.
On the other hand, 70% alcohol is the perfect balance of alcohol and water, allowing it to cross the cell membrane and attack the entire cell, thereby killing the bacteria. This is true for most viruses and bacteria with an envelope structure, like the common cold virus and coronavirus.
However, it is important to note that there are exceptions to this rule. Some organisms with viral structures, such as norovirus, cannot be killed with any concentration of alcohol. In such cases, hand washing remains the most effective method for killing bacteria and viruses.
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99% alcohol evaporates too quickly to be effective
When it comes to using alcohol as a disinfectant, higher percentages do not always denote greater effectiveness. 99% alcohol evaporates too quickly to be effective. This is due to the fact that the solution does not have enough time to penetrate cell walls and kill bacteria. Hence, 99% alcohol is not suitable for sanitising hands and other surfaces.
The presence of water in 70% alcohol solutions slows down the evaporation rate, enhancing its germ-killing ability by prolonging surface contact. This allows the solution to cross the cell membrane and attack the entire cell, killing the bacteria in the process.
The rapid evaporation of 99% alcohol makes it ideal for cleaning sticky residues and grease. It is also suitable for use on water-sensitive devices such as integrated circuit adapters, computer chips, and circuit boards. However, 99% alcohol is highly flammable and requires proper ventilation and fire safety measures, especially in industrial settings.
The ideal concentration of alcohol depends on the specific application. While 99% alcohol is preferred for electronics cleaning due to its minimal moisture content, 70% alcohol is generally recommended for surface disinfection to allow for longer contact time.
In summary, while 99% alcohol has its advantages in certain situations, it evaporates too quickly to be effective for disinfection purposes. 70% alcohol, with its slower evaporation rate and ability to penetrate cell walls, is a more effective choice for sanitising and disinfecting hands and surfaces.
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70% alcohol is better for disinfecting
When it comes to disinfecting, 70% isopropyl alcohol (IPA) is considered superior to 99% isopropyl alcohol. This is because the lower concentration of alcohol in 70% IPA allows for a slower evaporation rate, giving it more time to permeate surfaces and kill bacteria. The presence of water in the solution helps it to dissolve more slowly, penetrate cells, and effectively disinfect.
The disinfecting power of rubbing alcohol drops at concentrations higher than 80-85%. A 90 or 91% alcohol solution may be too potent, causing the outside of a cell to dry out before the alcohol can penetrate and kill the bacteria within. On the other hand, 70% alcohol is the perfect balance, allowing the solution to cross the cell membrane and attack the entire cell, thereby killing the bacteria.
The slower evaporation rate of 70% IPA means it can be in contact with surfaces for longer, enhancing its germ-killing ability. This makes it ideal for general surface disinfection, such as doorknobs, handles, and workstations, as well as for removing microbes and bacteria, such as E. coli and salmonella, from surfaces.
Additionally, 70% IPA solutions have a lower chance of combustion compared to higher concentrations. Isopropyl alcohol forms unstable peroxides when exposed to air, light, and oxygen, increasing the likelihood of combustion. 70% IPA is also less likely to cause adverse health reactions and is cheaper for general use and large cleaning jobs.
However, it is important to note that the ideal concentration of IPA depends on the specific application. For example, electronics cleaning often requires minimal moisture, making 91% or 99% IPA more suitable. Additionally, in cases where water may cause damage, such as with certain electronic devices, 99% IPA is recommended to avoid potential water damage.
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99% alcohol is better for electronics cleaning
While 70% isopropyl alcohol is more effective at killing bacteria than 99% alcohol, the latter is better for electronics cleaning. This is because 99% alcohol has a faster evaporation rate and is a better solvent for water-insoluble contaminants.
Isopropyl alcohol is a clear chemical that is commonly used to clean electronics. It is effective, reasonably priced, and safe if handled properly. It dissolves a wide range of both polar and nonpolar soils and is often used to dissolve and remove light oils, fingerprints, cutting fluids, flux residues, carbon deposits, and mold release. It is also used to remove solder paste or adhesive from SMT stencils.
When cleaning electronics, technicians tend to prefer a fast dry time so that they can clean the electronics and bring them back into service as quickly as possible. 99% isopropyl alcohol is only 1% water and therefore will dry very quickly on its own, posing no corrosion risk.
However, it is important to note that 99% isopropyl alcohol can cause severe skin irritation and drying, so it is recommended to always use gloves when handling it. Additionally, it is not safe for rubberized surfaces or some plastics and can cause discoloration.
For most everyday purposes, it is recommended to not exceed 91% isopropyl alcohol, and 70% will usually be sufficient for cleaning electronics.
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70% alcohol is safer and cheaper
When it comes to sanitization and disinfection, 70% isopropyl alcohol is safer and cheaper than 99% isopropyl alcohol.
Firstly, 70% isopropyl alcohol is safer because it is less likely to cause adverse health reactions. This is because it is made up of 30% purified water, which slows down evaporation, allowing the solution to remain on surfaces for longer and enhancing its germ-killing ability. On the other hand, 99% isopropyl alcohol evaporates very rapidly, meaning it does not have enough time to penetrate cell walls and kill bacteria.
Secondly, 70% isopropyl alcohol is also safer because it is less likely to combust. Isopropyl alcohol forms unstable peroxides when it reacts with air, light, and oxygen, increasing the likelihood of combustion. Therefore, 70% isopropyl alcohol, which has a higher water content, is safer than 99% isopropyl alcohol.
In addition to being safer, 70% isopropyl alcohol is also cheaper for general use and large cleaning jobs. This is because it is more readily available and does not require further dilution with distilled or deionized water, which may be necessary for more concentrated solutions.
However, it is important to note that there are some instances where 99% isopropyl alcohol is a better choice. For example, in electronics cleaning, it is important to use a solution with minimal moisture to avoid damaging water-sensitive devices such as integrated circuit adapters, computer chips, and circuit boards. In these cases, 99% isopropyl alcohol is the preferred option as it evaporates quickly and leaves no residue.
Overall, while there may be specific applications where 99% isopropyl alcohol is more suitable, 70% isopropyl alcohol is generally safer and cheaper for most disinfection and sanitization purposes.
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Frequently asked questions
70% isopropyl alcohol is better for disinfection as it contains 30% purified water, which slows down evaporation, allowing the solution to remain on surfaces for longer and enhancing its germ-killing ability. 99% isopropyl alcohol evaporates too quickly to penetrate cell walls and kill bacteria.
99% isopropyl alcohol is highly flammable and vaporises rapidly. It can also cause adverse health reactions.
99% isopropyl alcohol is ideal for cleaning water-sensitive devices such as integrated circuit adapters, computer chips, and circuit boards. It is also useful for cleaning sticky residues and grease.
70% isopropyl alcohol can be used to create a cheap cold pack by mixing it with water and freezing the solution. It can also be used to disinfect hard-surface countertops when mixed with water in a 50/50 solution.
