Table of contents
Most people assume 99% isopropyl alcohol is simply the "stronger" and therefore better option. It isn't that simple. The only real difference between 70% and 99% IPA is how much water is in the bottle, and that one detail decides how fast it dries, how long it stays on a surface, and what you can safely use it on.
The quick answer
- Use 99% IPA when moisture is the problem: electronics, circuit boards, optics, precision parts, ink, adhesive and resin residue.
- Use 70% IPA when you need working time: routine wipe-downs of hard surfaces, tools, workbenches, salon stations and shared equipment.
- Not sure? If it plugs in or can't get wet, go 99%. If it's a surface you wipe regularly, go 70%.
What's actually different: 70% vs 99% Isopropyl Alcohol
| 70% Isopropyl Alcohol | 99% Isopropyl Alcohol | |
|---|---|---|
| What's in it | 70% IPA, 30% purified water | 99% IPA, under 1% water |
| Drying speed | Slower, more contact time | Very fast, flashes off in seconds |
| Moisture left behind | Some, needs a moment to dry | Minimal, near residue-free |
| Best for | Routine surface and tool cleaning | Electronics, lab and precision cleaning |
| Not ideal for | Powered or water-sensitive components | Large surfaces that dry before you finish wiping |
| Prep needed | Ready to use, no mixing | Use as is, or dilute if you need 70% |
Why The Water in 70% Matters
The 30% water isn't filler. It slows evaporation, so the solution stays on the surface longer and gives you more time to wipe away fingerprints, light oils and grime before it's gone.
That's why 70% is the go-to for everyday cleaning:
- More working time across larger areas like counters, desks and workbenches
- Easier to apply evenly with a cloth or spray
- Consistent results wipe after wipe
NCL's 70% Isopropyl Alcohol comes pre-mixed at 70/30, so there's nothing to measure. It's available in 32 oz and 1 gallon sizes.
Why 99% Wins For Precision Work
With almost no water, 99% IPA evaporates nearly instantly and leaves very little behind. That's exactly what you want when even a little moisture can cause problems.
Common uses where 99% is the better pick:
- Electronics and PCBs: removing flux, dust and old thermal paste from compatible boards and components
- Lab and cleanroom tools: fast-drying cleaning of compatible instruments and glassware
- Optics and precision parts: lenses and small components where streaks matter
- Residue removal: ink, adhesive and resin from non-porous surfaces
- Resin 3D printing: washing prints and wiping build plates
- Surface prep: degreasing before bonding, painting or assembly
NCL's Isopropyl Alcohol 99% is built for these jobs. For a deeper look, read our 99% Isopropyl Alcohol Uses guide. Comparing solvents for electronics? See Ethyl Alcohol vs Isopropyl Alcohol for cleaning electronics.
Common Mistakes to Avoid
- Using 70% on electronics that are switched on. Always power down and unplug. If you need to clean electronics, 99% is the safer choice.
- Assuming 99% is better for everything. On big surfaces it can evaporate before you've finished wiping.
- Skipping a spot test. IPA can affect some coatings, acrylics, painted finishes and screen coatings. Test a small hidden area first.
- Leaving the cap off. IPA evaporates and 99% also pulls moisture from the air, which lowers its purity. More on that in IPA Shelf Life: Does Isopropyl Alcohol Expire?
- Ignoring safety basics. Both are flammable. Use in a ventilated area, away from heat and open flames, and follow the label and SDS.
The bottom line
Pick by the job, not the percentage:
- 70% for routine cleaning where a little extra contact time helps
- 99% for electronics, lab and precision work where moisture is the enemy
Shop both, along with our full range of lab and industrial solvents, in the NCL Solvents collection. Need larger volumes for your business? Contact us for bulk pricing.
FAQs
Q. Is 70% isopropyl alcohol the same as rubbing alcohol?
Usually, yes. "Rubbing alcohol" most often refers to a 70% IPA solution, though some products use ethanol. Check the label for alcohol type and concentration.
Q. Is 70% isopropyl alcohol safe for electronics?
It's not ideal. The water content means it dries slower and can leave moisture behind. 99% is the better choice for electronics and circuit boards.
Q. Which is better for cleaning thermal paste, 70 or 99?
99%. It dissolves the paste cleanly and evaporates fast without leaving water on the CPU or heatsink.
