Isopropyl alcohol is the default solvent in most cleanrooms, which makes it the default compatibility assumption. That assumption is usually right and occasionally expensive. IPA attacks some binders, swells some fibres, and leaves a residue signature that depends as much on the wipe as on the alcohol.
The first variable is concentration. The second is contact time. The third, which almost nobody records, is how the wipe was manufactured.
70% versus 99%
Seventy percent IPA is a disinfectant with a defined contact time; 99% is a solvent with fast evaporation and no meaningful disinfection claim. They behave differently on a wipe.
The water in 70% keeps the sheet wetter for longer and slows evaporation, which extends contact time with the fibre and any binder. The 99% grade flashes off quickly, leaving less liquid but a higher concentration gradient at the surface — which is why residue rings are often more visible after 99% wiping, not less.
| Material | 70% IPA | 99% IPA | Watch for |
|---|---|---|---|
| Polyester | Good | Good | Static generation when dry |
| Polypropylene | Good | Good | Softening at elevated temperature |
| Cellulose / pulp | Moderate | Poor | Loss of wet strength, fibre release |
| Polyurethane foam | Good | Fair | Swelling with prolonged soak |
| Rayon blends | Fair | Poor | Hazing, residue on glass |
The table is a starting point, not a certificate. Binders and surfactants used in finishing can change the answer for a specific product, which is why the supplier's compatibility data should name the actual reference, not the material family.
A wipe that sits in a puddle of 99% IPA for an hour is not the same product as one used for a thirty-second pass. Test the way you work, not the way the datasheet was written.
What happens to a pulp cloth in IPA
Cellulose absorbs water readily and alcohol less so. In 70% IPA the fibre takes up the water fraction, swells slightly and retains strength. In 99% the fibre dewaters, becomes brittle and loses tensile strength at the fold.
The visible result is a cloth that tears at the crease and leaves a halo on dark surfaces. The invisible result is a higher fibre count on the surface you just cleaned.
Residue is not always the wipe
IPA itself can leave a residue if it is technical grade rather than electronic grade. Plasticisers from a storage bottle, or salts from a diluted mix made with tap water, will show up as a haze and be blamed on the wipe.
Before changing the wiper, run a control: wipe a clean mirror with IPA from a fresh, sealed bottle using a known-good cloth, and let it dry. If the haze persists, the problem is upstream.
A compatibility test you can run
Cut four strips of the candidate wipe, each about 5 × 15 cm. Soak two in 70% IPA and two in 99% for five minutes. Remove, drain for thirty seconds, and test tensile strength by hanging a 200 g weight from one end while holding the other.
Record elongation, tearing at the fold, and any colour change. Then wipe a mirror with a fresh strip and inspect for haze under a lamp. Four strips, ten minutes, and a result that is specific to your solvent and your process.
The solvent list beyond IPA
Acetone and MEK are far more aggressive. They attack many binders, soften some foams and dissolve printing inks used on packaging. If your process uses ketones, specify a polyester or polypropylene wiper and verify the edge seal, because adhesives in sealed edges can fail in ketones even when the fabric survives.
Quaternary ammonium disinfectants are a different problem: they leave a film by design. The wipe has to lift the film, not spread it, which usually means a two-pass process with a water rinse or a second wipe.
Can I use the same wipe for IPA and acetone?
Often yes if it is polyester or polypropylene, but check the edge seal and any binder. Test both solvents separately; passing one does not imply passing the other.
Why does my wipe leave a white haze after IPA?
Usually extractables from the fibre or binder, sometimes residue from the alcohol itself. Run the mirror control to separate the two before changing products.
Is 99% IPA better for cleaning?
It evaporates faster and dissolves some soils better, but it is a poorer disinfectant and a harsher solvent for cellulose. Use it where the process calls for it, not as a default upgrade.
Compatibility is a property of the pair, not the wipe. Put the solvent name, concentration and contact time into the specification, and the choice becomes testable rather than assumed.
