Choose the right IPA for build-plate cleaning before you blame a dirty PEI sheet for a setup problem
Loss of adhesion is often the first thing people notice when a build plate gets dirty, but the fix is not always “more alcohol.” Sometimes IPA is exactly the right tool. Sometimes dish soap and warm water work better. Sometimes the plate is clean and the real problem is still Z offset, first-layer tuning, or PETG gripping smooth PEI too aggressively. This guide is here to make that call simpler.
70 vs 91 vs 99
PETG on smooth plates
Soap and water still matters
Introduction: The Real Problem Is Usually Lost Adhesion, Not a “Bad Plate” Overnight
Most build plates do not go from perfect to useless overnight. What usually changes first is surface cleanliness. Finger oils, residue, leftover glue film, and material-specific contamination slowly erode adhesion until the first layer starts looking unreliable. That is the moment when many users start shopping for a new PEI sheet, a new surface, or a stronger adhesive. Often the smarter move is much smaller: clean the plate the right way and stop using the wrong cleaner for the wrong residue.
What Actually Matters: Cleaning vs Setup
Use IPA when the plate has fingerprints, light surface oils, or everyday contamination from handling and normal print use. This is where the “wipe it down and print again” workflow actually makes sense.
Do not expect IPA to fix bad Z offset, weak first-layer squish, poor temperature choices, or a plate-texture mismatch. A clean bed with bad setup is still a bad first layer.
If the issue only appears with PETG on a smooth PEI surface, the problem may not be “dirty bed” at all. It may be the material-surface pairing itself. In that case, use Best Build Plate for PETG Prints and our glue-stick guide for build plates before assuming stronger cleaning is the answer.
IPA Percentages Explained: 70% vs 91% vs 99%
| Strength | Best use | Why it helps | Main limitation |
|---|---|---|---|
| 70% | Fallback cleaning when stronger IPA is not available | Still usable for light wipe-downs, common in retail, and easier to find everywhere | More water, slower evaporation, and farther from the 90%+ lane Prusa explicitly recommends for print surfaces |
| 91% | Best default for most 3D printer build plates | Close to the 90%+ recommendation, widely available, and strong enough for routine PEI degreasing | Still not the right answer for every residue type or every material-specific surface issue |
| 99% | Best high-purity option for fast evaporation and minimal water content | Cleaner, drier wipe-down path when you want the purest common IPA lane | Does not magically fix sugar, glue, or setup problems that really want soap and water or a different workflow |
When IPA Works Best
Fresh oil and fingerprints
IPA is at its best when the surface has light oils from fingers, tools, or routine handling. This is the classic PEI wipe-down use case.
Routine PEI maintenance
For smooth, satin, and textured sheets that simply need a fast reset between prints, 91% or 99% IPA is the most practical everyday cleaner.
Quick no-rinse workflow
IPA works best when you want a fast dry-down without removing the sheet for a full sink wash every time.
That is why IPA stays in the core toolkit for PEI and steel-sheet maintenance. It is quick, predictable, and easy to repeat. But it is still a degreaser first, not a universal recovery tool.
When IPA Makes Things Worse
- When the user assumes a cleaner bed will fix a bad Z offset or weak first-layer setup.
- When the build plate has sticky residue, sugar-like buildup, or leftover glue film that responds better to soap and water.
- When the product is cosmetic or nail-care alcohol with moisturizers, oils, or other additives.
- When PETG on smooth PEI is already gripping too hard and the real answer is a separation layer or a different surface choice.
- When the bed is still too hot and the cleaning routine becomes sloppy, streaky, or less controlled than it should be.
Alternatives: Soap and Water Still Wins Sometimes
Dish soap and warm water are not old-fashioned fallback advice. They solve a different residue problem. Prusa explicitly notes that if adhesion keeps falling even when the user cleans with IPA, dish soap and warm water can remove oils and buildup that IPA does not remove well enough over time.
The plate feels clean after IPA but adhesion still keeps dropping, especially after longer use, repeated touching, or old glue-film contamination.
You want fast routine degreasing between prints and the problem really is fresh oils or light handling contamination.
For the broader build-plate decision itself, use Best PEI Sheets and Build Plates for 3D Printing. Cleaning and surface choice are connected, but they are not the same decision.
Common Cleaning Errors That Waste Time
Using 70% by default when 91% is easy to get
If the buyer can easily buy 91%, there is little reason to optimize around 70% for PEI cleaning. The stronger default is just a cleaner fit for the job.
Using skin or nail alcohol products
Cosmetic alcohol products may include oils or additives that are bad for print-surface cleaning.
Trying to scrub away a setup problem
A perfect cleaning routine will not fix a first layer that is mechanically wrong.
Ignoring soap and water
When IPA stops restoring adhesion, many users keep wiping harder instead of doing the one wash that actually removes the residue load.
Thinking 99% is automatically better in every case
99% is cleaner and drier, but it is not a magic answer for residue types that need soap and water instead.
Using IPA where PETG really needs a separator layer
If PETG is still welding itself to a smooth surface, clean PEI alone may not be the right target.
Best Products for Build-Plate Cleaning
91% Isopropyl Alcohol
This is the best default buy for most users. It tracks closest to the 90%+ recommendation lane, stays practical to source, and fits the daily PEI cleaning job without overcomplicating the purchase.
99% Isopropyl Alcohol
Use this if you already want the purer, faster-evaporating lane. It is a good cleaner, but the upgrade from 91% is about purity and preference, not magic performance.
Dawn Ultra Dish Soap
This is the smarter backup buy when IPA has stopped restoring adhesion and the plate clearly needs a deeper reset rather than another quick wipe.
Lint-Free Wipes
IPA works better when the wipe material is not leaving fuzz, lint, or softener-like contamination behind.
Refillable Fine Mist Spray Bottle
Useful when the buyer wants a cleaner, lighter IPA application instead of dumping too much liquid onto the sheet.