Bubbles, blistering, pinholes: why bubbles appear on painted walls (roller & airless) — and how to avoid them

When we talk about “bubbles”, we often mix up three different defects:

  1. Bubbles/foaming: small bubbles visible during application (especially with a roller) which sometimes leave slight craters as they dry.

  2. Blistering: blisters formed after drying, due to a lack of adhesion (often moisture).

  3. Pinholes/craters: micro-holes or mini-craters left when bubbles burst or when the surface is contaminated (silicone/fat).

Understanding which one you have in front of you allows you to get straight to the causes… and the remedies.

1) Main causes, by type of fault

A. Bullage (foam) during application

  • Shaking too vigorously: shaking a half-full pot or mixing too quickly with a drill traps air.

  • Over-rolling / too fast a pace that “beats” the paint, unsuitable sleeve (too long a sheet on a smooth background), or too porous a surface that is not printed (the bubbles don’t have time to burst and become taut).

  • Heat/air flow: precipitous drying which freezes the bubbles before they disappear.

Note the formulation: all paints foam a little, so manufacturers include antifoams; but stirring, application and drying can stabilise micro-foam, especially in the waterborne phase.

B. Blistering (delayed blistering after drying)

  • Moisture on the substrate or exposure to moisture just after painting (wet rooms, condensation): the vapour pushes the film and loosens the coating.

  • Incompatibility or poor base: e.g. alkyd/oil on latex, dirty/glossy surface without preparation.

  • Overloading / too short inter-coat times or application in high heat: dry skin retains solvents/water which then try to escape.

C. Pinholes & cratering

  • Burst bubbles (linked to the causes of bubbling above).

  • Substrate contamination (silicones, oils, waxes, detergents) → “fish eye”.

  • Drying too quickly / film too thick / unsuitable thinner → “solvent popping” (or acrylic equivalent: trapped vapour).

D. Special features of airless spraying

  • Too high a pressure, unsuitable viscosity or the wrong nozzle can lead to micro-holes and poor atomisation.

  • Air in the circuit / sputtering (insufficient priming) = localised faults.

2) Prevention and correction: what needs to change in the application

A. Support & preparation

  • Cleans, degreases, removes dust and mattes glossy surfaces. Priming porous substrates (plaster/BA13, renders) before finishing.

  • Check for dampness: if you suspect a damp wall (after water damage, cold wall, poorly ventilated room), do the plastic film test (method inspired by ASTM D4263): tape a 45×45 cm polythene sheet, wait ≥ 16-24 h, look for condensation/darkening; presence = excessively damp surface.

  • Ambient conditions: comply with the manufacturer’s range. Example FT: 10-32°C, ideal RH 15-55% (max 85%) during application and the following 24 hours.

Wall dust removal - AI

B. Roller technique

  • Mix slowly (no shaking), allowing the foam to settle if necessary.

  • Choice of sleeve: on smooth walls/ceilings, keep it short (≈ 6-10 mm; 1/4″ to 3/8″ equivalent). Avoid foam with glossy acrylics.

  • Application: load evenly, pass at moderate speed, avoid ironing when the film “pulls”. Print porous backgrounds before gloss/satin lacquer.

  • If there are still micro-bubbles: allow to dry, remove fine dust and repaint, correcting the cadence/sleeve.

Roll again with the rolling pin

C. Airless settings & gestures

  • Priming: purge on restart until bubble-free jet. Spitting/air ingress results in pinhole-type defects.

  • Pressure: work at the lowest pressure to ensure complete atomisation; gradually increase pressure to achieve a full, elliptical pattern.

  • Nozzle & filtration: for standard acrylic interior walls, a 517 (or LP517) is a classic; 60 mesh filter for latex/primers, 100 mesh for more fluid products (lacquers, woodstains, varnishes).

  • Thickness: give preference to two thin coats (inter-coat time respected) rather than one thick coat (risk of bubbles/pitting). Coverage ≈ 50% and regular speed.

  • If pinholes appear: reduce pressure slightly, check viscosity (adapt according to FT), recheck filter/nozzle and evaporation time between passes.

Spraying with Wagner spray gun on door

D. Moisture management (blistering)

  • Do not paint on a damp surface and avoid immediate dampness after application (bathrooms: ventilate). Adhesion blisters often require scraping/sanding, appropriate priming, then repainting after removing the cause (leakage, condensation, etc.).

E. Contamination (craters/fish eyes)

  • Avoid silicone sprays, waxes and detergent residues. Degrease, rinse and wipe dry with clean cloths. In the event of a generalized attack: allow to harden, sand and repaint on a perfectly decontaminated surface.

3) Diagnostic express (check-list)

  • Immediate bubbles when rolled, leaving a “grainy” skin → slow down, shorter sleeve, slow mixing, impression if porous base.

  • Blisters raised by pressing several hours/days later → moisture/incompatibility; identify and eliminate the cause, rework the system (scrape/sponge/puncture).

  • Micro-holes/craters especially with spray gun → adjust airless/thickness, possible contamination; adjust pressure/viscosity, check nozzle/filter, degrease.

4) Good anti-bubble practices (checklist)

Before

  • Measure/evaluate humidity (plastic film test) and ventilate if necessary.

  • Choose a primer and finish compatible with the substrate.

  • Respect the T°/HR range of the FT and the inter-layer times.

For

  • Slow mixing; no shaking.

  • Roller: suitable sleeve, moderate speed, no over-rolling.

  • Airless: careful priming, effective minimum pressure, suitable nozzle/filter, 50% overlap.

After

  • If light bubbling: allow to dry, remove dust, repaint.

  • If blistering: remove cause of damp, scrape/sand, print, rework.

Not to be confused with: “greasy spots” ≠ bubbles

Sticky streaks/stains shortly after application of an acrylic → often leaching of surfactants, not bubbles; this can be cleaned up and prevent by better humidity/ventilation conditions.

Frequently asked questions (FAQ)

1) Why do bubbles appear when I paint with a roller?
Often: mixing too fast, over-rolling, sleeve too long or unprinted, highly absorbent substrate.

2) Do the bubbles disappear as they dry?
Some do, but if they dry too quickly they set and leave “craters”. It’s best to correct the technique.

3) How to avoid micro-holes with an airless spray gun?
Careful priming, effective minimum pressure, suitable nozzle/filter, thin layers, constant speed.

4) I get blisters the next day, what can I do?
Look for a source of moisture; remove loose areas, prime and repaint after drying.

5) Which nozzle should I use to paint a standard interior wall?
Often 10-12″ wide (e.g. 517) with 60 mesh filter for wall acrylics.

6) Can I paint in very hot weather?
Avoid: the skin dries too quickly, trapping air/water/solvents → bubbles and blisters.

Other blog posts to help you:

_________________________________________________

Love our content? You can find more here:

Visit our Facebook page

Check out our Airless Discounter YouTube channel

Airless Discounter Instagram account

Questions or queries?

For any further questions or if you would like to get your hands on one of these products seen in this article, you can contact us on +49 (0) 30 220 15436, fill out our contact form or email us. If you wish to purchase one of the products mentioned above, you can check them out in our online store. You can also visit us at our service base during office hours.