Why does paint blister and peel
Paint blistering and peeling?
You finally finished your painting project and are ready to enjoy a long-awaited result when you noticing that the paint has bubbled. And now you’re thinking “what’s gone wrong? and “what to do I do next?”
Whether you’ve done painting yourself or hired a painter and decorator for your project this is a quick guide to help you find a solution and understand the common causes of paint bubbling (“Blistering”) and delamination.
The cause is almost always faulty preparation
This cannot be stressed enough.
Surface preparation is probably the most labor-intensive, dusty and tiresome aspect of the painting process. In fact, the work area setup and subsequent preparation process accounts for up to 70% of painting costs.
Professional painters and decorators consider the end of preparation phase and the commencement of the paint application stage a milestone moment as the bulk of the hard work has been done.
Why does my newly applied paint bubble & blister, crack or peel?
Inadequate or faulty preparation is usually down to three factors.
- A lack of understanding or misconception about surface preparation and paint compatibility.
- Taking shortcuts and adopting an “it’ll be alright” attitude.
- Purposely ignoring preparation to save on time and costs
In regards to number 3. Some unscrupulous painting contractors purposely skip on preparation. As discussed before, the preparation is a large part of the painting costs. There are considerable cost savings to these characters. The lesson is “choose your painter carefully”!
Typical examples of paint delamination
Wet or damp surfaces: One of the most common causes of blistering paint is when fresh paint is applied over a wet or damp surface. This can occur on both new or existing surfaces.
Here are some things to consider in this scenario. Consider where the water is coming from.
- Is there a potential water leak?
- Could there be a leaking shower on the other side of the wall?
- If so, perhaps the silicon or tile grout shrunken or fallen away thereby causing water to get behind the tile and soak right into the wall? Perhaps the shower head or taps are leaking?
Even if the leak has been fixed already it can take weeks before the wall is completely dry enough to paint
On exterior surfaces, moisture can work its way behind the layer of paint through little cracks or gaps and can cause the coating to separate (de-laminate) from the surface (substrate). This is why correct preparation of surfaces is very important.
Also, it is wise to inspect your exterior walls for rising damp. Interior wall can be affected too. This too can often cause damage to paintwork. Applying a coat of waterproof sealer will help fixing this problem.
Also, on the interior, this defect can occur with new substrates as well. This is usually due to new plasterwork or Gyprock wall lining not having had an adequate opportunity to dry properly. There may have been a sheet of Gyprock nailed to a saturated timber. Always ensure that the surface you working with is dry.
No undercoat or sealer: Another common cause of blistering and delamination is the surface not having had an undercoat or perhaps having the wrong type of undercoat on the surface.
Whilst some types of paints are self-priming others require an appropriate undercoat. This can also depend on the type of surface you painting whether its new or existing and the condition of it. This is where knowledge in surface preparation is very important.
A good example is plaster-glass ceilings. They require an oil-based sealer. Without this type of sealer the paint will definitely slowly start separating from the surface. This then allows air and moisture to work its way under the incorrect paint thereby causing delamination.
Greasy or contaminated surfaces: The kitchen is potentially a high-risk area for this defect to occur. This is because kitchen walls and ceilings are often very greasy. If painted over without washing off grease and oil, it’s almost guaranteed to blister down the track.
The same phenomenon will also happen with surfaces that have been contaminated with some particular types of chemicals, usually harsh cleaning detergents or acids. Presence of silicon on the surface is another very common issue especially with new construction.
To avoid this, the best solution is to always inspect surfaces are clean, dry and free from any contaminants prior to painting.
Incorrect fillers: The choice of correct fillers for external substrates is very important. You might have wondered why there are so many different types of fillers on the market? The reason is that every surface requires the correct, fit-for purpose, filler
Some fillers are waterproof and flexible whilst others are not. Using a filler that is not waterproofed on exterior surface can easily lead to paint to blistering after the first rain. Also, filler that is not flexible enough can cause paint crack and blister over time as the surface contracts and expands due to temperature changes.
Excessively dusty or dirty surface: Having some dirty marks or scuffs on the walls or ceilings is generally not a problem however, having a lot of dust on the surface can lead to bad adhesion and further blistering. Ensuring that the surface is clean and free of dust will always prevent potential problems.
Very hot or cold surfaces: Extremely hot surface can also cause paint to bubble.
For example, painting an exterior wall on a very hot day. This will cause the coating to be touch-dry within minutes. The paint does not have the ideal time to dry (catalyze). This will almost certainly lead to delamination and/or blistering and any warranty the manufacturer offers will be null and void.
On the other hand, painting a very cold surface is a guaranteed risk of paint blistering. In this case the dying process is too slow.
You often find a temperature guide written on the back of a paint tin to assist you with understanding the correct conditions for painting.
How to fix Blistering
Step 1: Remove all loose or flaking paint until hard edges
Step 2: Inspect the surface and make sure it's dry and clean of dust grease and etc.
Step 3: Apply oil-based sealer and let it dry
Step 4: Fix patches with appropriate fillers. Sand smooth and dust off.
Step 5: Undercoat the whole surface and then top coat the whole surface.
Case Study
Last year I was called out to diagnose a problem by an exasperated gentleman who had been attempting to paint his daughter’s bedroom ceiling.
After carefully and methodically having ensured that he’d scraped the flaking paint back to hard edges he then started to paint by cutting in the cornices by brush and then, using a paint roller, he began to apply the paint to the flat surface area. To his astonishment the underlying paint began to come away from the ceiling and onto his roller distributing the debris on to the ceiling.
I immediately explained to the gentleman that the previously applied coating had been applied without proper preparation and, obvious from the peeling paint, had delaminated. Some areas had flaked and others had not. Nonetheless the previous coating was unstable.
Once the new paint had been applied, the moisture in the new paint had soaked through the previous paint layer weakening its adherence further which resulted in separation.
The issue was resolved by further scraping and the application of an oil-based sealer/binder whose fluids seeped into the old paint coating to adhere it solidly. The product name is sealer/binder. It “binds” and “seals” old paint back to the substrate thereby allowing you to apply your finish coats properly.
Please feel free to contact us for assistance with your painting maintenance on 0407 505 044 or This email address is being protected from spambots. You need JavaScript enabled to view it.