Blistering happens when the top layer of paint bubbles up due to loss of adhesion with the underlying surface.
It's mostly seen when using cheap paints but it can happen with any kind of paint, though it does seem to be more common in latex-based paints.
A number of factors that could cause paint blistering are listed below.
Older paints tend not to do this as much. Other factors include extreme temperatures during transit, storage humidity changes, poor application technique (i.e., using too thick a coat), chemical incompatibility between the paint and the surface being painted and finally, the interaction between several different types of chemicals used in the same area.
Paint bubbling happens most often when temperature swings within a short time span cause rapid humidity changes. If the paint container is removed from a cold area and placed in a warm damp area but not left there long enough to dry completely, this can make paint bubbles occur. You may notice some other symptoms along with blistering: the new paint appears milky, has an oily texture, and/or doesn't respond well to cleaning methods or stripping. When you try to clean it up, it smudges around and maybe leaves a dull spot here and there even after multiple applications of chemical stripper.
Blistering can also happen within 24 hours if latex-based paints are applied too thickly over oil-based paints (even epoxies), or simultaneously layered on top of each other. This results from the latex paint drying too quickly before the surface it's on has completely dried, causing a chemical reaction between two or more different paints. If you tried to do this intentionally as a technique, I guess it might be interesting, but the resulting effect would not be as pretty as oil-based paints can produce when mixed with water and blended in one layer.
Blistering may also indicate that there was something wrong with your paint mix if you were to make your own from scratch. Adding too much water to the powder, for example, or using powders that have been sitting around too long without being replaced would cause problems like this. So if you've ever experienced blistering in latex-based paints (especially over oil-based ones), then you have a good chance of being able to reproduce the effect on purpose. A professional might not have to deal with this issue if they were painting the interior of your house.What are the most common causes of paint blistering? Blistering happens when a top surface of paint film dries too quickly. If you've ever seen water drop on a piece of paper that's up against a window, then evaporate almost immediately once it hits the paper, what you're seeing is similar to blistered paint. The surface of the paint is actually drying faster than the underlying surface causing air bubbles to get trapped inside and push up from beneath until they get broken open at the surface, which causes the paint to bubble, creating blemishes or ripples in your coat of paint. If there are temperature changes, this can cause more rapid evaporation from the exterior paint towards the interior. It becomes slower and stagnant resulting in a reduced drying time on some parts while others are not dry completely. If you have paint with a lot of additives to keep it from drying rapidly, the outermost layer of paint dries in a way that creates air bubbles which in turn lead to blistering. You can identify this by looking for other symptoms in your paint, such as oily texture and dullness, after trying out some cleaning techniques on them without any success. Other causes of paint bubbling include improper surface preparation like painting on a dirty or hot surface/wall. Paint bubbles also occur when painting a surface with high humidity or excessive moisture. Also, improperly applying oil-based (alkyd paint) after applying water-based paints will cause bubbling paint, for instance, using a latex primer to prepare a surface to be painted with oil-based paint. There is no easy answer when it comes to why paint blisters because there are many different factors that contribute to it happening or not happening at all, even if you were to be using the same brand of paint.
Different paints have different ingredients, which can cause them to 'bubble' when they cure. The main ingredient in most primers and paints is resin, which comes from sap extracted from pine and fir trees or petroleum products such as crude oil and coal tar. The resin creates a chemical reaction with oxygen in the air when it dries after being mixed with solvents such as mineral spirits, hexane, xylene, or ethanol. This chemical reaction is called an oxidation reaction. When these two chemicals clash together during this process, heat is released, which may cause bubbles to form in your dried paint.
Many of the solvents used to thin and dilute paint are themselves organic compounds that can cause blistering in paints mixed with them when they evaporate from the surface at a faster rate than the rest of the painting sitting below, creating a chemical reaction that causes bubbles in paints. It's best to wait between coats of paint as well.The only way to guarantee that your paint will not bubble is to use water-soluble paints. These are usually used for surface decoration rather than protection. However, if the original purpose of your paint is to protect an object, stick with latex or oil paints - because they won't blister no matter what you do.
It's normal for latex-based paint to start paint bubbling after 24 hours. It takes longer for acrylics, oil paints and enamel paints. If it's drying too quickly, you can add Floetrol to slow down the evaporation process. This isn't perfect, though, since it slows down all coats of paint, even ones that don't dry as quickly, so it's best used on topcoats over lower coats that don't get direct sunlight after it's been painted on the object you're painting.The best way to remove bubbling paint is to sand it out with fine-grit sandpaper until smooth, then recoat patched areas with a fresh paint job. This may seem counterintuitive since you'd think that removing the blister would mean there's nothing pushing up from beneath, but in fact, you want to keep it even if it means scraping down into the old paint layer to make sure the new coats are flat over all of it.
If your blistering is minor and doesn't cover much surface area, you can try using a hairdryer or heat gun to heat the air trapped beneath instead of sanding off all your hard work. Just set the heat on the lowest setting and hold it about an inch over the surface of your paint. If you're using a hairdryer, hold it in one spot until the blister pops, then move to another area. When using a heat gun, move it constantly, or you'll burn your paint.
Some paint blisters may require a more elaborate paint job to fix. Ensure you wear the correct personal safety gear like dust masks and protective gloves for such paint jobs. Make sure nay paint you use doesn't contain any traces of lead. For more information, take a look at the this Australian Government guide to dealing with lead in paint.Check the paint's label for words like quick-drying.
Use Floetrol or another latex additive to keep the paint moist longer, but be careful because it will affect finish and adhesion if you add too much.
Slow down the drying process and time by covering your painting with a damp towel overnight while it's in an area that doesn't get direct sunlight. Only do this once before re-coating since doing it more often can cause puddling or unevenness in your paint coat(s).
Apply several thin coats of paint instead of one thick layer to slow down drying time even more. This is especially helpful when dealing with hot climates since heat speeds up evaporation.
Wait for at least three days before applying a topcoat. Don't sand the blister since that will just cause it to pop - scrape off the blistered part with a putty knife or razor blade instead. Clean your painting surface thoroughly before re-coating, especially if you used oil paint.
Be careful when applying primer and sanding surfaces before painting since this can also cause bubbles in latex paint coats.
When caulking has been applied, joints can cause paint blistering. Repair loose caulking, which may cause blisters or bubbles.
Choose the right nap length for your paint job for the right surface. A short nap roller cover is best for very smooth surfaces. A medium nap roller cover works best for surfaces with medium roughness. A long nap roller cover is suited for very rough surfaces.