Paid painters to repaint my room about a year ago, after a few months the white 'stains' started appearing.

I wasn't home and my parents were kind of overseeing the job, but they can't confirm if the painters actually primed the walls. They did tell me that the painters had to do a lot of coats, about 5-6 coats to get the colors on the wall. After scraping it a bit, the previous color is underneath the new paint so I think they painted over them.

It's all over my room and I can't seem to get rid of them through normal means.

Paint used is Dulux Pentalite

Does anyone know what is the cause and solution?

It's called efflorescence. It was caused by moisture in the wall.

I am not sure about the solution though. It happened to my new wall too because the painter paint too soon while the wall is still damp.

Wet wall problem. Is there aircon drain pipe or a water pipe in those walls? Or is that wall next to the toilet?

Usually need to scrape/sand down to bare cement and apply sealer/primer then only paint over with topcoat (colour paint) 2 coat.
5-6 coat seems dodgy like they tryna hide something.

I used bosch orbital sander with lots of rough sandpaper discs to sand down 30 year old paint coz old paint comes off the moment you roll on it (gunked up instantly the rollers).
The sanding looked like Iraq desert storm. Required 3M full cup N95 to breathe.

This post has been edited by ceo684: Jan 20 2021, 08:09 PM

I see. My room is connected to a toilet, I usually shower without closing the door

Not just the wall near the toilet has this, it's on every wall even the furthest from the toilet door.

So if I sand down, prime, and repaint using the same type of paint (Dulux Pentalite), I shouldn't be facing this problem again?

As you mentioned it happens on all walls.. does the whole house have adequate ventilation or its Tupperware style (windows never open)?
Suspect that there's more to this than meets the eye as the dampness may also be due to roof leaking (walls sponging up the water).

Are the walls esp affected area damp/cold when touched?
Plaster sound when knocked?

Need to chase down the root cause of the dampness before repainting otherwise same issue again.

This post has been edited by ceo684: Jan 20 2021, 08:54 PM

The entire house is quite well ventilated, except for my room as I usually close the door, and only open 1 or 2 windows.
The room at the other side of the toilet (sharing) doesn't have this problem, but that room wasn't repainted.

The other side of the affected walls in the other rooms is also fine.

This is my room. Windows on the right wall.


The walls feels pretty dry, including the white buildup, almost powdery like if I wipe with my fingers.
By plaster sound you mean hollow sound? Sounds solid when knocked.

For more context, the buildup somehow occurs mostly on the lower half of the walls. When it first started I did wipe with wet cloth, which will remove the buildup, but reappear after awhile.

https://www.bottompaintstore.com/blog/tag/paint-chalking/

I think what happened was you got frosting problem.

FROSTING:
A white, salt-like substance on the paint surface. Frosting can occur on any paint color, but it is less noticeable on white paint or lighter tints. On masonry, it can be mistaken for efflorescence (see Efflorescence and Mottling).

POSSIBLE CAUSES: Forms mostly in protected areas (such as under eaves and on porch ceilings) that do not receive the cleansing action of rain, dew and other moisture. Use of dark-colored paints that have been formulated with calcium carbonate extender.

Application of a dark-colored paint over a paint or primer containing calcium carbonate extender.

SOLUTION: Frosting can be a stubborn problem. It often cannot be washed off readily. Moreover, the condition can recur even as a bleed-through when a new top coat is applied. In extreme cases, it can interfere with adhesion. The best remedy is to remove the frosting by wire brushing masonry or sanding wood surfaces; rinse, then apply an alkyd-based primer before adding a coat of high quality exterior paint.

Removal by sanding down to bare cement plaster, wipe down whole wall using bucket and some soap solution with old t shirt/rags until not powdery, then use primer (nippon 5100/5400), then finish topcoat (colour paint x2 coat) will solve the issue. Looks like because old paint still there the problem never go away.

Basic sander without dust bag, uses sheet sandpaper (the rougher the better)
https://www.lazada.com.my/products/corated-...2-s2719085.html

Atas sander with dust bag:
https://www.lazada.com.my/products/bosch-ge...s170092766.html
https://www.lazada.com.my/products/dewalt-d...s100004558.html

both will create iraq desert storm level of dust, move out everything from the room before start sanding.
Hand sanding will be extreme level workout.
Would recommend at least the basic sander plus maybe 20-30 sheets of sandpaper. Even bosch brand sandpaper only RM1/ea at CSM 225 PJ

This post has been edited by ceo684: Jan 20 2021, 09:59 PM

This is paint formulation issue. Should contact paint manufacturer/painter to solve the problem for you. Wipe the wall first in one area and change water to wipe on another new area and see if the problem keep coming back.

This is normally caused by excessive extender/thickener used.

I guess it might really be frosting.

and wow thank you for the guide and advice, really helpful information!

MCO project otw!

Doesn't Nippon 5100 and 5400 have calcium carbonate also? If yes, won't this be a repeat of same problem? Alkyd primer would be like those oil based primer

Calcium carbonate is commonly used as extender in paint. It's just that formulation problem that incorrect formulations can often lead to this kind of problems and is basically the whole batch will be affected.

As it is due to old paint issue (and not water leakage damp wall issue) after removing the offending previous old paint to bare cement the sealer job is just to seal up the porous holes in the cement plaster so it won't suck up all the new paint (wasting expensive colour paint) as sealer is cheap in comparison.

Buying paints from fast moving stock places (paint shops or popular hardware stores like CSM) will get fresh stocks. Sometimes painters cut corner getting old base stock from unknown places will cause the said issue?

Certain batch of base might have the problem, can provide batch number to manufacturer directly to have them to rectify the problem. It could be the applicator but yea no harm to have them to rectify the problem for you.

Put a dehumidifier inside the room and see if that helps