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Porous Areas on Drywalls Causing Issues on Painting

Porous Areas on Drywalls Causing Issues on Painting

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  #1  
Old 05-14-13, 08:00 PM
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Porous Areas on Drywalls Causing Issues on Painting

Hi, Everyone,
I would like to get your thoughts on how to fix the "flashing patches" on the drywalls caused by porosity. These patches absorb paint (and primer) and make the uneven appearance on drywalls.

The story is that I just started the project of painting the interior walls of my house. The interior walls were with "builder's flat white," and I decided to add colors to them. In the first room, I primed the wall with Valspar Latex Primer-Sealer, and then painted the wall with Valspar Ultra Primer+Paint as the topcoat. There are still patches of "shadows" showing up after these 2 coats. By looking closely, one can see small white dots and pores in these patches. This tells me that the 1st coat of primer-sealer is not doing a good job. Another coat of primer+paint on these patches did not seem to work well, since the patches show up again.

What is your recommendation on doing "spot-repair" on these patches? Would you recommend using a high-build primer and then paint with another coat of primer+paint?

Since I just started, there are still a lot of drywalls to paint. What would you recommend to use for priming the wall before the primer+paint?
Thank you!
 
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  #2  
Old 05-15-13, 04:30 AM
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Welcome to the forums!

I'm not real familiar with Valspar's modern day coating line up but I suspect their primer wasn't up to the job. I suspect your walls were originally painted without a primer Zinnser has several primers that do a decent job of penetrating builder's paint and locking it better to the drywall. Most any paint store [not a paint dept] should have primers that will also work well. I wouldn't use a hi build primer.

By looking closely, one can see small white dots and pores in these patches.
This almost sounds more like an application issue than a primer/paint issue. How did you apply the paint? what size roller cover? how far did the paint go? What type of texture is on the wall? A liberal coat of paint applied with a 1/2" nap roller might fix the issue.
 
  #3  
Old 05-16-13, 07:52 PM
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Mark, thank you for your recommendation!
(I did write a reply last night, but somehow it was not attached to this thread! Let me try it again....)

To address your questions - I used a roller of synthetic fiber (that is, not the sponge type) with 3/8" nap to paint the wall. As for "how far the paint went," are you referring to whether the paint seemed to run out quickly from the roller? Sometimes it did seem to be so. Sometimes I had to load the roller frequently. (Since I am new to painting, I am still learning how to load proper amount of paint to the roller. Any recommendation on how to figure out when there is too much or too little paint on the roller?) In terms of the texture on the wall, they are not as smooth as wood. There are still plenty of small lumps and "valleys" if one looks very closely. Not sure whether they can be called "typical" drywall. Your question on the wall texture makes sense. Possibly the 3/8" nap is not thick enough to work with these drywalls.

I went to the hardware store today and got one gallon of Zinnser Bulls Eye all-purpose primer/sealer, as well as roller covers of 1/2" nap. I will test on the weekend with the following plan:
Plan A - Adding a topcoat of paint on the porous areas with the roller of 1/2" nap.
Plan B - In the case Plan A does not work well, apply Zinnser primer/sealer on porous areas before another coat of paint.
(Any suggestion on other approaches?)

Another question I have is your thoughts on the necessity of using primer before the topcoat, especially when using paint containing primer. I have read discussions on both the yes and no sides. What do you think?
Thank you again!
 
  #4  
Old 05-17-13, 04:46 AM
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I don't have much confidence in the priming ability of the primer in the paint coatings. I believe it's more of a marketing ploy than anything else. There are many different types of primers made for various jobs. When a primer is needed it is best to use one that is tailor made for the job at hand. Most repaints don't require a primer.

It sounds like your walls have an orange peel texture. 1/2" nap almost always works best for slick finish or lightly textured walls. 3/8" nap is for ultra slick surfaces and even then a 1/2" is often preferred because it holds more paint - will cover more ground and is quicker. I like to 'slop' the paint on the wall and then as the roller becomes drier, even it out neatly. A roller well lubricated with paint will cover better and be easier to use than trying to stretch out all the paint in the roller. Forget about any N or W pattern you may have read about. Usually it's best to make 1 stripe up and down and then go over the previous stripe before reloading the roller. I prefer to roll out of a 5 gallon bucket but when I do need to use a tray, I only use the deep pans, not the dime store trays that are shallow.
 
  #5  
Old 05-23-13, 07:07 PM
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Mark, sorry for late reply!
I would like to report the result of using the roller cover with 1/2" nap. The fact that it can hold more paint has made it much easier and smoother for painting. More abundant paint can be rolled on the wall with this new roller cover. The terms you used - "orange peel" texture - to describe the walls are very accurate! Using the roller with the thicker nap helps a lot on covering off the patches with white dots, even though these patches cannot be fully "elimiated." Very often I had to make an additional "roll" to ensure that they were covered with sufficient paint.

I also paid attention to how I used the roller, since you mentioned "application issue" in a previous message. I noticed that I still kept on rolling on the wall even though the roller was running low on paint. This could be where the issue of "porous patches" stemmed from -- I have been "stingy" with paint, felt reluctant to pour too much paint into the 5-gallon bucket, and tried to "squeeze out" as much paint on the roller as possible to the wall. This could be the reason for the uneven coverage of the paint on the wall. Going forward, I will need to get the habit of reloading the roller before it is fully "drained."

Your instruction on how to use the roller on the wall (using the up-down motion, not the N or W shape) is very helpful too. I still need to practice on manuvering the roller, and on spreading out the paint evenly after saturating the roller with paint and making the very first up-down stroke.

Overall, it has been working much more efficiently than before. Thank you very much for your advice and instructions!!
 
  #6  
Old 05-24-13, 03:31 AM
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Glad you got it figured out
With a little practice you'll find it easy .... not sure I'd have painted for 40+ yrs if it had been hard to do
 
  #7  
Old 05-28-13, 10:17 AM
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It may be easy for you, but it is not so easy for me. I bet you can do it in your sleep. I am far from there yet! Still practicing....
Have a good one!
 
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