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"crazing" Just like an old china plate

4K views 16 replies 9 participants last post by  Greg from K/W 
#1 ·
I don't know what caused this. Its an original plaster wall with a network of very fine cracks. The wall feels sound. It really does look like those fine cracks in old china. Would a superior adhesion primer 'glue' it all together? ( They are very faint, almost not noticeable.) I considered priming with Weld-bond first, then primer. Otherwise it would seem a job for a plasterer first. Its only 1 wall 10 X 6. The opposite side of the wall is not effected. There is an exterior door near by.
 
#2 ·
Weldbond might work, but it would be non sandable, and create it's own set of problems I think.
Could it be possible that some one painted over old wallpaper glue.
I have seen that "craze" before.
I might try sanding the heck out of it, and then priming. See how it looks.
There used to be a wallpaper type product that could be applied before painting.
Sorry I can't be of more help.
Good luck:thumbsup:
 
#5 ·
No, You have been a terrific help! That sounds like you nailed it because in most areas they just painted over the wall paper. For the most part stripping has been easy. A wide blade and huge stiff sheets just peel off easier than an orange. I am willing to bet my butt what I am looking at was caused by old paste. The paint is modern latex so it wont be lead. I will power sand and prime well, it should be fine. Aqua-lock will cure it. :thumbsup:
 
#4 ·
This can be a very common problem with old plaster walls.The keys may be broken in places allowing the plaster to move when the door is closed. If the plaster in general seems to be attached to the lathe and not pulling away from the wall you might try a 2 coats of peel bond,that should hold it together and then top coat with your paint of choice.If the plaster is pulling away from the lathe you will need to re-attach with plaster washers... that's another topic for another day.
 
#7 ·
The wall seems sound as rock. If it was the door, both walls would be effected. And really, they are not "cracks" just a surface thing. I going on the wall paper paste theory. It looks to make the most sense in the situation.

BUT​

What are "The Keys"? Forgive my ignorance, I had not heard the term before you mentioned it.
 
#6 ·
P.S. No, Weld-bond does not sand well but thinned it will is a great base to prime over and the primer sands well. So my method in doing that kind of thing is to coat once with a light coat of weld bond, wait 24 and prime, sand well and prime again. Its a cure I have used in other doubtful situations and has worked well for me in the past. This is a larger area than I'd ever done that to prior. I had no doubt it would work but it is twice the work. I'm glad it will not be required.
 
#8 ·
"keys" = the plaster that squeezes between the lathe ...that is what holds the plaster in place. When the plaster that squeezes through the gap in the lathe (keys) breaks the plaster becomes loose.This is usually found to be a problem in pre 1900 homes,the base coat was mixed with horse hair to make it stronger, they thought,after 1900 the mixed was changed,horse hair was removed and hardeners made the mix stronger.
 
#9 ·
Thank you. So when I remove the rubble and create a Durabond base in the lathe work, I am in effect, creating "keys", right. I am just a painter so my patches tend to be Durabond 90 and a top coat of drywall mud. It seems to hold up well because I have never had a complaint. The house with the problem is 1912. The keys look a lot like the mortar used with brick.
 
#12 ·
Maybe I'm not reading this right but to me it sounds more like the paint is like an alligator skin than the plaster being loose. If the keys were broken would you not feel some movement in the wall, and he said the wall was solid. If thats the problem could you not just lightly sand then skim coat the wall with that new ultra lite joint compound in the bucket with the puke colored lid-I just used it to skim coat some walls and for that it's great-sand prime and paint.
 
#14 ·
No, I have plenty of experience with finishes doing the alligator thing. (Cold, mis matched paints, etc.) This is a cracking effect that seems well adhered to the plaster, it just has this faint VISUAL crazing effect. I can not feel it at all if I run my bare palms over the wall. I have not attacked that wall yet, I'm still burning paint off wood. When I get there I will use the method that has worked for 30 years. Aqualock X 2 coats and -power sand. That will give me a perfect wall, I think. Final coat of prime and paint.
 
#13 ·
sounds to me like wallpaper glue painted over, pretty much like the crackling product is, glue. Some people think that you can just paint over glue instead of washing it off.Often they use an oil base but even that isn't effective. You could always use a carbide scraper and see if the paint or the plaster is the culprit or test to see if the top skim coat of plaster is detatched ,if it is just floating on top, a sharp chisel will tell the tale, if it is just one small wall you gotta wonder.
 
#16 ·
Crazing happens to all plaster, it is normal and considered acceptable to a degree. I had many thousands of square feet that we did many years ago and it was exterior. It only showed up when wet btw. It freaked us out when we discovered it by accident. (Dry, it was invisible.) The owner of the company pulled out the code book and national specs and showed the head honcho that small amountsare considered acceptable.

Ok here is what I would do: My base coat would have some elasticity in order to bridge the crazing and to not have it reflect through your final coat..whater finish that is.

I am not sure about what products that you state you use. Just make sure they have a good elongation factor and you will be fine.

Hope this helps.
 
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