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Spray paint cracking


Pocster

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That's an adhesion issue. Is it going onto fresh, very smooth plaster?  I had very similar failure on the underside of a staircase, nearly drove me insane.

 

The only way around it was to get back to the plaster by scraping, and roller on LOTS of very very light watered down coats. I even went as far as roughly scouring the plaster with a bit of wire wool and brush. Any attempt to put anything remotely thicker just led to little flakes peeling clean off the smooth bits. I guess the same applies when spraying - lots of thin coats.

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8 minutes ago, SuperPav said:

That's an adhesion issue. Is it going onto fresh, very smooth plaster?  I had very similar failure on the underside of a staircase, nearly drove me insane.

 

The only way around it was to get back to the plaster by scraping, and roller on LOTS of very very light watered down coats. I even went as far as roughly scouring the plaster with a bit of wire wool and brush. Any attempt to put anything remotely thicker just led to little flakes peeling clean off the smooth bits. I guess the same applies when spraying - lots of thin coats.

I did mist coat everything with a basic white paint first .

Difficult to do “ thin coats “ with a sprayer !! . 

I’ll scrape back one window reveal ...

 

Once back to the plaster will mist coat that bit ( with a brush )

 

Worried about diluting the final coat paint as it might run - but guess that’s best .

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Once you've built up enough mist coats (maybe 4-5) - you should be able to put on a proper thick final coat without it peeling off.. It's a fine line though.

Brushing also seems to be the least likely to lead to peeling while applying - rollering is the worst as it essentially is pulling the paint off the surface. A sprayer might actually be good for that last thicker coat..

 

You could also just run a medium grade sander over it (e.g. 180grit) - this has the effect of flicking off any bits which are loose, while also roughing up the plaster and any good paint for slightly better adhesion for subsequent coats.

 

Either way, you have my sympathies here!

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I had this exact issue @pocster and for me the problem was too thick mist coat and probably next coat too.  Scraped off affected walls with glass scraper (slow job!) right back to plaster, easyfill where needed to repair then a new mist coat (wall still quite pink, 30-40% water).  Next coat was undiluted and covered almost all plaster colour followed by a final coat but again quite thin.  There is a definite knack to spraying!

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Scrapped back paint . Plaster underneath still has mist coat .

Tried baby sprayer . Blocked instantly. Had to dilute paint 5 to 1 to get it to spray .

Runs now of course !!

Will wait 10 mins between each spray and see if I can build it up 

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13 minutes ago, andy said:

I gave it 6-8 hours between coats, not sure building up will work?

I agree now !

Problem with baby sprayer as it’s so diluted it just runs .

I’ll leave it like this for now .

I need to get the girth Wagner out for the hallway once skimmed - so might go over this bit with the ‘ proper ‘ sprayer .

Just a pita cleaning the Wagner beast. !

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did you "tack rag" the surface before starting? -as any loose dust etc will stop adhesion

I just asked my plaster master mate 

his question was --"are you sure the plaster was FULLY dried out,"

as in weeks maybe 2 0r 3 weeks

-longer if in winter and hard plastered onto block walls which could have been be wet as well

   -definately not plastered on friday and painted on monday  

 hope it helps 

 

Edited by scottishjohn
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21 minutes ago, scottishjohn said:

did you "tack rag" the surface before starting? -as any loose dust etc will stop adhesion

I just asked my plaster master mate 

his question was --"are you sure the plaster was FULLY dried out,"

as in weeks maybe 2 0r 3 weeks

-longer if in winter and hard plastered onto block walls which could have been be wet as well

   -definately not plastered on friday and painted on monday  

 hope it helps 

 

Not sure what “ tag rag “ is - will Google .

Plaster about 2/3 weeks old so dry for sure .

Really only around Windows mostly - so with polythene on *assume* hotter than the rest of the house - drying too fast ???

Appreciate you asking a plasterer 

Edited by pocster
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Got my laser temp pointer thing . Windows definitely very warm . Also the front bedroom with minimum issues is lots cooler . Yesterday when spraying quite warm ( but not hot ) - today 23 degrees . 
But as I say walls / ceilings perfect . I’m sure it’s got something to do with heat  ( hottest day of the year so far !! ) . Hmmmmmmmm 

Edited by pocster
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On 29/05/2021 at 10:35, pocster said:

Aasrrgghhh !

Assume either went on to thick or simply dried out too fast .

What’s best ? Respray this ?

Dilute the paint ?

Gentle and carefully just use a brush ??

 

 

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why does it look black under the white --was it painted already?

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40 minutes ago, scottishjohn said:

using old out of date plaster?-which then never sets right  

without actually seeing it he could not be more specific

was another suggestion from my master plaster

Nah . I know it’s new because I got it .

I’m still going on the fact perhaps it just dried out too quick as it’s around the window returns . Polythene on windows . No airflow ( all locked up and don’t live on site ) . Hottest day of the year so far was the next day .

I might of course be completely wrong ?

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I had to emulsion about 50 picture frames (traditional St. Ives frames).  The first batch went well, then a new pot of paint, same make and type.  A few weeks later, they all cracked up, and oddly, double sided tape would not stick to them at all.

I now use a different make and type, and don't seem to have a problem.

 

Did you say you mixed paint up somewhere else and were it is cracking, is that the first part you painted?

Edited by SteamyTea
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this reminds me of a car I did a colour change on - what I did not know was it had had lots of repaints before  with a TPA paint 

the paint was so thick that when the new 2 pack  paint went on it softened the layers under it 

but the top dried  as it is a chemical reaction as well as solvent evaporation

 

and the under layers then shrank and gave a real orange peel effect 

 now if you have sprayed on lots of coats without allowing enough time for each to fully dry --then maybe this what ahs  happened 

under layers get sealed in with last cost which dried quick and then it softens as other coats attempt to vent out the water content  which would go into plaster and then come out ,but was sealed in

I,m guessing its water based  paint -- 

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Went into paint shop 

They claim that it looks like the plaster wasn’t fully dry .

It was left 2/3 weeks before I mist coated it . He then said perhaps the whole lot will crack and flake !! ? - thanks !!

Edited by pocster
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