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What caused the finish coat to separate from the brown coat plaster ?
I have worked on many plaster walls & ceilings that were any where from 200 years to 150 years old & the finish coat was not separating, but I have seen a lot of drywall mud over plaster fail. My thinking on the OP project is that the new applied Joint Compound over the plaster substrate will have cracks at the edges or the existing skim coat edge material will separate I give it 60 days after it is completed.

If that was even remotely true, the plastering industry would still be a vibrant industry.

However its not. Its dead. Instead, PAINTERS are patching PLASTER with drywall compound, and CALLING it plaster...

And 99% of the time, it holds..... FOR DECADES...

Just saying.
 

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the plastering industry would still be a vibrant industry.
However its not. Its dead.

I disagree, while the majority of houses use regular drywall there are quite a few hi end houses that use blue board and a plaster veneer. Plaster is still superior but it costs a good bit more so it's not as prevalent as it once was.


That said I've never had any call backs from repairing old plaster with drywall products although with repairs I normally use Durabond and not ready mixed joint compound.
 

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If that was even remotely true, the plastering industry would still be a vibrant industry.

However its not. Its dead. Instead, PAINTERS are patching PLASTER with drywall compound, and CALLING it plaster...

And 99% of the time, it holds..... FOR DECADES...

Just saying.
The reason for the decline in the Plaster trade was due to the invention of Drywall. The drywall was cheaper in cost less labor to install / apply is the reason for it's decline. As for the Plaster trade being dead that is some what correct due to the skill required to apply Plaster & make it smooth.
As for it working for 99% of the time that depends on a lot of facts that have not been covered as to why the failure occurs.
Yes Joint Compound over Plaster will last for DECADES but when it fails is where the cost is that out of reach of many home owners. I was in the Plaster Trade for 14 years & during that time period I have repaired hundreds of structures that had Joint Compound applied over the Plaster some lasted 5 years & others lasted over 20 years but all failed at some point. This is where I made my big - big profits. It got to the point that the State I am in would call for me to repair Very old buildings that the only problem was Joint Compound applied over Plaster. A small example of cost to repair a ceiling 22 feet X 20 feet =440 Sq./Ft. @ a cost of $10,000.00 repair time was limited to three days total man hours total labor & material cost was $4,500.00 can you do that in 3 days with drywall? The last job I did before retirement was a very high profile Gov't Historical structural in Charleston, SC at the pre bid meeting I made a statement that the specs. were incorrect for the repairs required I was informed that the specs were correct & the pricing was to be as per specs. I elected to follow the advice of that meeting. My price was very low compared to the other received I did git the job to do the repairs $250,000.00 your taxes @ work. When the job got started & was well under way I pointed out the problem of the delamination & cracking of the Plaster finish to the resident officer in charge construction ( ROIC ). I was than asked when I was aware of the problem when I told the ROIC work was stopped.
What happened next after some long delays was I only had to complete the areas of repairs that were started & was told not to complete the total project
This is your tax dollars @ work can you make a guess @ the profit that was paid due to a contract had been signed & the specs were WRONG due to the spec writer not being aware about the long lasting effects of Joint Compound over Plaster. To this date the Plaster crews are still repairing plaster with drywall mud applied over it. For 20 years I made 10 time times the amount of money that it cost to apply Joint Compound over Plaster keep it up it is very good for the plaster trade & I love it.
 

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Discussion Starter #27 (Edited)
Ok, I applied the 3rd coat today.
I used all the tips you guys told me.

1) I wiped down the ceiling first. I totally think this was the issue last time. The boogers were dried nugs from the prior coat. This really prevented booger tracks.

2) I thinned mud with a dab of water (spoonful)

3) I loaded about 3 spoonfuls of mud into the pan. Way less. The mud was in the pan a lot less time now.

4) As soon as I got booger tracks, I dumped the mud out, and reloaded. I think before starting I should have wiped down the entire ceiling, not just wipe as I went along the room. That way, one less thing to remember

This all led to a much easier time. Swipe the 12" and was left with a perfect smooth finish. Tight scrape, and I will not be sanding this last coat, which was my goal. Yes, one can for sure fix holes with JC and not sand anything.

Thanks for helping me through this project.
You guys rock.
@Yodaman
@mark sr
@mathmonger

Next step is to primer and then paint.
I will be back in Aug.
 

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Discussion Starter #28
I went over a few missed rough spots for a 4th coat.
I used the small knife and it was quick and no mess.

Today, I applied primer over the entire ceiling.
A few hours later, I applied flat white paint.

I can still see imperfections, but it looks 100x better than before!!

Now, it's time to paint the walls.
I don't need to primer if I'm just doing a color change, right ?
Walls are in good shape.
 

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Discussion Starter #29
The room came out amazing.

I finished the ceiling.
Did a coat of primer.
Painted it with ceiling paint.

Painted the walls yellow.
No primer except on a few repairs spots.

Pulled the rug to expose hardwood floors.

Tossed the boxspring bed and got a storage bed from Ikea.

Got all new furniture. Dressers, desk, lamps,etc.
New blinds.

Whole room looks great, and the ceiling was the first step.
Thanks for all the help!
 
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