I’m coming down the home stretch with a big patch. Since there are some challenging angles (eave) and a soft inside radius, I chose to use lath and plaster instead of drywall. I like plaster anyway and although I’m far from being a pro, I’ve had some experience with it. I’m using some Plaster Weld in the joint but to make sure the plaster/drywall connection doesn’t crack, I’d like to tape it with setting compound and then skim the whole thing out a little with topping. There will be old paint on the drywall side, new lime putty finish on the plaster side.
Plan 1: TSP the old paint… tape the joint with setting compound… skim… then prime and paint.
Plan 2: prime both old paint and new lime putty finish… tape the joint with setting compound… skim… re-prime… paint.
Which plan will give me the best adhesion for the setting compound? Thanks in advance!
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Jeff
either way.
tsp will provide an excellent bonding surface. i'd also use fiberglass tape to prevent cracks.
Expert since 10 am.
So, how'd you finally decide to handle it?
Peace out.
I just got done with the finish plaster today! Thanks for asking! I've decided to let the lime putty finish cure for a month (it's my understanding that's necessary before you can apply paint. Correct? Something about the extreme alkalinity of lime putty.) Then I will prime the whole room. I will then tape the seams with setting compound and follow up with a couple of passes with joint compound. Finally, if I think it will improve things, I will skim with topping. Re-prime and paint. A little bit of a shlep, but I think it will look good by the time it's done.
Over a month for the room? You must not be married.
Passing along a bit of advise that I got from an old plasterer (found him based on the recommendation of someone that still sells REAL plasterboard. The stuff w/a brownish paper on it.). He said to let the plaster cure (I thought he said 6 months but it could have been shorter) & before priming & painting, wash it with a mix of vinegar (distilled) & water. He didn't say how much vinegar but my impression was about 25%. I guess it neutralizes the basic nature of lime.What I ended up doing (this was a "patch" of an old doorway) was letting it cure for several (cough cough) years and then washed the whole bedroom with the vinegar/scalding hot water mix. Let it dry & used Zinser primer/sealer & painted it a beautiful under-Caribbean-water bluish/green.Name change list: Gizmo, Gremlin, Kitsune, Kiya, Shelby, Slinky, Snot & Velcro.
If you use white vinegar as your retarder, it will help speed up the curing. Let the plaster totally dry and then giv it a wash with vinegar and water. Dry again and paint.
When you say "white vinegar" what do you mean? Obviously it's not (heaven forbid!) balsamic or apple cider. Is white vinegar the same as distilled?I found out the other day that a mix of distilled vinegar & scalding hot water helped IMMENSELY in taking off a wallpaper border(not vinyl). This was without ANY damage to the plaster underneath. Some paint did come off but since I'm priming & painting anyway, it's not a big deal.Name change list: Gizmo, Gremlin, Kitsune, Kiya, Shelby, Slinky, Snot & Velcro.
"Is white vinegar the same as distilled?"Yes
Jer, I'm learning as I'm going here... Since the finish plaster is already up, it's too late to add vinegar to the mix... But when the plaster is dry in a few days, if I wash with vinegar can I vastly shorten the month long period of time I was going to allow for curing? Or does it need that time even if it's going to be washed with vinegar? Thanks.
Did you do this job as the traditional three coat plaster process? If so, then you have to wait for the plaster to completely dry which is the thing that takes a long time. If it was just a skim of white on plasterboard, treated sheetrock, blue board, whatever, then it shouldn't take that long for the plaster to totally dry & cure.
The reason for the vinegar is to neutralize the alkalinity of the lime so any moisture that may be in the brown and scratch coats won't cause the salts to come through causing efflorescence under the paint, and therefor breaking the paint bond and separating it from the wall.I love to plaster the white coat in the traditional lime putty, it's how I was trained. Nothing gives you that ease and plasticity of a material like the traditional lime and gauge mix.
But lime has its drawbacks. First, you really have to protect yourself while working with it. There are some real horror stories of the old "quick lime" that used to come in large blocks and you had to slake it to the putty stage just like you do the bagged finish lime of today. It was much more caustic in the dried out blocks and if you got any of that in your eye, you were really screwed. The vats of water used to almost boil when the quick lime was dropped into it. Same way with bagged finish lime except it's not as bad because some of the water has been retained and that's why it's call 'partially hydrated' lime.
Secondly, you have to slake the stuff which is messy and takes time.I don't really plaster anymore except to do skimcoating and plaster repairs. When I do the repairs, it's always the finish on top of a piece of sheetrock unless the customer wants the traditional three coat.
The white coat that I use anymore is a mix of regular lite joint compound (blue top), and gauging plaster or plaster of paris, mostly the latter because it's more readily available. The mixing is done the same way as with lime.Bottom line is that plaster should be totally cured & dry before the primer & paint.
Yes, this is a three coat traditional plaster. The scratch and brown are a sanded base. I used Redtop Plaster, mixed it 1 plaster to 2 1/2 sand... A few days later, I mixed type S lime with water to the consistency of sour cream, let that sit overnight and then folded in slow set gauging plaster on a mixing board. It's the old way of doing things but even though it's time consuming, it's a very satisfying thing to accomplish. Recently, I used this method to plaster my own bathroom (another project, yet to be painted). Thanks to the internet, I was very fortunate to have a pro usher me through. I even learned about dots and screeds. Loved it! Yes, lime is scary stuff. But it's my understanding that the autoclaved lime (type S) has all the fury taken out of it. It mixes up peacefully. Apparently, it's good to let it age, but not essential. But it's still extremely caustic (eye protection!) and the alkalinity problem remains. Thanks for the explanation of efflorescence, which makes perfect sense. Is a month enough time to let all the water escape? With regard to paint, I was going to call the tech people at Dunn Edwards and ask... I have also heard that oil is preferred but I thought I'd ask to be sure.
The plasterer I used told me to let it cure for 10 days. We generally went about 14. Now I don't know if what you used is the same as what they used, but my advice is the same either way: check with the manufacturer! They should know.And I vote for plan 2: prime everything first. And I have also heard that an oil based primer is better.
That's great that you're working it the traditional way. Yes, it is very satisfying to get a handle on a trade like that which has dwindled way down to a very few, and practice it.
A month is about the time that we used to let it go before painting. If it's in a heated home, then there should be no problem.If you want to do some reading on plastering, the plasterer's bible (in America) is 'Plastering Skills' from American Technical Publishers Inc. It's the handbook that you're given when you join the plasterer's union.In Italy, there are great vats of lime which are set in the ground that soak for years before they are used. This lime is very pure and fine and it is the stuff which is used in the artistic gessos and fine Venetian plasters, encausticas, Marmorino etc. They mix it with fine marble dust as a type of aggregate. If you learn how to utilize the dot & screed method, all you need is a plumb bob and a piece of string to get a perfectly straight wall.Plastering is cool but to do it day in and day out for a living is hell on the body.
Jer, Yes, I have Plastering Skills and used it extensively when I did dots and screeds. And, yes, I used the plumb bob with a partner... with the string sliding along the 'L' shaped piece of wood at the bottom dot while I mushed in the top dot. The walls came out very plumb and very flat. They did not come out perfectly square to one another but they aren't off by much. That's a mystery I still have to unravel someday. I also used the dot and screed method to get a very level ceiling, which I plastered as well. You're absolutely right about it being brutal. I did this virtually alone and it nearly put me under. But all that aside, I learned enough to know that it's a marvelous material and that a real pro has quite a formidable set of skills.
We would make a large square triangle out of clear cedar or some other straight stable wood and use it when we were browning in the corners. Dot & screed one wall, then square one corner of it and work your way around the room. Sometime I would just use a regular 24" dedicated framing square to screed up a nice square corner when I was brown coating. That works well too.A little tip...you want the base plaster to set up in a couple of hours? throw in some dry lime to your mix. I like using perlite plaster (Structolite) because it's nice and light, add a little dry lime to that and it will be hard by lunch time.
The sanded Red Dot is good strong stuff, but do nothing but ceilings with it high up and you really feel your age at the end of a day. The shoulder and the neck are shot! Then do it for weeks on end...
Jer,The root of my out of squareness problems arise from not having someone there who really knew what he was doing. I had a complicated situation... out of square and out of plumb framing. And a floated tile wainscoat that wasn't yet installed. So I set up temporary plaster grounds at the floor using control lines that I had snapped for square. But because of the framing out of plumbness I had to try to finesse excessive plaster thickness problems... and you can see the process became rather tortured. Somehow I managed flat and plumb plaster but not quite square... and I was probably lucky to get that far. I had to smile at your suggestion of how to speed up the set of the brown coat. That might have helped on the days I set up the screeds. But it was never in my mindset to ever consider speeding up the set. I had a morbid fear the plaster would outrun me. The plaster never got ahead of me on the wall, but it did once in the wheelbarrow (made the mistake of having lunch) and that made for a trying day. I chose a sanded base over Stuctolite because I think it ends up a stronger wall, and there was one other thing. The plasterer who mentored me said that if I intended to use a lime putty finish, I would have to add some sand to the putty to weaken it a bit if I used Structolite as a base. Apparently, there can be expansion differentials between Structolite and straight putty and I risked cracking. The added sand adjusts for that. He said that why products like Whitekote, veneer finish plasters right out of the bag have some fine sand in them. But to keep things simple, albeit heavy, I just went with a sanded base and a lime putty with nothing but gauging plaster.
What kind of primer are you planning on using?
I have limited experience with plaster, but as I understand it you should use an oil-based primer on plaster.
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I assume by setting compound, you mean Durabond90. If so, perfect. Use a good primer, don't cheap out to save a couple bucks.