Quicklime vs. portland cement plaster

[james]

I am doing some research on different interior plasters and making plans for our indoor oven enclosure.

Can anyone help by explaining the difference between quicklime plaster and portland cement plaster? I have been reading various online resouces, and lime or cement-based plaster both sound like kiln fired limestone products that react with sand and water to make a product that sets hard -- unlike gypsom plaster that dries soft.

What are the different characteristics?

I did read that Venetian plaster is over 40% marble and sets with lime. Wow. No wonder it shines as so many levels, and is so hard.

Help.
James

[Unofornaio]

Re: Quickline vs. portland cement plaster

Depending on other additives (to increase strength) Limeplaster is generally weaker than a Portland mix. A portland mix should have lime added to it or have it contained in the pre-mixed bag.

[maver]

Re: Quickline vs. portland cement plaster

I made my own stucco, with a primarily portland stucco scratch coat and then a thin lime plaster finish. The lime really makes the stucco more workeable and sticky, so I added some to the scratch coat. The finish was white sand and lime, 2 to 1. When I deconstructed the oven during the move the scratch coat was rock hard, while the finish never really completely finished - I was always able to wipe a little sand off. I'm sure commercial products are better though. The lime is supposed to be nice in the finish as it is less prone to cracking - my finish coat never cracked until it was hit by the forklift. This sound right, Uno?

[james]

Re: Quickline vs. portland cement plaster

Thanks guys,
Is there a commercial lime plaster product you can buy? Is there a major brand name?
James

[james]

Re: Quickline vs. portland cement plaster

One more question. I know that portland cement based products undergo a chemical reaction that "transforms" the basic ingredients into something new, and I am pretty sure that gypsum plaster does not and simply dries hard.

What about lime plaster? Is there a chemical reaction and a curing period? Is that why lime plaster is a lot harder than gypsum?

Thanks again for the input on this one.
James

[maver]

Re: Quickline vs. portland cement plaster

Lime definitely has a curing period and a chemical reaction (it reacts to form limestone). Lime is slower to cure than portland and it does dry hard, but never as hard as portland cement which is why portland products have become the standard (also because lime is susceptible to acid rain, portland less so). I can't say much about a commercial product that is ready to mix as I used straight mason's lime with sand. I think some products would have lime in them - it makes the stucco more plastic and sticky. Here's a few websites I found by googling lime stucco:
this one has supplies (know nothing about them)
Lime Paint - lime stucco, lime plaster, marble and stucco application center
this one talks about the difference a little
Stucco Frequently Asked Questions - Buying Stucco

I also saw some descriptions of 'lime paint' which might be a way to achieve the look without a thick stucco buildup, but that's just from reading the websites - I'm not sure it's what you would want.

Marc

[james]

Re: Quicklime vs. portland cement plaster

Hey Marc,
This is a very interesting topic. I have found a handful of companies that import true "Italian" plaster -- in fact, one of the main producers is Baldini Vernaci in Lucca. If you drive from Florence, past Lucca to the coast, you go right past their factory.

There are a couple of primary types, including a Marmorino (powdered marble) plaster that is based on slaked lime; a Venetian plaster, that is based on an acrylik setting agent and very fine marble; and a more rustic marble/lime product that can be used both inside and outside. These are all color-in plasters that go up in 2-5 coats, where you burnish the final coats to compact the grains, and bring the marble powder to a polished finished.

I have ordered a couple of samples in different types and colors, along with my tool set.

I really can't wait for them to come -- the downstairs bath is the first test case.
James

[maver]

Re: Quicklime vs. portland cement plaster

James - what's in the tool set you ordered? I applied my stucco with a standard mason's trowel, but I wondered then if there was an easier tool to use.

[james]

Re: Quicklime vs. portland cement plaster

I am still waiting to get my tools, which are (guess what) also made in Italy. I ordered them with the product and color samples.

I think the tool has curved edges (not square like many drywall tools) and it is slightly concave. We'll see.

I have just about destroyed the second bath getting ready for the window and door, the Italian plaster, travertine floors and marble counters and shower walls. It take a lot of effort just getting back to scratch. The biggest hassle is the glue from the old wallpaper. I am using an enzyme glue remover, but it's taking a lot of time and it is very messy. Still, I don't want any residue up there for when I start plastering.

Once the samples get here, I will start a thread on Venetian Plaster -- let's see if someone else wants to do this technique on an oven enclosure.
James

[james]

Re: Quicklime vs. portland cement plaster

My first set of visual samples came today. These are little squares that show the different finishes and sample color combinations. I am getting pretty excited about this, but at the same time I am starting to get nervous. If I can make it work, the finish is just beautiful. If I can't do it (lacking in skill or patience), we don't want to go to the expense of having a pro do it.

The Venetian Plaster comes out looking like glass, with deep colors buried in the finish. They still use slaked lime and ground marble, along with modern binders. It is a very formal surface -- probably appropriate for a very high end hotel or restaurant. The Marmorino has the same basic ingredients, but it is a little rougher -- more appropriate for our house.

Next step is the get the samples of the material.

I have just about finished the destructo on the old bathroom. Ceramic tile on a concrete float. Nothing a sledge hammer and prybar can't fix. :-)

More to come on this.
James

[maver]

Re: Quicklime vs. portland cement plaster

James, I'm not sure this is appropriate for that bathroom or your locale, but I redid our master bath in our last house and I installed an electric heated floor system in the bathroom. As you are redoing the floor, it's a very simple process to include that upgrade and something to think about (better in a master bath where it gives you more use). It probably cost us about $300 for the electric mat plus the thermostat, but it was one of those little things that really makes you happy on a cool winter morning. It's on our must do list for our new house.

I'm going to look into these high end plaster systems for my redo of my oven - I'm planning stucco anyhow.

Marc

[james]

Re: Quicklime vs. portland cement plaster

Marc,
Nice idea. We're at the coast and it's always cold and damp. Towels never dry. We are thinking of a travertine floor, laid on hardibacker screwed down to the plywood subfloor/joist system.

Where does it fit? Do you have a URL?

This is why we need a General Building forum. :-)

James

[maver]

Re: Quicklime vs. portland cement plaster

If you are used to cold and damp, you'll really love heated tile. Want a dry towel? Just leave it on the floor a few hours!

This is the system I used (purchased off the shelf from Lowes)

SunTouch - Electric radiant heat mats

Here's another I found that you can order online

Radiant Heat Systems

You need the resistor (heater), a thermostat and minimal home electric wiring skills (or an electrician). The suntouch mat I purchased has a probe that is part of the mat - this interfaces with the thermostat to control the on/off cycling. The second URL includes a lower cost option where it is just the resistor wire without a mat - the mat helps fix the spacing but is not necessary - you could easily just lay the wire in thinset.

The resistor sits on top of the hardibacker and under thinset mortar. My install instructions indicated it's best to lay thinset mortar down under the hardibacker also prior to screwing it into the subfloor to reduce the chance of flex. The only tip that would have improved my installation would be to be sure to carve out a space in the hardibacker for anything thicker than the wire (such as the thermal probe) to avoid a raised area in the tile. If you are doing a formal tile that has precise edges you might even want to lay the wire in thinset first, then have a leveling coat of thinset above it that you set the tile in to be sure it's even.

I am not a contractor though, so please verify any of my advice before proceeding with it.

Marc

[james]

Re: Quicklime vs. portland cement plaster

I just forwarded this to Carrie. She grew up with plumbed-in towel rails. Thanks for the lead. More to come on this.
James

[Ken S]

Re: Quicklime vs. portland cement plaster

James Quick lime is a very dangerous product. The quick implies that it is alive. If you touch it it will burn your hands. When you add water to it to hydrate it, it will boil and reach a very high temp. The two limes that are safe to work with are hydraulic and hydrated limes. Hydraulic limes are used with gypsum products. Such as guaging plaster, or Keenes Cement. There is a niche for these products. They are not inferior to others, but different in type, nature and behavior. Hydrated lime is quick lime which has been slaked and partially dehydrated. Hydrated lime is what is used in high end finishes. It comes in type N low magnesium, and type s higher mag. The best is type N. You can slake it from one month to five years or more to increase its quality.. The difference between Venecianos and Marmorinos is size of aggregate. Basically 50 percent each and some binders. Portland cement with either limes chemically reacts and hardens in a short time. The hydrated lime reacts chemically with the marble and carbonizes to a stone like hardness in 28 days. Hence the draping off of building exteriors in Italy. Ciao Ken