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james 08-26-2007 11:30 PM

Quicklime vs. portland cement plaster
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.


Unofornaio 08-26-2007 11:44 PM

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 08-27-2007 06:49 AM

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 08-27-2007 10:33 AM

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 08-27-2007 11:06 AM

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.

maver 08-27-2007 02:33 PM

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.


james 08-28-2007 10:56 PM

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.

maver 08-29-2007 01:44 PM

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 08-30-2007 10:20 AM

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 08-30-2007 06:26 PM

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.

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