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Subject: "Lime Putty, Pit Lime, Quicklime, Slaked Lime"     Previous Topic | Next Topic
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"Lime Putty, Pit Lime, Quicklime, Slaked Lime"
 
Lime Putty is the main ingredient of the buon fresco painting.

Preparation of painting surfaces for fresco involves the application of plaster of increasingly finer texture.

The first step (which in nowadays mainly done by the factories) is the heating (calcination) of marble or limestone (calcium carbonate, CaCO3) at 800-900C to make porous lime (calcium oxide, CaO).


HEAT CaCO3(s) ----> CaO(s) CO2(g)

To form the plaster for fresco work, the lime is "slaked." The slaking process, which requires the addition of 2 or 3 molecules of water for each molecule of lime, yields calcium paste or lime putty, an aqueous gel of thin crystals of calcium hydroxide.

CaO(s) H2O(l) ----> Ca(OH)2(s) HEAT

Excess water acts as a lubricant so that the crystals slide easily over one another. Historically, lime was slaked in pits or troughs over a period of at least six months to obtain lime putty of the desired consistency. Artisans in Michelangelo's time use plaster aged for as long as ten years. Fresco plaster itself is made from the slaked lime and varying portions of sand or marble dust. Generally, walls are plastered with several layers of such fresco plaster in order of decreasing proportions and particle size of sand. Hardening of the fresco plaster on the wall includes several simultaneous physical and chemical process: the absorption of water into the wall, evaporation of water from the surface, and the carbonation of the slaked lime by carbon dioxide, CO

Ca(OH)2(s) CO2(g) ----> CaCO3(s) H2O(l)

Only high calcium lime putty should be used for fresco painting, the best would be lime putty produced from white marble. I have tried a wide variety of limes during the last 11 years and concluded that even the high calcium limestone is quite inferior to the white marble lime putty in it's plasticity and absorption of color.

The actual heating process also affects the quality of lime putty. Ideally Marble, Calcite (crystalline calcium carbonate) or Limestone for fresco should be burned in wood or electric kilns. Coal and gas burning kilns, the least expensive methods widely used for industrial production of hydrated limes, result in lime putty in which calcium hydroxide is partially changed to calcium sulfate (gypsum) which interferes with setting of the plaster consequently affecting the painting and color absorption.


"Marble, limestone and calcite are all forms of crystalline calcium carbonate, which is quarried and stacked in lime kilns, where it's carbon dioxide is driven off by heating. The result is quicklime or caustic lime (calcium oxide).

The stone fragments retain heir original shape throughout the burning process and only become white and a little lighter...

.. Quicklime is slaked with water, a process producing much heat during which the stones increase in volume and eventually disintegrate. The resulting slaked lime or calcium hydroxide is a voluminous white powder that can be packed in sacks and conveniently shipped to building sites. If during the slaking, however, more water is added than is necessary for the formation of calcium hydroxide, a pulp results that is stored in pits for as long as possible, and therefore is sometimes called pit lime.

Not all kinds of lime can be used for fresco painting. Lump hydraulic lime and dolomitic lime are quite unsuitable. Only white lime meets the necessary requirements. As quicklime, it should only contain 95% CaO and less then 5% magnesia."
Kurt Welhte "The Materials and Techniques of Painting" 1975 Prentice Hall Press.

The High Calcium Slaked Lime Putties are difficult to find locally (in USA), at the FrescoSchool.org we use imported from Italy "Calce Florentine" - High Calcium Lime putty sold by the www.FrescoShop.com at the www.TrueFresco.com/frescoshop


iLia Anossov (fresco)

www.FrescoSchool.org

learn fresco at http://FrescoSchool.org

fresco painting video tutorials: http://www.FrescoSchool.com

also visit

Fresco School Video Channel
http://youtube.com/FrescoSchool

Contemporary Fresco Gazette
http://trueFresco.Org
commission fresco or mural http://iLAdesigns.com

admin
____________________________
Contemporary Fresco Painting Resouce Center
http://TrueFresco.com


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alex33303
Member since 30-Oct-09
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30-Oct-09, 11:26 PM (PST)
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1. "painting"
In response to message #0
 
   Walls were the first painting supports. These mural paintings still exist today after twenty thousand years of protection deep inside ancient caves in India and France.

PAPYRUS: Papyrus is soaked, pressed and dried as strips of pith. it's a member of the sedge family. Papyrus was once abundant in Egypt and used by the Greeks and Romans as paper.

PAPER: Paper is also made of wood, cotton and linen. Linen is best, but cotton will do. Cotton paper is called rag 100%. The paper is glued throughout with an animal size. This is called vat sizing, and it is to be preferred. The papers I've found best are; a new paper hand-made called Twinrocker, Whatman, Strathmore, Lanaquarelle, Fabriano, Winsor & Newton, D'Arches and Waterford. They are all pH-neutral, vat and surface sized.


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cathyhastie
Member since 26-Nov-10
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09-Dec-10, 10:05 AM (PST)
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2. "RE: Lime Putty, Pit Lime, Quicklime, Slaked Lime"
In response to message #0
 
   What about "High Calcium Pebble Lime" in 1/4" to 0" size from Western Lime? aka Quicklime? Would this work? The checmical desription is below...
----
Hi Calcium Quicklime -- High calcium pebble lime as commercial grade, metallurgical grade and drinking water grade - available in Bulk and in Supersacks.

http://www.westernlime.com/products.php

I. Product and Company Information Reviewed on 08/07/09
Manufacturer: Western Lime Corporation Information: 800-433-0036 206 N. 6th Avenue
West Bend, WI 53095
Chemical Name Calcium Oxide
Chemical Family Alkaline earth oxide
Chemical Formula Mostly CaO
Molecular weight CaO = 56.08
Trade Names/Synonyms Quicklime, (Pebble)Lime, Calcium Oxide
Material Use Flux, Caustic agent, pH adjustment, absorption
II. Composition and Information on Ingredients
Component
CAS#
Exposure Limits
% by weight
Calcium Oxide
1305-78-8
OSHA PEL: 5 mg/m3 ACGH TLV: 2mg/m3
> 90%
Magnesium Oxide
1309-48-4
OSHA PEL: 15 mg/m3 ACGIH TLV: 10 mg/m3
< 2.0%
Crystalline Silica
14808-60-7
OSHA PEL: 10 mg/m3 (% SiO2 resp +2) ACGIH TLV: 0.025 mg/m3
N/A


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3. "RE: Lime Putty, Pit Lime, Quicklime, Slaked Lime"
In response to message #2
 
sure it will work better then type-s construction lime.
The question is what do you want to do? paint or test lime? (testing requires working knowlege and experience in fresco painting) Chemical formula is one thing - practice is another - you deal with many factors including "human factor" and purely scientific formula does not provide that. Keep in mind that Lime Corporation Tests are targeted for construction (building walls) not painting.

you need to slake it and age it to match placticity and "fresco friendliesness" of a proper aged pit lime.

if you want to put the work in and test, let me know results in a few years.

the extra cost that comes with proper lime will be far less the cost of trial and error.

hope that helps

learn fresco at http://FrescoSchool.org

fresco painting video tutorials: http://www.FrescoSchool.com

also visit

Fresco School Video Channel
http://youtube.com/FrescoSchool

Contemporary Fresco Gazette
http://trueFresco.Org
commission fresco or mural http://iLAdesigns.com

admin
____________________________
Contemporary Fresco Painting Resouce Center
http://TrueFresco.com


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