THE THREE YEAR LAW:
The Romans instituted strict construction regulations laws.
One of this strict rules was the use of lime putty aged no less then 3 years for any type of construction. This rules was instituted in part because of the possibility that some small lumps of quicklime may not have been fully hydrated. These small lumps may eventually expand and damage newly applied stucco or expand inside wall cavities. Our lime putty is screened during the slaking process as it migrates to the aging vats completely removing this issue.
It has been scientifically proven that slaked lime's crystalline size and structure changes through aging, and continues to do so indeterminately. Recent studies show that at about three years of age the crystalline structure of lime putty has changed in shape from prismatic to tabular. Much like fish scales, these particles have a benefitial effect on cohesion in stucco and plaster work. When the mortar is applied and smoothed out, these crystals line up in a flat overlapping fashion creating a strong cohesive bond. The cristals size distribution is also changed from an even size of micronic cristals to a more varied size distribution comprised of cristals of micronic to nanometric size increasing adhesion to the substrate it is applied on. This changes also improve the carbonation process. Aged lime has higher water retention properties and carbonation occurs faster and throuought the body of the mortar. The carbonation processin in mortar made with fresh lime putty starts at the exposed surface and slowly moves deeper into the masonry work. In aged lime mortar carbonation occurs from the extremities of the body of the mortar towards de center. T
The longer a lime putty is aged the "fatter" it becomes, increasing in adheision, cohesion, viscosity, workability, speed of carbonation and other beneficial factors.
Viscosity is extremely beneficial as it allows you to achieve a workable mix with minimal or no water addition. This minimizes shrinkage and cracking, frost resistance, speed of curing and many other beneficial results.
The smaller particle size of these crystals have a beneficial effect on adhesion/cohesion as these particles are better able to penetrate and bond to the aggregate and the substrate it is applied to.
I has been scientifically proven that the larger crystalline structure of hydrated lime (bag lime) when turned into a paste, remains unchanged even when left to age for long periods.
Here are some parameters for choosing which of Our lime putty is best for your specific job:
Crema di calce:
This lime putty is produced by slaking a hand selection of the whitest quicklime lumps, aged in open air pits and micronized prior to packaging.
Micronized lime putty aged 36 months or more:
Stucco and plaster finishes including Marmorino/ Venetian Plaster, Scagliola, fresco, lime paint, restoration work.
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Grassello:
Lime putty aged 12 to 24 months:
Stone and brick work, repairs, repointing, base coats, plasters and stucco, age for future use.
Lime putty aged 36 months or more:
Stone and brick work, repairs, repointing, base coats, plasters and stucco.
This aged grassello can also be filtered/sifted in order to be used for lime paint, fresco, restoration work and fine plaster finishes (Marmorino, Venetian Plaster, Scagliola, Tadelakt)
NOTE:
This lime putty may contain occasional small pieces of dried lime putty.
Occasionally small pieces of dried up lime fall off the machinery during the transfer of the slaked lime from the vats into the buckets (A very messy business)
These "lime aggregate" lumps are actually welcome in restorations where it resembles the underburnt/over burnt lime particles often contained in the original lime mortars.