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24|January 2020
Stone Restoration and
Maintenance Corner
Chemistry 101 – Part 2
which can be either wa- ter-based or solvent-based. Sealers give the best protec- tion against staining, etch- ing, wear, and most other negative issues. However, they have their own nega- tive issues, as well, such as a possibly significant change in the natural appearance of the material. Sealers most always take away from the natural beauty that stone and similar surfaces exude.
They can make the sur- face look plastic, which is exactly what takes place when it is applied. They can also discolor (turn yel- low), trap moisture (cloud up), and show scuffing and wear. In my book, sealers are pretty much for tex- tured stone only, and con- crete and terrazzo. You see, concrete guard products would be classified as seal- ers, too. Guard products, which are typically a high solids acrylic, can protect an acid stain on concrete, polished concrete, and pol- ished terrazzo from acid etching and other chemical contaminants. This is why guards are used in grocery stores and other similar high-traffic commercial applications.
Color Enhancers
Color enhancing prod- ucts are basically a pene- trating sealer, which is like a cross between a sealer and an impregnator. They don’t really leave a topi- cal coating, per se, but do fill the pores with resinous materials. These resins are
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what help bring out or en- hance the natural colors of the stone. Typically, color enhancing sealers are sol- vent-based but there are a few water-based color enhancers around. Just re- member that solvent-based products most always pene- trate faster and deeper than water-based products. Color enhancers are really only for more porous materials with lots of surface area like textured slate, flamed gran- ite, sandstone, and possibly a coarse-honed limestone, marble, or granite.
So let’s say you want pro- tection from liquid spills such as grease, oil and wa- ter-borne contaminants, but you have a polished material, or don’t want any appearance change. Well, this is where a true im- pregnator comes into play. Impregnators differ from sealers and color enhancers in that they use either a sol- vent or water to carry their fluorinated copolymer into the pore structure of the material. Once deposited, the carrier evaporates. They offer little to no appearance change and allow the stone to transpire water vapor (breathe) all while protect- ing the surface from liquid spills. They will not, how- ever, give complete pro- tection from acid etching on calcium-based materi- als, even though they can help minimize the damage. Impregnators are the staple for protection on polished kitchen countertops.
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Happy New Year to all you Slippery Rock readers out there!
As restoration and main- tenance professionals, we regularly deal with chem- icals. It only makes sense that we should have some basic chemistry knowledge, and perhaps a little bit more.
SoIsatdownwitha friend who also happens to be a bio-chemist with CoreChem.
John Rippetoe is one of those people who is a nat- ural-born teacher and loves sharing his knowledge of chemistry with others. I came to John with a list of topics that I thought would be relevant to our industry.
In Chemistry 101 Part 1, we covered the pH scale. In Part 2, we are going to cover other aspects of chemistry like densifiers, consolidators, impregna- tors and sealers, safety, and other issues.
Densifiers
Densifiers are typically used for concrete, terrazzo,
Bob Murrell
M3 Technologies
Photos by Bob Murrell
and even limestone. There are different types of liq- uid silicate hardeners, but mainly the sodium, potas- sium, and lithium densifi- ers are the most common. There are also colloidal products on the market, which simply drive mate- rials that harden into the surface.
All of these silicate den- sifiers react with the cal- cium hydroxide, which is a byproduct of cement hy- dration (water migrating up through and evaporating from the cement). Calcium hydroxide is actually not very hard and when it re- acts with carbon dioxide, it leaves behind a white pow- der on the surface, a pro- cess called dusting. When the densifier reacts with the calcium hydroxide, it forms calcium silicate hy- drate or CSH. CSH is what gives concrete much of its strength and hardness at the
Sandstone with Majestic Low Odor Impregnator applied. The test liquid beading up is Southern sweet tea.
surface, while preventing dusting.
Lithium silicate reacts with the calcium hydroxide faster and better than both the sodium and potassium silicate materials, without generating any hazardous waste water due to scrub- bing and removal. Lithium silicate densifiers are also easier to use – simply spray and massage into the sur- face with a microfiber ap- plicator, then allow to dry. There is no scrubbing or removal process.
Consolidators
Consolidators work simi- larly to colloidal densifiers by strengthening the stone through a bonding process. Many consolidators use a silicic ethyl ester to form silicon dioxide, which is
a glass-like material, and very hard. This SiO2, which has very similar properties to the original stone, re- places the lost cement of the stone due to weathering and moisture-related issues. These consolidators are very useful for deteriorating limestones and sandstones. Consolidators can also in- corporate an impregnator/ sealer so that once the mate- rial has been strengthened, it is also protected from liquid penetration and the elements.
Sealers
Speaking of protection from liquid penetration and the elements, let’s discuss the use of sealers, color en- hancers, and true impregna- tors. In my view, sealers are necessarily topical coatings,
Limestone floor after applying color enhancer—
Limestone floor before applying color enhancer. what a color difference! Sandstone — half with color enhancer applied.