Portland cement, mixed with sand and water, creates a very strong stucco, much harder and more brittle than like stuccos. Portland cement was invented in 1824 in England and named as such because its inventor, Joseph Aspdin, thought the cured concrete looked like Portland stone, which was a popular building material in England at the time. In 1824, a new invention changed the way stucco was used in buildings. Waxes, fats and oils were included to introduce water-repellent properties, sugary materials reduced the amount of water needed and slowed down the setting time, and alcohol acted as an air entrainer.Īll of these additives contributed to the strength and durability of historic stucco. Mud, clay, marble or brick dust, sawdust, animal blood or urine, eggs, keratin or gluesize (animal hooves and horns), varnish, wheat paste, sugar, salt, sodium silicate, alum, tallow, linseed oil, beeswax, wine, beer, or rye whiskey. According the National Park Service Preservation Brief 22, stucco sometimes contained any number of these unusual ingredients: Like lime plaster is made up of slaked lime (or a variety of other less typical natural binders, sand, and water) it was also given numerous additives to help it withstand the elements. So, you know what plaster is and what it isn’t now, right? So, what is stucco then? Stucco, sometimes called “render” by our neighbors across the pond, is an exterior coating that historically wasn’t much different from lime plasters. Personally, I prefer an old like plaster any day, even if most of the plastering I do these days is with gypsum. That doesn’t mean gypsum is a better material- simply that the building industry has gone to gypsum. Slowly but surely, gypsum has replaced lime for interior plaster, due to its faster drying time. Pre-1900 homes likely have all lime plaster walls, while homes in the first half of the 20th century may have walls with a scratch and brown coat of lime plaster and finish coat of gypsum. If your house was built before WWII, then your walls and ceiling are usually a combination these two materials. Lime plasters, however, can excel outdoors under most weather conditions, and with certain additives to ensure they have a long useful life. Gypsum plasters are interior plasters, typically not meant for exterior use because they do not do well with repeated exposure to water. It typically didn’t require horsehair to strengthen it either like lime plasters do. Unlike lime plaster, gypsum cures fast (only a few days) and sets even faster, which is why we make casts for broken limbs with the stuff. Most gypsum plaster came from Paris, and so the name stuck. It got the nickname because in the 1700s, Paris was built on top of some of the largest natural gypsum deposits in the world at the time.
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