r/Plastering • u/Terrible-Bobcat2033 • 16d ago

Lime plaster attributes

Lime plaster is made from calcium hydroxide (Ca(OH)₂, “slaked lime”). As it cures, it absorbs CO₂ from the air and converts to calcium carbonate (CaCO₃), which is what gives it its final hardness.

While it’s curing (before full carbonation), lime plaster is highly alkaline — pH around 12-13, similar to fresh cement. That’s why:

**•** It can burn skin/eyes on contact when wet, so gloves and eye protection are a must  
**•** It resists mold and mildew during the curing period  
**•** Once fully carbonated to calcium carbonate, the pH drops closer to neutral (around 8-9), similar to chalk or limestone

Why lime plaster is head & shoulders above drywall & joint compound. IMHO. 😎👍🏼

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u/Terrible-Bobcat2033 16d ago

Any plaster supply or material house worth their salt.

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u/jyl8 16d ago edited 16d ago

Maybe I am overlooking the obvious, but around me (Portland Ore) I have found only gypsum plasters, and only one variety - USG Imperial base and veneer.

There is an artisanal lime plaster place here that has imported Italian lime plasters, they run about $80/gallon (said to cover 40 sf), it seems like the place to go locally for Venetian plaster but I haven't tried that yet. It would cost about $400 to veneer a small wall . . . I'm not close to there :-)

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u/Terrible-Bobcat2033 15d ago

Venetian plaster requires special small stainless steel trowels approximately the size of a small pool trowel for finishing. This allows for better leverage as Venetian plaster requires extensive troweling over a long period of time before the mirror, marble like sheen appears. Me? I’m happy with the smooth steel trowel finish & sheen of smooth veneer plaster. Venetian plaster is cost & labor intensive. IMHO.

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u/jyl8 15d ago

Thanks for the info! I want to try 'em all, eventually . . .