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Limestone Plaster Source Question

 
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It says made from dolomite limestone, is this the limestone I need for making lime plaster and lime paint?  If not, where could I find an inexpensive source of hydrated lime in central Oklahoma?I know, dust safety means a breathing mask, lime handling safety means skin fully covered with clothing and (ugh) rubber gloves.  Along with building sand.  

If so, would I use one bag of limestone to one bag of sand with enough water to mold it into a ball?  If not, what ratio would I need?

How thick would it need to be to waterproof a cob wall?  1/2", 3/4", 1", thicker?

How many square feet of wall would one bag worth of lime mix cover at that thickness?

I can buy small quantities of pigments here. for lime, clay and milk paints.
 
master pollinator
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I don't know how different it would be with a dolomite-derived slaked lime. I would expect that magneisum hydroxide, being less alkaline, would not have as much of the desired properties that make lime work. You could mix a test batch (or six, with different aggregates and/or pozzolans) and see how you like it.
 
Chris Bright
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Phil Stevens wrote:I don't know how different it would be with a dolomite-derived slaked lime. I would expect that magneisum hydroxide, being less alkaline, would not have as much of the desired properties that make lime work. You could mix a test batch (or six, with different aggregates and/or pozzolans) and see how you like it.



Dolomite is magnesium rather than calcium?
 
Chris Bright
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Ah, dolomite is a mix of calcium, magnesium and oxygen.  How is that different from calcium oxides?  

CaMg(CO3)2

Testing, I guess.  Or find a different lime source.
 
Chris Bright
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1:3 Quicklime to aggregate, 3/8" down to dust.  

Either pound lime putty into dust and mix into sand or mix lime powder into sand and age at least three months.  Sand should be damp.  Don't add more water than necessary, should be thick and stiff, not runny.  Why am I thinking more like merange than custard?  Mix should stick to the bottom of a trowel.  If it runs of or slides of it's too wet or not mixed well enough.  If it's on top of the test trowel, flip the trowel over.  😎

Pay attention to safety, clothes, gloves, goggles, away from flammable stuff.  

At ~$4/bag, it just might be worth testing to see if it'll waterproof the way I want it to do.
 
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I'm a little concerned here. I just read a chapter called "Working with Lime" by Barbara Jones from the book "The Art of Natural Building". In it, she mentions that lime can be dangerous - it can explode if you add it to water, or was that vice versa? Sounds powerful. At the end of her chapter there are some recommended books: Building with Lime: A Practical Guide; Using Natural Finishes: Lime and Earth based Plasters; Lime in Building: A Practical Guide. Maybe you can get one of these from the library. She also says "Always use fresh hydrated lime, less than one month old."
 
Chris Bright
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denise ra wrote:I'm a little concerned here. I just read a chapter called "Working with Lime" by Barbara Jones from the book "The Art of Natural Building". In it, she mentions that lime can be dangerous - it can explode if you add it to water, or was that vice versa? Sounds powerful. At the end of her chapter there are some recommended books: Building with Lime: A Practical Guide; Using Natural Finishes: Lime and Earth based Plasters; Lime in Building: A Practical Guide. Maybe you can get one of these from the library. She also says "Always use fresh hydrated lime, less than one month old."



Yep, I am definitely keeping safety in mind, like full skin clothing, over the glasses goggles, rubber gloves (hated wearing gloves in chemistry and biology labs, but I wore latex then and I’ll wear rubber when ready).  Mask so I don’t breath the dust.  Wash any dust off skin immediately.  I do keep safety very much in mind.  

I saw add lime to damp sand, so I think it is add lime to measured water, be careful about temperature, don’t use glass or metal, but a 5gal bucket should have the flex to not explode.  Make on our concrete paving stone patio after removing weeds.  Be aware of hot hot it is getting, don’t want to have the bucket melt!

A reference site said age for at least 3 months.  You have less than 1 month.  Once lime plaster/paint is fully cured, it is as inert as limestone.
 
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