Get more confused all the time - I've used NHL5 Chaux Blanche as a white wash paint - just mixing straight with water, and it's worked OK.
My wife wanted to use Chalk paint to do some furniture and her friend has been using Chalk paint which is very expensive. She has searched on the Internet and they have basically said that you can make chalk paint by mixing ordinary emulsion with calcium carbonate.
I thought someone told me that Chaux Blanche NHL5 was Calcium Carbonate, so I suggested she tried that.
It's not working very well, so I assume my assumption that Chaux Blanche is Calcium Carbonate is wrong.
Can anyone put me right or does anyone know where you can buy Calcium Carbonate in France?
I think NHL's differ from chalks in clay content or impurities NHLs have. 5 is highest compression strength and fastest set time in no air or underwater applications. 5 is better for impermeable dense surfaces, 2 softer more porous surfaces like wood, chalky stones, slower set times when hydrated with water, or 3.5 is in the middle. Try 2 or 3.5. I think the set time or class has to do with amount of un-reacted calcium needing air and water to cure, hence 2 and 3.5.
Well chalk is a form of limestone CaCO3 and if thermally degraded will convert to CaOH + CO2. NHL is CaOH(lime) that when the limestone which has special impurities in it is cooked, it creates a lime that has extra chemicals in it that create a pozzolan effect. This is a secondary chemical reaction that makes the product easier to work with and in some cases more flexible and stronger. CaOH(hydrated) + CO2 = CaCO3, this is the limestone cycle which creates limestone plastered walls, but the paint you are talking about just has chalk in it, so no NHL anything, just add chalk to your favorite natural paint recipe and you get chalky paint, for what it's worth.
I been trying to get my head around the differences between NHL's and hydrates for a while. I talked to these guys below a while ago and their NHL's are pricey compared to hydrates. They have a ton of info on their site pertaining to pure NHLs and why they are worth the money: http://www.limes.us/contact/
So I called again to get it strait. You ask for a Chem-Engineer and you get a nice french man that tries hard to get you off the phone fast, but I would not let go until I got my answers These pure NHLs differ in set times by clay or "silica" burnt clay reactive content and are fast to set compared to hydrates that take forever to absorb air (CO2), therefore, St Aster says that hydraulics's (because they cure with water, no air, all 2, 3.5, 5 can be immersed in water, hydrates can not they need air to set). So the NHL 2, 3.5, 5 set times and compression strengths have to do with the "silica" burnt clay reaction cure time and pure burnt lime (or quicklime is the burnt lime term) cement content that brings up compression strength in 5 being the fastest cure and highest strength.
NHLs set faster and is "one" reason they are better than hydrates as plaster/stucco that take forever, and they resist water better. Hydrates are designed as mortar not walls and we need to add cements portland, etc) to get comparable strengths and desirable set times out of them. They use pure quicklime/clay no pozzolans that can be added to make AHL's (artificial hydraulic lime). Reason is they said no need they have a proven product throughout history and do not want to chance unwanted chemical reactions like with gypsum, fly-ash, OPC, etc, over time (efflorescence, or other complex chemistry that is not needed and risky). They said they do not need to un-pure their products with added cements (pozzolans) they flow well, set fast, come in three different strengths and set times. There are other lime manufactures of NHL's so shop around. Hydrates, "High Calcium Lime" is dolimitic lime and hydrate and comes from Europe (unlike types N and S made in the US) it is readily available cheap in the USA.
St Astier sells a lime paint they use a hydrate....don't ask me why he got me off the phone before I could ask, slower set time. All paint is, is a binder (any natural one will do, hydraulic, hydrate, pozzolan) iron oxide for color, water or oil as a transport. Just don't use an acrylic binder it's basically plastic like laytex not allowing the substrate to breath.
Keim has some Potassium Silicate paints that are great: http://www.keim.com/ I talked to them they no longer warranty their paints on mag board since in the last year the salt content from China mainly varies so too much....Some board are crushing on the job site you can push right through them he said. I was reading about them and got interested here. Anyone figures out how to DIY their paint let me know.