im trying to \stay with all organic materials but i know with our substrates there has to be some 5 percent binder but i researched the pozzolans they used in roman times and there is many diff types of them specially for pools that make lime or portland cements more cementious / harder especially helping the ozone layer buy adding more organic material with the plaster therefore reducing the amount of carbon released in the atmosphere. so the more recyclable material that s mixed with your plaster actually helps the environment which im trying to achieve especially because i sick of smelling inert gases!!!oil or acrylic but just trying to take vitruvius ideals and just dont take what history gives us but build upon them (using the right and left brain) sorry for getting to remorse! but im a firm believer in recycling. such as the magnesium marble that sculptari relates to that the aggregates used are simple light weight sawdust that achieve the same results.. and 10 times harder interesting but stilll researching ohh and and i used hide glue and it works the same but still finding cheaper distributors and yes just lime and marble dust over our substrates prove to not bind to the wall without glue or acrylic resin because lime plaster is generally trowelled over lime or caustic substrates burning into each layer but the 2nd dna coat proves to give the same mottling affect as so called venetian plaster/ polished stone... the pozzolan/lime chemical reaction is a proven fact just look at the pantheon parthenon i forget in rome still standing .. hey check this out lassenite lassen county california they sent me a free bag of pozzolan tan in color made of 1000 s of year old lake bed fossils and volcanic ash free to test read ther website lime pozz reaction used to make the hoover damn! or fly ash but that black or gray would b good for dark color plaster i would think. anyone interested