This is taken from an old plaster book, Plastering - Plain and Decorative, William Miller ,originally published in 1897, but I have the George Bankart modified one, fourth edition, published in 1927. This book is not available so I am posting this note because I have never seen it mentioned in anyother fresco book.
" The following is taken from an old manuscript in the Soane Museum, dated 1699:-
'1. In painting the wall to make it endure the weather, you must grind colours with lime water, milk or whey , mixed in size.
2.The paste or plaster must be made with well-washed lime, mixed with powder of old rubbish stones. The lime must be often washed till finally all the salt is extracted, and all you work must be done in clear and dry weather.
3. To make the work endure, stick into the wall stumps of headed nails, about 3 to 6 inches asunder, and by this means you may preserve the plaster from peeling.
4. Then with the paste, plaster the walls a pretty thickness, letting it dry; but scratch the first coat with the point of your trowel longways and crossways, as soon as you have done laying on what plaster or paste you think fit, that the next plastering you lay upon it may take good key, and not come off or part from the first coat of plastering; and when the first coat is dry, plaster over it again with the thickness of half a barley-corn, very fine and smooth. Then, your colours being already prepared, work this last plastering over with the said colours in what draught or design you please - history, etc.- so will your painting unite and join fast to the plaster, and dry together as a perfect compost.
"NOTE.- Your first coat of plaster or paste must be very haired with ox-hair in it, or else your work will crack quite through the second coat of plastering; but in the second coat that is laid on of paste or plaster there must be no hair in it at all, but made thus; Mix or temper up with well-washed lime, fine powder of old stone (called finishing stuff), and sharp grit sand, as much as you shall have occasion for, to plaster over your first coat, and plaster it all very smooth and even, that no roughness, hills, or dales be seen nor scratches of your trowel. The best way is to float the second coat of plastering thus: After you have laid it all over the first coat with your trowel as even and as smooth as possible, you can then take a float made of wood, very smooth, and 1 ft. long and 7 - 8 in. wide; with a handle on the upper side of it put your hand in to float your work withal, and this will make your plastering to lie even; and lastly, with your trowel you may make the said plastering as smooth as can be.
5. In painting, be nimble and free; let your work be bold and strong; but be sure to be exact, for there is no alteration after the first painting, and therefore heighten your paint enough at first; you may deepen at pleasure.
6. All earthy colours are best, as the ochres, Spanish brown, terra-vert, and the like. Mineral colours are naught.
7. Lastly, let your pencils and brushes be long and soft, otherwise your work will not be smooth; let your colours be full, and flow freely from your pencil or brush; and let your design be perfect at first, for in this there is no alteration to be made."