Making and Knowing
A minimal edition of BnF Ms Fr 640 in English Translation

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To make varnish

Take one pound of linseed oil, and then put it in a pot of earth mixed with a breadcrust and three onions, and put it on a charcoal fire, and you will cook it on a low fire, and let it boil for the space of five hours. You will take half an ounce of flour glue, and will make it boil just as before, and stir continuously with a spoon. And then afterwards, you will add two ounces of well—pounded sandarac to it, and will do so as above. And then afterwards, you will take mastic and gum arabic, two ounces of each, both well pounded, and will put everything together, and will have it boil, always stirring, for the space of five hours. And then you will add rock alum, two ounces, and then you will make it boil. And if you add two ounces of gum arabic to it, if you see that they are not cooked enough, have it cook more on a low

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fire until it is cooked enough. And strain it through a cloth that is compact enough. And when you have strained it, leave it to cool a little. And if you see that it is so thick that you cannot strain it, you will add a little of that oil and will make it better.