When you wish to make some glue, do thus: take some limed skins, and put them into lukewarm water to soak right through; wash and clean all the flesh tissue and dirt off them, and put them into clean water in a copper vessel to boil. Watch for when they come to the boil and begin to thicken, and strain them off either with a woven strainer or a cloth, otherwise they will burn, and then put in more water; repeat this two or three times, straining off until they are completely dissolved. If you cannot find limed skins, use unlimed ones, choosing the skin from the feet or the ears of oxen, and any skins that cannot be put to any other use or are of little value. If they are thick it does not matter; buffaloes and ewes are also good. Deal with them thus: take some quick-lime and put it into a pestle with some water and mix it until it is all dissolved; put the skins in this solution and leave them for a week, until every single hair has come off them. Then take them out, wash and clean them thoroughly and let them dry. Whenever you want to make glue, do as we have written above for you. But if you are in a hurry and have no lime, in order to soften the unlimed skins soak them and then put them on to boil for a short time; take them out and clean them well of any fat and flesh tissue and cut them up with a chopper so that they will be boiled more quickly; do not separate the pieces completely, but leave them joined together so that you will not be hindered when you come to strain them off. Boiling the skins like this you will obtain some glue. If you want to dry the glue, put the last of the glue alone on a low fire and let it boil until it coagulates, only watch it well as it may froth up a lot, and you must then let it sink down; you must therefore be present when it is boiling so that when it froths up you can take it off the fire and put it in a vessel of cold water so that it touches the bottom, in order to stop it rising. Put it back several times on to the fire until it coagulates, and then take it off and leave it to cool. Stretch a piece of string in a bow-saw, cut them into small pieces and leave them on a board for two or three days until they begin to harden; then pass string through them and hang them up in the air to dry completely, and keep them for when you want to lay gesso. See that you always prepare glue in cold weather, as it smells if the weather is hot, and you do not make such good progress.