From "For Chusing of Lute-strings" by John Dowland, in Varietie of Lute Lessons, Robert Dowland, 1610:
… Ordinarily therefore wee choose Lute-strings by the freshnesse, or new-making: the which appeares unto us by their cleere and oylinesse, as they lye in the Boxe or bundle; yet herein we are often deceived, for Oyle at any time will make strings looke cleere, and therefore this tricke is too too commonly used to them when they are old.
Now because Trebles are the principall strings we need to get, choose them of a faire and cleere whitish gray, or ash-colour, and take one of the knots in your hand, but let it not be too small, for they give no sound, besides they will be either rotten for lacke of substance, or extreame false. Also open the bouts of one of the ends of the Knot, and then hold it up against the light, and looke that it be round and smooth: but if you discerne it to be curlie, as the thread of a curled Cypris, or horse hayre, (which you may as well feele as see) then refuse them, although they be both cleere and strong, because those strings were not well twisted, and therefore will never be true on the Instrument. For trying the strength of these strings, some doe set the top of their fore or middle finger on one of the ends of the Knot, which if they finde stiffe, they hould them then as good; but if it bend as wee say, through a dankish weaknesse, then they are not strong. Some againe doe take the end of the string between their teeth, and they plucke it, and thereby if it breake faseld at the end, then it is strong, but if it break stubbed then it is weake. This Rule also is houlden for the breaking of a string between the hands. The best way, is to plucke out an end of the string (if the seller will suffer you, if hee will not assure your selfe that those strings which he sheweth you are old or mingled,) and then looke for the cleerenesse and faults before spoken, as also for faseling with little hayres. And againe looke amongst the boutes, at one endof the Knot, that the string be not parted, I meane one peece great and another small, then draw it hard betweene your hands, to try the strength, which done, hould it up againe against the light betweene your hands, and marke whether it be cleere as before; if it be not but looke muddie, as a browne thread, such strings are old, and have been rubbed over with oyle to make them looke cleere. This choosing of strings is not alone for Trebles [1st course], but also for small and great Meanes [2nd and 3rd courses]: greater strings though they be ould are better to be borne withall, so the colour be good, but if they be fresh and new they will be cleere against the light, though their colour be blackish.
Now again some old strings will hould well the stretching betweene your hands, yet when you set them on the Instrument they will sticke, (and rise by starts) in the Nut, and there breake, even in the tuning: the best remedy when the strings sticke so, is to rub the little nickes of the Nut, (in which the string slides) with a little Oyle, Waxe, or black lead. If you desire to choose stringes that are not false, that the maker cannot promise you; but there is a rule for the knowledge thereof by sight after the string is drawn out, which being it is so ordinarie and so well knowne, I hould it not fit to trouble you with the relation. Some strings there are which are coloured, out of which choose the lightest colours, viz. Among Green choose the Sea-water, of Red the Carnation, and of Blew the Watchet.
Now these strings as they are of two sorts, viz. Great and Small: so either sort is pact up in sundry kindes, to wit, the one sort of smaller strings (which come from Rome and other parts of Italy) are bound up by certaine Dozens in bundels; these are very good if they be new, if not, their strength doth soone decay: the other sort are pact up in Boxes, and come out of Germany: of these, those strings which come from Monnekin and Mildorpe, are and continue the best. Likewise there is a kinde of strings of a more fuller and larger sort then ordinary (which we call Gansars). [see paragraph 4 of
Federico Marincola's translation of Capirola's instructions] These strings for the sizes of the great and small Meanes, are very good, but the Trebles are not strong. Yet also there is another sort of the smaller strings, which are made at Livornio in Tuscanio: these strings are rolled up round together, as if they were a companie of horse hayres. These are good if they be new, but they are but halfe Knots. Note there is some store of these come hither lately, and are here made up, and passe for whole Knots. For the greater sorts or Base strings, some are made at Nurenburge, and also at Straesburge, and bound up onely in knots like other strings. These strings are excellent, if they be new, if not, they fall out starke false. The best strings of this kinde are double knots joyned together, and are made at Bologna in Lumbardie, and from thence are sent to Venice: from which place they are transported to the Martes, and therefore commonly called Venice Catlines. The best time for the Marchant is to provide his strings at Michaelmas, for then the string-makers bring their best strings which were made in the Summer to Franckford, and Lypzig Martes. Contrarily at Easter they bring their Winter strings, which are not so good.