A general characteristic consequent to the loading of gut is that of requiring no particular twisting techniques since the high specific weight increase, by noticeably reducing the working diameter produces a remarkable decrease in the string's stiffness. The strings keep a smooth surface, in accordance with iconographic sources dating from the turn of the 17th century a good emblematic example of which is represented by the painter Evaristo Baschenish (1617-1677). He always depicted very curl strings on musical plucked and bowed instruments, and the length of string in excess and not in use, bundled up as though were of pliable cord (a detail not to be overlooked in our investigations; our modern strings, on the contrary, besides being impossible to bundle up in such a way without damage, they stick out of peg boxes as straight as pins) and also always depicted them having a smooth surface. Possible doubts about the accuracy in reproducing from life can be cleared by a painting in Palace Pisani-Moretta in Venice: besides the usual musical instruments whose smooth strings are clearly visible, at one side, lying on a tambour, is a tailor's spool where on the thread is a typical rope structure.

A second important indication coming from the 17th century iconography, is the colour of the lower registers strings. It must be said incidentally, that colour can not be taken on itself as a decisive confirmation of gut loading. In fact it is quite possible to increase the weight of the material even considerably, without changing the colour of strings to such an extent as to be noticeable on a painting. Besides, some dyeing processes in use in the 16th and 17th , especially for thin strings (see T. Mace and J. Dowland) aimed for purely aesthetic results. In any case, in the realm of the chromatically distinctions, iconography provides generous and important contributions, especially when taken in relation to other information available today. Thus low strings often appear to be blackish, brown or red coloured, in short, colours which are totally different from the natural colour of gut, and they begin to appear exactly where the acoustic shortcomings of plain gut would make themselves manifest.

The already mentioned C. Mouton's portrait, and that of the anonymous 17th century lutenist in the Kunsthalle, Hamburg are very good examples (25). Red bass strings, starting from the 6th course down, of apparently reduced diameters, suggest a use of colour which is not aesthetic, but simply a consequence of loading process, obtained perhaps with cinnabar, a heavy red mercury sulphide, which was an abundant raw material in some areas of central Italy, the same, in fact, where such a commercial type of bass strings were manufactured: the "pistoys" (9).

As far as bowed instruments are concerned, the best among many example available are two paintings from the second half of the 17th century by a Dutch painter in the German National Museum in Nuremberg. In these works a number of plucked and bowed instruments are depicted, probably life size, among which a (bass?) viola da gamba and a smaller one (soprano?) deserve special attention. Both instruments' 6th, 5th, 4th and 3rd strings, are fairly dark colour. The thickest string being almost black, while the two top ones, much lighter, are exactly the same colour of the frets.

Further details can be noticed, such as that they are perfectly smooth (on the bass viol's 6th string it is possible to see light been reflected), while the apparent increase in diameter does not follow the progression one would expect at all in a situation of equal working tension if gut strings of equal density were used. The violin also shows some very interesting aspects: while the first two strings are a light colour, the 3rd and 4th are a dark colour similar to those of the above described viola da gamba, bringing to mind J. Talbot's writing in the early 18th century: "...best strings are Roman 1st & 2nd of Venice catlins: 3rd & 4th best be finest & smoothest Lyons, all 4 differ in size...". Lyons, as known, were a renowned type of low register strings then available on the market. A confirmation of that anonymous painter's colour fidelity comes from the cittern, whose strings, again in accordance with J. Talbot, are a dirty yellow (brass) while the two top courses are grey (steel). Another example like this can be found in the wonderful painting Concerto in casa Lazzari (second half of the seventeenth century?) by Girolamo Martinelli located in Carpi (Italy). In this painting, Martinelli depicts the violone's third thorough sixth strings in a deep brown colour and the higher two strings in white. On the bass-violin depiced in the same painting, the bottom two basses are again brown, as in the violone, with the top two strings very light in colour and the second string nearly so.

The last example about violin came out from a paint of Rutilio Manetti, Siena 1624 year, (Dublin, National Gallery).