[split] Jorge's Retracer Thread: darker ink, retracing of text and drawings

[Jorge_Stolfi]

I see it the same way as in the example.

How difficult it is to maintain the same ink colour over the years. And these were professionals. But I don't see any difference in the VM. The date is on the right. Lisa will know for sure if it's the same handwriting.
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As you can see, the darkness of the ink varies a lot from line to line.  The hue, however, is the same for any given darkness, over the years, because it is the color of the iron-tannin complex that is the coloring substance in iron-gall ink.  

That gamut of colors is characteristic of inks and paints based on transparent dyes. Namely, as the layer gets thicker, the apparent color gets darker and the hue shifts, until the thing is black.  Like tea changes from light yellow to dark red-orange and eventually to black as the thickness x concentration increases. 

That is different from inks and paints that are suspensions of solid pigments in a binder, like watercolors, gouache (tempera), oil paints, frescoes, etc.  With these, as the layer of paint becomes thicker, the color tends "in a straight line" to the pigment's color; and, above a certain thickness, the color does not change any more.   If you dilute ketchup in water, dilute solutions will look pink against a white wall; but above a certain concentration x thickness the color will remain the same tomato red, no matter how thick you make it.  Even against a black wall.

I mentioned before some of the reasons why I believe that the ink in the VMS is not iron-gall ink but some watercolor based on an iron pigment like sienna.  The way its color changes with thickness is another reason.  The first Restorer must have tried his best to match the ink type and color, just like a modern painting restorer would.  Later Retracers were not so careful. One of them may even have used iron-gall ink instead.   

All the best, --stolfi