Dinie Gootjes

Hi Pierre,

This salon is incredibly interesting. A lot of it went above my head, but enough remained to keep me reading, despite the fact that I had 'better' things to do. If before this you were afraid that you were taking a free ride, be assured that you now have built up a big credit .

You have hinted that indigo is a special case. I have read that it does not really penetrate the fiber, but forms a kind of coating on the outside. That was why jeans fade so well and why a green made by dyeing blue over yellow, tends to become yellowish. Indigo rubs off. Is this correct? Could you go into the blues a bit for us?

Dinie Gootjes

Pierre Galafassi

Hi Dinie,
Thanks for the flowers.
It is true that when applied on cotton denim, indigo does not penetrate deeply into the fibre and quite some indigo pigment even does sit on the surface of the fibre. By "stone washing" (industrial rubbing) the outer layers of the cotton denim fibers are in part rubbed away, showing the white fiber and giving the much sought after jeans look. The poor penetration of indigo into cotton is due to the strong tendency of its soluble reduced (yellow) form for oxidation and its premature precipitation in form of the insoluble blue pigment. But this tendency is accentuated on purpose by the specific "dip and air" machines used for dyeing of denim yarn.

When dyeing wool skeins for rugs, the dyer does indeed his very best to avoid premature precipitation and surface dyeing and (if he is competent) he does succeed , partly. So rubbing-off of indigo surface pigment is much less important on wool rugs than on cotton. I might be wrong, but i believe that an antique natural green is more likely to become bluer over time, due to the fading of the rather poor light fast yellow (indigo is very lightfast), than getting more yellow over time due to rubbing off of indigo.
Best regards
Pierre

Steve Price

Hi Pierre

My observation is that the greens in what appear to be naturally dyed old rugs usually have bits of yellow scattered here and there, almost always in areas most subject to abrasion. I don't recall seeing spots of blue in green areas. Two points arise from these observations:
1. Unless something else that hasn't occurred to me is going on, abrasion of surface indigo in natural greens is significant. Less significant than on my blue jeans? No doubt, yes. But significant.
2. The yellows probably do fade on natural greens that I've seen, but they remain recognizably yellow. Of course, if I've seen any rugs in which the yellow is faded to white, I wouldn't know that the blue had originally been green and those wouldn't enter my mind's database of rugs with natural green in the palette.

Regards

Steve Price

Pierre Galafassi

Hi Steve,
Your observation indeed is a strong indication that there was large "surface indigo" or at least "poorly diffused indigo" on the pieces concerned. Was it the rule, a very frequent occurrence or the exception? I really can't tell. As you know, Indigo was and still is a rather difficult dye to use and my best guess was that mistakes probably did happen quite frequently, since the very sensitive pH and ox-red potential were measured by the smell-, taste and "greeness" of the dye-bath. (I must have buried somewhere a few fascinating old indigo dyeing processes and will mail them if i found them).

There seems to be a rare case of unanimity among rug experts, that even nomads often asked settled specialists to dye their wool blue (unlike all other shades). The high price of the mostly imported dye was probably a strong incentive for not wasting it in trials and errors. The dyeing remained a mystery for most people even in pre-industrial Europe. Still today, in Germany, the expression "Blau faerben" designates a rather mysterious affair, borderline to witchcraft or even to the source of wealth of (European) politicians.
best regards
Pierre

Steve Price

Hi Pierre

Your question raises thoughts that disturb my complacency.

About the yellow patches in green area of old rugs, you ask, "Is it common?" I use it as a diagnostic sign of a natural green, and generally don't think a green is natural unless it shows this. It's more than common, it's universal. Obviously, since I use it as a way of defining a green as natural, every green that I judge to be natural will show it. The conclusion is embedded in the assumption.

I'm reminded of a "Peanuts" cartoon that I keep on the bulletin board in my office. Charlie Brown says, "Something that I was sure would happen, didn't happen. What should I do?" Linus answers, "Well, you could admit you were wrong." Charlie Brown responds with "Besides that, I mean."

The bottom line is that I see it a lot, but may treat its absence as a sign that the green I'm looking at is synthetic.



Regards

Steve Price

Pierre Galafassi

Well Steve, my answer related really only to the occurrence of yellow areas which seem to have been created by abrasion of the blue, probably frequent on prayer rugs, runners or civil servants pile seat covers.

As for yellow-blue dichroism of a few knots each or of full rows in a green area, it can be explained by the very strong abrash typical of indigo dyeing. (The natural yellows are much less prone to un-level dyeing than indigo and our eye is very sensitive to even small shade changes on the blue-yellow shade axis.)

So my question was : Is blue abrasion very frequent ?
Surely green abrash must be extremely frequent, just as is blue abrash (except perhaps in the darkest navy- surmet shades).
regards
Pierre

Steve Price

Hi Pierre

Actually, I see it most often on soumak. Maybe that's because there's one soumak cargo bag that I see nearly first thing every morning. Here's a direct scan of part of one face:



The part that looks light blue on my monitor is distinctly green, with flecks of yellow showing through (they don't look very yellow on my monitor). The part that looks dark blue is dark blue, and the flecks peeping through are white. The yarn segments that are yellow on the surface are green on their undersides. That is, if you rotate that yarn around its long axis, it's green on one side, green with yellow flecks on the other.

Regards

Steve Price

Steve Pendleton

>About the yellow patches in green area of old rugs, you ask, "Is it common?" I use it as a diagnostic sign of a natural green, and generally don't think a green is natural unless it shows this.

"Blue-yellow separation of green in dyed wool is also the result of the special character of indigo as a dye. If the wool is first dyed yellow and then overlaid, so to speak, with the indigo blue to make green, after some time the abrash effect is especially evident. In places where a thicker layer of indigo has occurred, the material appears to be almost blue. In places where the indigo has been worn away, it is more yellow. If the yarn has been dyed first blue and then yellow, perhaps with dyers weed, then the separation into blue and yellow is less frequently found or does not occur at all. If the yellow dyestuff is less lightfast, then there is no separation but only a shift in one direction: Due to fading of the yellow, the green becomes bluer. Abrash can occur, however, if the fading of the yellow is uneven due to varied exposure to light."

-- Harald Bohmer, Koekboya, pg 271, bold emphasis added

On page 103, Bohmer prefers 'indigo then mordant then yellow' "because it is easier to control and regulate."

I've seen Kurdish piece with an even green that I'd bet is natural. I've seen a Yalameh piece with a variegated green that I infer is double-dyed indigo and a synthetic yellow.

Steve Pendleton

Pierre Galafassi

Hi Steve,
I would never contradict Dr Boehmer, he has such a huge field experience in natural dyes, that I can only dream about it . I represent the competition (synthetic dyes) remember.

From a chemist's point of view too; it makes more sense to dye indigo first, investing all the time and skills necessary to get the dye as level as possible and achieve the right shade. Once this long process is achieved, one does a thorough rinsing and performs a quick(er) mordant dyeing with the yellow. To do the contrary would put the dyer in front of a "no-win" choice:
- either to expose the fragile yellow chromophore to the long indigo process (which, remember, is run under pretty hard reductive and alkaline conditions and has to be repeated several times for saturated shades.)
- or to run a "quick and dirty" indigo process which would surely yield a rather poor, extremely unlevel and weak shade.

I would like to remember Steve Price's previous observation, that in green shades he always observed yellow patches or knots, never blue ones. This makes a lot of sense to me (even without speculating a rubbing off of surface dyed indigo): Both the yellow dye and its alum- (or tannin-) mordant have good leveling properties, the dye is homogeneously distributed on the yarn (similar concentration of yellow everywhere). Indigo is nearly sure to be un-level (more if it is dyed after the yellow due to the hurried dyeing, but even when it is dyed first).
Thus, your yarn will have various shades of green (yellow is always present) and the occasional pure yellow places, wherever indigo is fully absent. Pure indigo blue spots are logically very rare!

regards
Pierre

Dinie Gootjes

Hi Pierre, Steve, Steve and All,

I had a few pictures of a green changing to blue ready, when in the meantime the discussion has moved forward. I will still show the pictures, just as an illustration of what Pierre is saying. They are of a Yalameh which I have shown before on T'Tek. On the back there is an irregular bluish green, with what looks like some blue spotting . On the front the colour is a middle blue, with hardly a trace of green. It is the outlining of the botehs and the first diagonal above them.





The yellow is clearly darker on the back than on the front, where it is a soft buttery tint. I have always assumed that the same yellow was used for the green. The blues and green are true to life on my monitor, unlike the over-enthusiastic red .

Dinie