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Lake of cochineal is violet; I've been lied to


Deo Lawson
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I made some lake from cochineal using sodium carbonate and potash alum, and it came out wonderfully violet. I want red, though.

I assume some additive is necessary to retain the red colour in alkali... or can the lake later be washed in an acidic solution to make it red again? I haven't tried that yet before.

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It’s been many years since I fiddled (pun) with cochineal. IIRC, the metal lake ion can shift the color. In any case, try aluminum salts for carmine. Also, read Michelman. I think the pH of the bath that links the metal ion is also important. 
 

Did you search thru old posts here on MN?

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The wood is basically yellow. With a nice transparent red you'll end up with an orange violin unless you apply a very thick layer. I think violet (between red and purple) is great for pulling the color over to red. You just need to figure out how much you need.

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7 hours ago, Deo Lawson said:

I made some lake from cochineal using sodium carbonate and potash alum, and it came out wonderfully violet. I want red, though.

I assume some additive is necessary to retain the red colour in alkali... or can the lake later be washed in an acidic solution to make it red again? I haven't tried that yet before.

Deo, there are good comments in the above posts worth taking note of.  Have you tried your lake in varnish yet?  Chances are that it will look somewhat less "wonderfully violet" once in a varnish. 

There are a number of factors that can influence what you end up with.  The order of extraction (i.e., alkali first versus acid first), pH values, molar strengths, temperature at various phases during the process etc..  If you are first extracting the dye from cochineal using sodium carbonate (as opposed to using potash alum), you could try acid modifying the dye bath.  This can make a difference, as can the particular lye itself.

If you ultimately decide you want a lake that is more red, try madder.

 

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2 hours ago, pbelin said:

Mine is quite purple when dry, but makes a beautiful dark red when I mix it into my varnish.

I suspect that is a pH effect. I think most resin/colophony varnishes used on string instruments are slightly acidic.

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I've tried mulling it into oil... some of the redness comes out but it's still very purple. I've found it useful for adding some vibrance to other madder-ish lakes I've made (some exotic hardwoods make great lakes, like padauk and bloodwood), although it's a still a bit of a shame since I have loads of the stuff and only a small amount is needed. Cochineal is remarkably powerful dyestuff! i wish I'd tried precipitating it with bicarb first before using sodium carbonate.

 

Washing some of the carmine lake with lemon juice had no effect. I guess the varnish itself has to have some acidic component to affect the colour of the lake, because it's no longer water soluble.

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2 hours ago, Deo Lawson said:

Washing some of the carmine lake with lemon juice had no effect. I guess the varnish itself has to have some acidic component to affect the colour of the lake, because it's no longer water soluble.

Am I understanding right that the lake you made is not able to be effected by water anymore?  If so, what does it attach itself to when added to other varnish components.  

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6 hours ago, Deo Lawson said:

Washing some of the carmine lake with lemon juice had no effect. I guess the varnish itself has to have some acidic component to affect the colour of the lake, because it's no longer water soluble.

Once you have created your lake pigment the colour is pretty much locked up.  I say "pretty much" as things will happen once it is mulled into an oil or varnish.  These pigments almost always fade, at least to some extent, and the mechanisms via which that happens seem complex.  Some purples will move to a red-brown or insipid pink or even to a semi opaque brown.  Photo bleaching and pH of the varnish will be players along with other factors including the degree to which you have washed your pigment thoroughly or not......

Changing the colour of your lake pigment is best achieved at the point where you are extracting the dye from your dyestuff material; i.e, prior to forming a precipitate.  I have mostly acid modified cochineal dye using citric acid, moving colour more towards a red.  I also occasionally use cream of tartar as a modifier as part of processes.  (This apparently dissociates into acid tartrate, tartrate, and potassium ions in water.)  Also using tin chloride mordant as opposed to alum will push things more towards a red, but, in my case, for some reason resulting in pigments that were less transparent.

Below are photos I happen to have of some cochineal based pigments that I have made.  Some have been happy accidents and some not...  (I say accidents because there are so many factors that influence what you end up with...)  Perhaps unwisely, I always initially make up relatively small samples until I have some idea of what is resulting in what.  At least this way you don't end up with "loads of stuff" that you will never end up using.

Cochineal.JPG

Cochineal standard.jpg

Cochineal variant.jpg

Cochineal close up.JPG

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I'm not sure anyone is interested, but all this talk of cochineal and madder inspires another of my obsessions--antique Central Asian tribal carpets.  This closeup of a c. 1880 Tekke Turkmen dowry mat demonstrates the difference between these materials in wool dyeing.   There are two distinct versions of cochineal in this piece (which is very rare), the darker magenta shade and the paler pink--the violet component.  Madder root is what they used to produce the rust-red color.  I don't know what material they used to produce apricot/orange, alas.  I am always struck by the use of aniline dyes in violin varnish.  Both the cochineal shades seen here, as well as the apricot, were later replaced by aniline dyes, which notoriously bleed and fade (on wool, anyway), and they look weirdly harsh/psychedelic/metallic.  They are anathema to oriental rug enthusiasts and their presence in a piece is like a back sound post crack for a rug collector, destroying most of the value of the item, but apparently they are fine in violin varnish.

TekkeRedsFront.thumb.JPG.8654b8fc15fad814090f83bf5182ab5f.JPG

Cochineal was introduced to Central Asia some time in the earlier 19th century, replacing the earlier insect-derived pigment, called "lac," which had been used for centuries in wool dyeing in Central Asia.  I wonder if anyone has used lac in violin varnish, and how it is different than cochineal.

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1 hour ago, palousian said:

Cochineal was introduced to Central Asia some time in the earlier 19th century, replacing the earlier insect-derived pigment, called "lac," which had been used for centuries in wool dyeing in Central Asia.  I wonder if anyone has used lac in violin varnish, and how it is different than cochineal.

Hi, There are examples of Mexican cochineal in Turkmen textiles as far back as the 16th century , it became pretty common in usage by the 17th century.  They probably had access to Armenian, Arrarat ,Polish  etc.. cochineal before that.

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On 5/19/2021 at 11:59 AM, JacksonMaberry said:

If it madders to you (pun again!), Go ahead and try it in some varnish. Alizarin rosinate precipitated with zinc sulfate (see my article in "The Scroll") comes out violet. But when cooked into oil - boom - it goes crimson.

Good luck and keep us informed!

I suspect the reason is that the oil is acidic. This is linseed oil? It can be very acid. Look at the information on the Natural Pigments website.

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I considered using powdered aniline dyes for a shellac finish but found them expensive. I also have an instrument on which the rear plate is colored by hardware store wood stain sandwiched between layers of shellac (not my doing!!!). It looks surprisingly good but doesn't have the deep, raw texture of traditional varnish—rather flat.

Does that count?

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