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Making Lake Pigments


Marcus Bretto
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Hello all! Starting to get into lake pigments!

So, to jump right in: when you’re making a lake pigment, what part of the process does pH have an impact on color? I’ve heard of people using acidic, neutral, and alkaline extractions for the dyestuff, but I’m curious as to how/if the ph of the extraction plays into the final pigment color. My thoughts are that it is really the pH of the final suspension that makes the biggest impact, but I just don’t know. Could you take dry, finished pigment and expose it to a medium of different pH to change the color? Will it keep this color upon drying off?
 

The long cook varnish I make has a very strong fire orange color just as it is, that darkens to shades of red in thicker layers, but I’ve been wanting to tone down the orange stage a bit and show a hint of bluish reds. I’m thinking about going with cochineal because if it’s natural tendency in that direction, but I’d love to be able to know how to adjust the color of the end product to the right side of the spectrum. Slightly more purples would probably get me exactly what I want.
 

I’ve heard multiple people say making a cochineal lake is tricky. What is the tricky part about it? What is critical to pay attention to? 
 

I’ll also make up some test samples with Joe Robson’s alizarin varnishes mixed with mine. I can’t foresee any problems, as the oil/resin ratios are the same, but if anyone thinks this is a bad idea let me know. Any recommendations for other things to try would be great, as well.

Thanks!

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The pH of whatever you use to extract colour from the dyestuff material (cochineal beetle, madder root etc.,) will have an influence on the final colour of the pigment.  There are other contributing factors including temperatures used at various times within the process, speed with which the precipitate is formed etc., that can also influence final colour.

Making a cochineal lake pigment doesn't seem any more difficult than making any other lake pigment.  (Madder can be more tricky.)  From what you describe, a cochineal lake pigment could give you what you want.

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2 hours ago, DoorMouse said:

1470915552_ScreenShot2020-05-15at2_38_54AM.thumb.png.e7f0e7a976fa439056bca06da905c09e.png

It seems that you forgot to indicate the amount of cochineal, I think it is important to avoid excess (or lack) of salts to avoid problems.  50g of alum and 50g of potassium seems a lot, so how much cochineal do you use and how much pigment you get? (more or less).

Thanks

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3 hours ago, Davide Sora said:

It seems that you forgot to indicate the amount of cochineal, I think it is important to avoid excess (or lack) of salts to avoid problems.  50g of alum and 50g of potassium seems a lot, so how much cochineal do you use and how much pigment you get? (more or less).

Thanks

I started with 1oz of cochineal and ended up with more pigment than an amateur like myself will likely ever need. 
I've only done this once and so far haven't had any problems with it.  It mixes easily and the color is stable so far. 
What do you think would be a more appropriate amount of alum and potassium?

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10 hours ago, DoorMouse said:

I started with 1oz of cochineal and ended up with more pigment than an amateur like myself will likely ever need. 
I've only done this once and so far haven't had any problems with it.  It mixes easily and the color is stable so far. 
What do you think would be a more appropriate amount of alum and potassium?

Mmm...1 oz.... should be about 28 grams...am I right? :)

You seem to have used a lot of extra alum and a lot of extra potassium. Usually, the amount of alum is equivalent to the amount of cochineal or madder root you use, and the potassium is about half that amount or even less. But don't take me too seriously, I'm not a chemist and I only rely on what I read and my limited experience (pigments are not something I make daily...).

Usually, the problem when you use too many chemicals is the residues that are not fixed or reacted and that must be washed away with the final washes, which might become quite long and boring. If an excess of alum remains, the pigment loses intensity because it works as a transparent extender, if traces of potassium remain, the color changes and the pigment becomes too reactive and perhaps unstable (the pH would not be neutral but basic).

But it looks like your pigment is OK, the color in the varnish also looks okay, and you've come up with such a large amount that you could put it up for sale.:D

Did you wash it with water to purify it?

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Thanks Davide, next time round I'll try the more appropriate chemical amounts.  
That's interesting that excess alum acts as an extender.  I wonder if I will get a more intense pigment by correcting the amounts.
Now that I think about it I'm not sure where I came up with the 50g figure.  
Neil Ertz was the inspiration for the method but I can't seem to find the original posting. 
It took around 5 or 6 washes to get the water clear.  

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  • 2 months later...
1 hour ago, Michael_Molnar said:

Experiment with a permanent modern pigment blend of PR 179 Perylene Maroon and PV 19 Quinacridone Violet.  These are on this color wheel. They won’t fade like cochineal. 

I haven't had the same problems with cochineal fading that a lot of people have mentioned.  I even kept a test strips with samples of different lakes mulled into varnish at the bottom of my light box for about a year, and the cochineal was one of the most stable.

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4 hours ago, violguy said:

I hope all will pardon my ignorance here, but would someone point me in the direction of the origen and definition of the word "lake" as it applies to pigments?

Thanks in advance to all who reply!

A lake is a dye that has been reacted with a mordant...usually a metallic salt ...which produces a colored crystal.

Joe

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From Wiki,

Etymology

The term "lake" is derived from the term lac, the secretions of the Indian wood insect Laccifer lacca (formerly known as the Coccus lacca).[3][4] It has the same root as the word lacquer, and comes originally from the Hindi word lakh, through the Arabic word lakk and the Persian word lak.[5]

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