Photos from left to right:
Chamisa/Rabbitbrush lake in process.
Chamisa flowering in Central Oregon
Chamisa Lake pigment on paper made from dried Chamisa flowers
Lake pigment primary trio: Privet berry, Madder root, Marigold flower
Madder lake with wilting Amaranth stalks
Madder lake pigment made three ways from one dye bath
Sappanwood chalk lake
Sappanwood lake without chalk
Mulling Chamisa lake pigment into a watercolor paint
Privet and Chamisa lake pigments drying, or blue moon over field of yellow flowers
Lake pigment settling
Privet lake still foaming
Do you remember how I explained the difference between a dye and a pigment in the last
blog post titled What Is Ink? If not, here is a quick review. A dye is a colored liquid made from infusing plants or other biological material into a liquid, similar to making tea. In a dye the color cannot be separated from the liquid. The colorant is dissolved in the liquid creating an even transparent color. A pigment, on the other hand, is a colored particle that does not dissolve in water. A lake* pigment is made when one transforms a soluble dye into an insoluble pigment.
Why would an artist ever want to do that? Well, pigments have some advantages over dyes. First off, once a pigment is dry it is shelf stable. That marigold dye you made will probably go moldy within a week, but if you make it into a lake pigment you can store it in a little jar indefinitely. The biggest advantage is that pigments can be mixed with different binders to create a wide variety of artist materials. You want to make a marigold pigment pastel? No problem. Or maybe a marigold lake watercolor paint, great. Oh never mind, you decided to make a marigold lake wax crayon instead. All of this is possible with a lake pigment and the appropriate binder. Excited yet?
Okay, so how do you transform a dye into a pigment? I'll lay out the basic theory so that you can troubleshoot your own recipes. You need three ingredients: a plant dye, alum (I use potassium aluminum sulfate or potassium alum), and an alkalizer (soda ash or calcium carbonate). When you add the alum it will bond to the color molecules in the dye. The magic trick is that alum is only soluble in an acidic solution, and alum is slightly acidic so it will be soluble until you add the alkalizer. Once the alkalizer is added the alum comes out of solution, becoming a solid again, and it drags the color molecule along with it. This solid pigment, made up of alum and the colorant, can then be filtered out of the remaining dye solution with a coffee filter or fine cloth and dried for storage.
How much alum do you add? The general rule of thumb is 10 grams of alum per liter of dye. However it really isn't about the volume of your dye but about how concentrated it is. If you have a weak dye add less, for a strong dye add more. I always dissolve my alum in a separate clear jar with hot water so I know it is all dissolved before I add it to the dye. Stir a bit then add the alkalizer. The rule of thumb for soda ash is 5 grams per liter of dye, or half the amount of alum you used. Again, I always dissolve the soda ash separately in a jar with hot water before adding it to the dye. It is much harder to see if those little crystals have dissolved once they are in the murky dye. The amount of water you use is irrelevant because the pigment will eventually be separated out from the water. Once you add the alkalizer stir well and then wait. You should start to see a soft cloud-like mass settling in the dye (use a clear container). This can take a while. Watch for a band of paler liquid immerging at the top of the dye.
Honestly, if I wrote out all the tips, tricks, and variations on this process this post would be a book. I'm giving you the laking process in brief, but I recommend looking for a class if you haven't tried this before. It will save you a lot of trial and error time. There is a fix for almost everything that might "go wrong" if you have someone practiced to guide you through it. And once you get those details down you will be free to improvise your own recipes and variations at will.
I will add one more tip though. You know how kids sometimes make those acid + base volcano projects that result in a foaming fountain? Well, the laking process also uses an acid and a base. There can be a lot of foaming, particularly if your dye solution is still warm/hot. Leave plenty of space in the reaction container for foaming or put a tray underneath to catch any overflow. If you don't get much foaming don't worry. It doesn't necessarily mean the reaction didn't work.
Although the lake pigment is shelf stable once dry it is still susceptible to fading in UV light, just like the dye would have been. The alum helps stabilize it, but can only do so much. Store your lake pigments away from UV light to preserve their vibrancy.
*Why is it called a lake pigment? The name comes from the insect dye lac. Click here to see lac. Lake referred first to the dyestuff and dye, then later to a dark red pigment made from it. Eventually the name lake referred to the entire class of pigments made by turning a dye into a pigment. It actually has nothing to do with the kind of lakes you might swim in.