overmarbling

An overmarble or double marble is created by printing over the top of one marbled design with a second print, allowing the two to commingle. These can be very beautiful and subtle designs, often relying on a lot of negative space or transparency in the second pattern for the first to peek through. Overmarbling can be risky- the second design can save a shabby print, or ruin an excellent print. Below is a lovely example by Don Guyot held by the University of Washington Libraries Special Collections, showing the first pattern alone and with the second laid over top:

 Don Guyot double marble, University of Washington Libraries, Special Collections

Don Guyot double marble, University of Washington Libraries, Special Collections

I’ve read that overmarbling requires a second mordanting between the first and second prints, but I’ve have mixed results when overmarbling fabric. Continuing with my experiments into alum and alum quantity, I decided to test the assertion that a second mordanting is required for a double print.

Process

Using 1.5 teaspoons alum per pint warm water, I pre-mordanted paper and pressed it between blotting papers for 1 hour. After the first print with watercolor paints, the paper was rinsed, dried, and pressed again. Sample A was printed with a second design immediately, and Sample B was given a secondary mordanting and pressing before printing again.

 overmarble with watercolor paints

overmarble with watercolor paints

  • A Preliminary mordanting only

  • B Preliminary mordanting & secondary mordanting prior to second print

As you can see, Sample B was able to absorb and retain much more of the second print than Sample A. While both are reasonably attractive designs, it is much preferable to have the control offered by a second mordanting in order to strategize the transparency and negative space in the second design.

It seems that, because alum readily bonds permanently with other compounds, it fixes a thin layer of paint and size to the paper with the first print. Gentle washing rinses off the excess, but even in areas of negative space a film of carrageenan remains bonded to the alum. This will hinder the second print from bonding, leaving only a faint image.

My recommendation: After the first print, gently rinse, dry, re-mordant, and press before each subsequent print. Follow a recipe when mixing your mordant solution to avoid overly acidifying your paper. I’ve made overmarbled designs four prints deep with this technique. With each re-wetting the paper is more likely to become damaged, cockled, or generally misbehave, so apply mordant and take prints very carefully.

Overmarbling Fabric

Double prints or double sided prints can be made on fabric in the same way. A double sided print on a light, diaphanous fabric has the lovely appearance of a double marble. Sometimes the second print will transfer beautifully without re-mordanting, particularly if it’s printed on the reverse of the fabric, which did not come into direct contact with the size. But to avoid the frustration of a sadly pale print, I recommend re-mordanting between prints on fabric as well as paper.

Remember, wet fabric cannot absorb a marbled print, it must be thoroughly dried and ironed between prints.

 double sided silk scarf

double sided silk scarf

Note: Suminagashi

If you are creating suminagashi designs on washi, mordanting is not needed for the first or any subsequent prints! Washi is so absorbent it doesn’t require alum to fix the pattern. However, suminagashi on fabric does require the same mordanting steps as above.

maya blue recipe

After discussing Indigo as Pigment, I’ve had a lot of requests to share the process for making Maya blue. This recipe is based on the research of Michel Garcia, whose Natural Dye Workshop DVD series I recommend. To make Maya blue pigment at home, only two ingredients and a few tools are required.

  • Botanical indigo powder: This can be store-bought or home processed, and must be thoroughly dry and finely ground.

  • Clay substrate: Sepiolite, palygorskite or attapulgite will absorb the indigo when heated. You can purchase small jars here, or larger amounts here. If your clay is granulated of foraged it must be finely ground.

  • Mortar and pestle for grinding: This must be dedicated to crafts only, never food.

  • Dust mask: These types of clay can be irritating.

  • Small pot: Likewise dedicated to crafting.

  • Mulling slab and muller: For extra finely grinding the finished pigment and mixing paint.

 grinding sepiolite clay

grinding sepiolite clay

Make certain that none of your tools have any water on them, as even a drop will spoil the reaction. After finely grinding, weigh 10 parts clay and 1 part indigo powder. I have used 30 grams sepiolite and 3 grams indigo. Combine these in a small pot and heat over a medium low flame.

Over the course of a few minutes, you will see the two powders combine and turn a uniform blue color. At 356 degrees Fahrenheit the indigo sublimates to a gas, bypassing the liquid phase, and is immediately absorbed by the clay. Remove the pot from heat and allow to cool. The color will have a violet tinge when hot, but turn turquoise as is cools. You now have Maya blue pigment, indigo locked inside and stabilized by the clay.

maya blue recipe
  • A Weighed indigo and sepiolite

  • B Mixed indigo and sepiolite before heating

  • C Mixture after heating: Maya blue!

Maya blue pigment may be stored indefinitely. To use as paint it must be finely ground with a mortar and pestle followed by mulling with a binder to mix the paint of your choice. Check out Kremer Pigments and Kama Pigments course offerings and videos to learn how to prepare your own watercolor, egg tempera, or oil paints.

 mulling maya blue watercolor

mulling maya blue watercolor


bard graduate center residency

Through July 1st I'll be working in the beautiful TAC Makerspace above the Bard Graduate Center Gallery, grinding homemade lake pigments and creating experimental monoprints from them. Stop by to visit during open studio hours 11:30-4:30 Tuesdays and Wednesdays:

TAC Makerspace @ Bard Graduate Center Gallery
18 West 86th Street
New York, NY 10024

This week I'm testing botanically derived pigments on paper, and looking forward to pushing my craft into unknown territory!

stone patterns from lake pigments

indigo as pigment

Straying a bit further afield from the recent posts on alum and the quantity of alum used in paper marbling, let's address the question obliquely raised in the last post on lake pigments:

Indigo is a pigment?

Many of us natural dyers are well familiar with the process of concocting an indigo vat and the working properties of indigo as a dye. It is truly remarkable that so many historical cultures throughout the world developed a practical understanding of the complex chemistry governing the indigo vat, leaving us with a wealth of cultural and artistic heritage centered on this beautiful dye. But indigotin, the indigo blue which colors fibers dyed in the indigo vat, is an insoluble organic compound and can be used as a pigment. It may be mixed with a binder for use as paint without going through the trouble of making an indigo vat. Let's review the process by which indigo is made:

  • Indigo precursors naturally occur in the leaves of an indigo-bearing plant. After harvesting, these precursors are converted by enzymatic hydrolysis to indoxyl.

  • When oxidized, two indoxyl molecules join with oxygen to form indigotin.

  • Indigotin is indigo blue! Indigotin is insoluble, and can be used as a rich navy blue pigment.

  • Natural dyers now mix up their indigo vats to reverse the process. To work as a dye, an antioxidant reduces indigotin to leuco-indigo suspended in water. Fibers lowered into the vat become saturated with leuco-indigo, which spontaneously oxidizes to indigotin when lifted from the vat and exposed to air.

It's quite the feat of organic chemistry, but the peculiar dual nature of indigo provides its distinction as an artists' material. Used as a dye, indigo's working qualities have inspired resist techniques in cultures around the world. After dyeing, the indigo is not chemically bound to fabric and can be abraded from it with much washing and wearing, giving us the particular worn-in look of denim. And because indigo is inert when oxidized, it has better lightfastness that other natural dyes.

grinding indigo pigment
mulling indigo pigment

Sources of indigo pigment

In medieval Europe, indigo was prepared as a pigment by skimming and drying the flower from the surface of a woad vat, called blue florie, or grinding white lead with imported indigo. Indigo was widely available, fairly inexpensive, and in common use as a workaday blue pigment. It is a strongly tinting, dark, and slightly greenish shade of blue. Indigo is certainly a regal dye, one of the few lightfast historical grand teints. But as a pigment, its lightfastness did not match the more permanent and expensive mineral blues.

For use as a pigment today, pure indigo can be finely ground and mixed as watercolor, tempera, or oil paint. If you're a dyer, you can use the botanical indigo powder you already have on hand. You can also purchase the genuine botanical pigment from Kremer,* from Cornellisen in the UK, or you can buy Genuine Indigo paint pre-made by a reputable paint manufacturer.

Synthetic indigo was formulated in the late nineteenth century and is chemically identical to indigotin. Slight color variations between synthetic and botanical indigo are due to additional organic compounds extracted from different species of indigo bearing plants, including the colorant indirubin, which influence the shade of blue. Either botanical or synthetic indigo can be used as a pigment, but not indigo dye sold 'pre-reduced.'

*or get sidelined by Tyrian purple, the other famous vat dye with similar chemistry

 homemade indigo and maya blue watercolors

homemade indigo and maya blue watercolors

What is Maya blue?

Maya blue is an indigo derived pigment used by ancient Mayan and Aztec artisans to color murals and ceramics. This pre-Columbian azure colored pigment is so stable and lightfast it was long thought to have a mineral origin. It is made by heating a finely ground dry mixture of indigotin and clay, either palygorskite, attapulgite, or sepiolite, to 356 degrees Fahrenheit. At this temperature the indigo is sublimated as a gas and replaces water in the clay, becoming a stable compound. Once cooled, Maya blue pigment can be mixed with a binder and used in all sorts of applications. Given that Maya blue requires a small amount of indigo, is lightfast, and is a lovely turquoise shade, it is superior to pure botanical indigo as a pigment.

I have only found Maya blue pigment available from Rublev, but it is not a difficult pigment to make at home. I have small jars of sepiolite clay available in my shop, as it can be difficult to source.

How do indigo and Maya blue fare in paper marbling?

Below are the results of some preliminary marbling experiments with homemade indigo watercolor and Maya blue watercolor.

  • Top: indigo watercolor

  • Middle: Maya blue watercolor

  • Bottom: both shades of blue

  • Column A: no mordant

  • Column B: pre-mordanted with 1.5 teaspoons aluminum sulfate/pint water

marbling tests with indigo pigments

I did struggle with getting the Maya blue to behave, though it functioned well in previous trials alone and mixed with lake pigments. The indigo blue has a beautiful rich hue, and will be useful for mixing dark shades.

As you can see in the right column, the pre-mordanted paper takes a crisper print with less streaking. The question of mordanting for indigo pigments was raised in the wonderful book Marbled Paper: Its History, Techniques, and Patterns:

Why, it may be asked, can some colors (such as indigo) derived from non-metallic materials, seemingly be employed without the use of a mordant? The answer can only be advanced in stages. To begin with, indigo, like the lake colors, which it resembles in several ways, has a low specific gravity. Secondly, it is likely that in its earlier, unsynthesized state, indigo contained minerals and metallic traces. There is good reason to suspect that somewhere during its manufacturing process or final preparation, alum was added, because earths, presumably containing alum and mineral salts, such as chalk, were often added as extenders to cut costs. But, most of all, indigo (like a few other dye-bearing plants) was insoluble in water, and had the ability to fix itself to an organic fiber without the aid of a mordant.
— Richard J. Wolfe

We know that historical paint manufacturers (and maybe some today) stretched or lightened indigo with the addition of various earths, inadvertently making a paint useful for marbling without a mordant. My homemade indigo paint is concocted of pure botanical indigo powder, which apparently does not have enough trace minerals to work quite so well without the help of a mordant.

However, Maya blue is useful for marbling without a mordant due to the chalk in its formulation. It is a lovely (though faint in this test), stable color which European marblers never had access to until the recipe was reverse-engineered in recent years.

Update: After 1 month of exposure to direct sunlight, no fading has been observed in either indigo or Maya blue watercolor samples on unmordanted paper. Lightfastness concerns about indigo pigment can be reserved for very long term light exposure.


alum & lake pigments

In the last post, we discussed the quantity of alum necessary to marble with watercolor and acrylic pigments on paper. There is another class of pigments that can be used for marbling, and was historically an important source of particular hues. These are lake pigments, made from natural dyes. As both a marbler and a natural dyer myself, these pigments are of great interest.

What are lake pigments?

Natural dyes (with the exception of vat dyes including indigo) are water soluble. This means they cannot be used for marbling, as they simply dissolve into the size. In order to make these beautiful organic colors, many of which have no counterpart among mineral colors, useful for  marbling they must be converted into pigments. A lake pigment is made when dissolved dye is precipitated onto an inert substrate - often potash alum. The precipitate is then filtered, washed, and ground. For marbling it can be mixed or mulled with a binder, usually watercolor medium, and used like any other watercolor paint.

If you've ever used the all-in-one dyeing method of mixing mordant, dye, and fiber in one pot, you may have noticed some of the dye spontaneously settling to the bottom. This means the dye and alum have bonded together, making a lake pigment.

mulling watercolor

What role does alum play in lake pigments?

As we learned about alum, it readily bonds to dye molecules, making it a substrate well suited to the formation of lake pigments. Other mineral mordants can function the same way, such as tin and copper salts. Each of these mordant substrates acts to stabilize the dye compound, improving its lightfastness. And just as with natural dyes applied to fabric, the choice of mordant and pH can strongly affect the shade of a lake pigment.

The example below is a lightfastness test of homemade lake pigments( yes, I need to practice patience in grinding pigments). On top is madder lake with copper; below it is weld lake with a little indigo, mixed as watercolors. The left side was exposed to direct southerly sunlight for one month, and the results I think are quite promising. Unfortunately lake pigments suffer from a bad reputation because they are not as permanent as their modern synthetic replacements or mineral pigments. Some lake pigments are certainly fugitive, and care should be taken to keep artwork made with them out of direct sunlight. The most lightfast pigments are made from the most lightfast dyes, such as madder, buckthorn, and weld.

 Lightfastness test of madder lake and weld lake. Left side exposed to sunlight for one month

Lightfastness test of madder lake and weld lake. Left side exposed to sunlight for one month

Marbling with lake pigments

Because lake pigments contain a mordant within them, paper does not need to be pre-mordanted before marbling! I have read this in multiple sources, and the test below confirms it.

  • A: Unmordanted paper

  • B: Paper pre-mordanted with 1.5 teaspoons alum/pint water

The mordanted paper absorbs the marbled print a bit more quickly with a slightly sharper quality, but this shows that pre-mordanted paper is not a requirement.

Lakes are prepared for marbling just like any other watercolor pigment: each color is thinned to a good consistency and mixed with the appropriate amount of surfactant. You don't need to go through the trouble of grinding your own pigments to enjoy working with lakes, any 'genuine' watercolor lake such as rose madder or carmine will work. It can be difficult to know just what manufacturers put in their paints, and whether they are synthetic pigments simply bearing the names of historical shades, so it's worth seeking high quality paints if you want the real thing.

If you are marbling with a mixture of genuine lakes and pigments from other/unknown sources, pre-mordanting the paper is advisable.

testing alum mordant with lake pigments

In addition to lake pigments, I've read that any genuine earth pigment may be used for marbling without a mordant, as earth pigments are composed of minerals. It is clear from natural dyeing that ferrous salts are a very effective mordant, so the iron present in earth pigments should work the same way. I hope to test this in future, and make a comparison of the lightfastness of these samples.

Update: After 1 month of exposure to direct sunlight, no fading has been observed in samples printed on mordanted and unmordanted paper. The alum and chalk present within the lake pigments appears to stabilize the dye colorants admirably.

Please feel free to contact me with any insights or sources for historical pigments!


alum quantity

When preparing paper for marbling, it is pre-mordanted with an alum solution. We discussed the role and varieties of alum in the last post, and let's continue with the question:

How much alum to use?

Marbling instructions vary greatly in the strength of the alum solution recommended to mordant paper. I've seen measurements ranging from 1.5 teaspoons to 5 tablespoons per pint of water. Let's investigate just how much is enough to make a successful print.

What can go wrong?

If too little alum is used, marbled designs made with watercolor or acrylic pigments cannot bond to the paper. Western-style papers used in the European marbling tradition are sized to improve their durability and slow their absorbency. Alum bonded to the surface of mordanted paper is the chemical helping hand essential for linking marbling pigments to the paper fiber, and stabilizing the colors for lightfastness in the long term. Any marbler who has accidentally printed on the unmordanted back side of a sheet is familiar with the disappointment of watching their design wash down the drain with the rinse water, having no alum to hold it fast.

However, if too much alum is used, crystals may build up on the surface of the paper without actually adhering to to the paper fibers. In this case a bit of the excess alum will dissolve into the size as each print is made. If the size becomes polluted with alum, it causes the paint to clump together in a very frustrating way, and must be replaced with fresh size.* If you can feel a buildup of powder on the surface of your paper or see white streaks on colored papers, you are using too much alum.

Additionally, alum is acidic, and using a lot will both waste alum and make the paper overly acidic. Over time, this causes the paper fibers to become brittle and crack apart.

 Watercolor Pigments

Watercolor Pigments

Testing Alum Quantity

These samples, excepting sample A, were coated with a wash of aluminum sulfate dissolved in warm water:

  • A no mordant

  • B 1.5 teaspoons/pint

  • C 1 tablespoon/pint

  • D 2 tablespoons/pint

  • E 3 tablespoons/pint

As can be seen in both the watercolor and acrylic tests, unmordanted sample A is comparatively very pale. This was not a surprise, as it has no mordant at all. I was surprised, however, to find no discernible difference the in strength of the colors in samples  B-E. Any quantity of alum from 1.5t - 3T per pint acts as a successful mordant.

 Acrylic Pigments

Acrylic Pigments

My recommendation: 1.5 teaspoons alum per pint water

I will continue using 1.5t/pint to mordant papers in future, the amount recommended in the first marbling class I took with Stephen Pittelkow. As alum is slightly acidic, I prefer to put as little as needed on my paper to get the job done. Pre-nineteenth century marblers used potash alum, but nowadays you can mordant with either potassium aluminum sulfate or aluminum sulfate - just mix it with warm tap water to ensure the crystals are fully dissolved. Some marblers soak their paper in a mordant bath, some apply the alum solution with a natural sponge or a spray bottle; I use a wide foam brush. As each sheet is coated I flip it over and pencil an X on the back. The whole stack of wet papers is weighted with a heavy board to stay flat. They can be printed in about half an hour when still slightly damp, or kept up to 4 days. I prefer to print papers within one day of mordanting.

If you've prepared your papers with mordant but the marbled design doesn't adhere, you may be using archival paper coated with calcium. Choose a different paper stock and try again.

*Of course, any mistake can become an interesting pattern when repeated intentionally! Mixing a little bit of alum into your gall water or one color of paint can give an intriguing, crunchy texture to a marbled design.