alum quantity for fabric marbling

In recent posts I’ve looked into the types of alum and the quantity necessary for marbling paper; now let’s turn to fabric marbling. There are a lot of different recipes for mordanting fabric prior to marbling, but with my natural dyeing experience to guide me, I’d like to share my method.

alum quantity for fabric marbling

Remember that alum is the compound most commonly used to mordant both fabric and paper. It bonds readily and permanently to other molecules, creating a link between fiber and marbling pigment. Our aim in mordanting is to evenly apply an alum solution to our fabric before marbling, just enough for a permanent print.

Fiber preparation

Firstly, choose an absorbent natural fiber or blend for your fabric. Thoroughly wash the fabric to remove any starch, sizing, or dirt from its surface - these will impede both the mordant and marbling from being absorbed.

Mordanting by weight

Using a metric baker’s scale, weigh your dry fabric (this can be done before washing).

  • For plant fibers (cotton, linen, bamboo, ramie, hemp) or fiber blends, measure alum equal to 15% of the weight of your dry fabric.

  • For animal fibers (silk), measure alum equal to 8% of the weight of your dry fabric.

Fill a clean container with enough warm water for your fabric to swim freely. This can be a bucket, plastic storage container, or your bathtub. Add the alum to the water, stirring until it is completely dissolved. Lower your fabric into the alum solution, swishing it around to release air bubbles. Leave the fabric to soak for 40-60 minutes, stirring every 15 minutes for even absorption.

Empty your mordanting container and fill with fresh water. Rinse your fabric 1-2 times by wafting it through the water to remove excess alum.

Hang the fabric to dry. Mordanted fabric may be stored for up to 6 months before use. Iron with steam before marbling.

Mordanting by volume

If you don’t have a baker’s scale, you may choose to mordant by volume instead of weight. It’s not quite as scientific for large amounts of fabric, but it works well for small projects.

Find a container large enough for your fabric to be fully submerged and swim freely when it is unfurled. Fill this with warm water, measuring as you go. For every quart of water, add 1 1/2 teaspoons of alum (that’s 2 tablespoons/gallon). Stir until the alum is completely dissolved, then lower your fabric into the alum solution. Swish it around to release air bubbles and leave the fabric to soak for 20 minutes.

Empty your mordanting container and fill with fresh water. Rinse your fabric 1-2 times by wafting it through the water to remove excess alum that is not bonded to the fabric.

Hang the fabric to dry. Mordanted fabric may be stored for up to 6 months before use. Iron with steam before marbling.

The dangers of poor mordanting

I’ve seen recipes calling for as much as 1 1/4 cups alum (20 tablespoons) per gallon of water. That’s a lot. The problem with mixing a very strong mordant solution by following a heavy-handed recipe or failing to follow any recipe whatsoever may not be immediately evident. But some problems might arise:

  • Alum is slightly acidic. You can over-mordant your fabric by mixing a very strong alum solution or leaving the fabric to soak too long. Over time, that acidity causes the fibers to become brittle and break apart. If your marbled fabrics feel very dry or brittle, or if they tear during washing or sewing, they are likely over-mordanted.

  • I’ve read that alum ‘eats’ or ‘decomposes’ fabric, and it should never be mordanted more than a few days prior to marbling. This is true only if you over-mordant and thus leave your fabric in an acidic state. Following a decent recipe will allow you to mordant fabric months in advance of marbling with no detriment.

  • Failing to rinse your fabric after mordanting can leave it with excess alum sitting on the surface that is not bonded to the fibers. If the un-rinsed fabric dries with any wrinkles, that alum can pool in the creases and give you a streaky print.

  • Fabrics that have not been rinsed can deposit excess alum into the size, degrading it over the course of multiple prints. Or worse, your print may bond to the layer of alum sitting on the surface of the fabric, then flake off during rinsing.

Unfortunately fabric that is over-mordanted cannot be saved; alum forms permanent bonds and cannot be removed. If you have a batch of fabric exhibiting any of the issues above, best scrap it and start fresh. Small amounts of mordanted natural fiber fabrics (not yet printed) can be torn into thin strips and added to the compost.


Further Reading

fabric marbling with watercolors

I’ve been marbling fabric with acrylic paints for several years, but must ask the question: Is it possible to marble fabric with watercolor paints? This question has arisen for a few reasons:

  • Historically, all water-based marbling was accomplished with watercolor or gouache paints formulated from natural pigments and binders. The colors of the historical, natural palette are subtle but pleasing.

  • Examples do exist of cloth marbled with watercolor paints, notably the cover of Charles Woolnaugh’s 1853 book The Art of Marbling. Hand marbled book cloth was produced beginning in the 1830s as a durable, inexpensive alternative to leather.

  • In search of the most ecologically sustainable practice, nontoxic naturally-derived watercolor paints are a great option. Together with carrageenan size, natural ox gall, and natural fiber fabrics they make a biodegradable toolkit.

  • Watercolor paints have a noticeably longer drying time and do not posses some of the quirks that give acrylics a different visual and working character.

Acrylic paints, made from synthetic pigments and a polymer binder, were first developed in the mid-20th century. They are water soluble when wet, but dry to a water-resistant plastic film. Most contemporary literature recommends acrylic paints such as Golden Fluid acrylics, Jacquard Dye-Na-Flow, Jacquard Marbling Colors, or Boku Undo inks (made with a PVA binder) for marbling fabric. The fabric must be pre-mordanted, and some sources recommend heat setting or curing the fabric after marbling to increase washfastness. Some marblers also add a binder designed for applications on fabric, such as Golden GAC 900, which requires heat setting. The color saturation, water-resistance, and flexibility of acrylic paints makes them a great option for fabric marbling. However, acrylics leave a slightly plastic hand on delicate fabrics, and they are not the most environmentally friendly choice.

watercolor marbling

We know that watercolor paints can be used to marble fabric, but how do they compare to acrylics? Marbled fabric was historically used primarily for book cloth, which requires durability but not washfastness. Continuing my informal marbling experiments, I tested both watercolor and acrylic paints on fabric for washfastness.

Process

Mordanted silk and cotton samples were marbled with watercolor and acrylic paints. One swatch was held back as a control, and a second swatch was run through the washing machine and dryer on a normal setting twice. I would usually hand wash or launder marbled fabric on delicate, and always line dry! But for the sake of this experiment, I chose to accelerate the wear and tear marbled fabrics are exposed to over repeated washings.

marbled silk samples

marbled silk samples

  • 1A Watercolor paint on silk

  • 1B Watercolor paint on silk after washing

  • 2A Acrylic paint on silk

  • 2B Acrylic paint on silk after washing

The watercolor paints printed beautifully. The slightly less saturated palette is due to my choice of historical pigments. But it is clearly evident that watercolor paints are not durable enough to withstand laundering. While the acrylic sample 2B has suffered somewhat in washing, watercolor sample 1B is much the worse for wear.

marbled cotton samples

marbled cotton samples

  • 3A Watercolor paint on cotton

  • 3B Watercolor paint on cotton after washing

  • 4A Acrylic paint on cotton

  • 4B Acrylic paint on cotton after washing

If anything, the results on cotton are more extreme. While the laundered acrylic sample 4B has faded only slightly, watercolor sample 3B has nearly vanished.

A note on heat setting

In natural dyeing, we often heat set dyed fabrics to catalyze bonding between the dye colorants and mordant. I had hoped that heat setting watercolor marbled fabric might likewise facilitate permanent bonding to the mordanted cloth. However, watercolor swatches heat set by ironing showed no discernible increase in washfastness in this experiment.

My recommendation

Watercolor marbling is perfectly adequate for fabrics that do not require laundering. Choose an absorbent fabric, then scour, mordant, rinse, dry, and iron it prior to marbling. Heat setting or curing the print is not necessary for fabric that will not be washed or subject to much abrasion (but it certainly doesn’t hurt).

Based on this experiment, watercolor marbling is not recommended for fabrics that need even infrequent washing.

Acrylic paints are the best choice currently available for water-based washfast marbling on fabric. To make your prints as durable as possible, choose an absorbent fabric, then scour, mordant, rinse, dry, and iron it prior to marbling. After marbling, very gently rinse the print to remove excess pigment and size. Hang to dry thoroughly. Iron to heat set acrylic paints following the manufacturer’s instructions, or allow to cure for 1-2 weeks. You may now choose to wash the printed fabric with a fabric softener to give it a soft hand.

Always wash marbled fabrics by hand or treat as delicate, and line dry. Even the most permanent marbled prints are subject to fading if washed often or treated roughly, as the fibers supporting the print are gradually broken down.

As always, please be in touch to share your marbling experience, recommendations, and resources!

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.