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:
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.
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.
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.
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.
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.