Sizing for paper

I received a copy of Rudolf Hainbach's Pottery Decorating, 2nd English edition, 1924.  Various works have disparate descriptions of the soap sizing and its application to the tissue.  The sizing is typically referred to as a solution or a thin solution of soap in water.  One source specifically says potash soap.

Hainbach gives more detail: "... the color does not come into direct contact with the paper, but rests on the layer of soap."

"The soap mass for this purpose is prepared by cutting good white curd soap into fine shreds, and boiling these with pure water in a vessel until fully dissolved, so as to form an opalescent but transparent liquid that is viscid when warm, and in this condition will flow from the spatula."

He also says that after transfer, the ware is put into water  at 30-40°C, swelling the paper and dissolving the soap layer, "... destroying the connection between the paper and the color."

This argues for a contiguous and not too thin layer of soap.  I prepared some soap solution, more concentrated than described above, and squeegeed it onto several types of tissue.  I will try printing some of these tomorrow, also using a modified ink.  This ink contains some gum dammar, that being the most readily available natural resin (the art store has it with encaustic paints).  This seems to add tack.  I am eager to try it after the tissues dry.

The soap that I am using is a locally made unscented vegetable oil bar soap.  Soaps of the original time almost certainly were made from animal fats.  My grandmother made an eye stinging but very effective soap from saved bacon grease and lye.

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I was able to try printing with the soap sizing mentioned above.  Ink take-up on the paper seemed reasonably good, but the fired image was too faint.  Most likely I needed more oxide proportion relative to frit.

The ink formulation that I was testing here also contained gum dammar, which I had hoped might act as a tackifier.  The jury is out on that.  Some Burgundy pitch (typically a spruce resin product, sold for optical polishing) arrived today, and I will be trying that as well.  The gum dammar seemed to make the ink more fluid when heated, but a bit tackier when cool than with burnt plate oil alone.

The heavier soap sizing, and the use of warm water per Hainbach, gave promising results with respect to water lift-off of the tissue from the ware.  Both sewing pattern tissue and cicada wing xuan paper floated free with just a bit of agitation, and no pulling required except to get the paper out of the way and keep it from settling back down onto the ware.  Sewing pattern tissue seemed to give the better transfer, but cicada wing floated away more readily.

Promising new paper

A correspondent on a ceramics discussion site recommended "cicada wing" xuan (shuen) paper as used for traditional Chinese brush painting.  Blue Heron Arts sent some amazingly quickly.

It has poor wet strength but perhaps adequate.  It is said to be sized, maybe with glue and alum.  It has some of what appear to tiny shiny mica flakes, but these are sparse and appear not to cause trouble.

Before making the impression, I size one side of the paper by rubbing bar soap on it, then mist the other side very lightly with water, then print on the soaped side.  The soap seems to make the paper more supple even before misting.  Ink take up seems very good, and unlike tissues, the ink does not push much through voids to the back side and backing sheet (dampened newsprint).

Unlike sewing pattern paper, it tends to disintegrate rather than float off intact when soaked after transfer.  This is a bit annoying, but it might not be a big problem.