My goal are to try to reconstruct, using readily available modern materials, the tissue transfer technique for decorating ceramics, and to investigate dry press forming of small wares.
Without yet describing exactly what I am decorating, it must be noted that my wares are not typical of mainstream personal craft. Rather than hand-forming, extrusion, or slip casting, I use a so-called dry pressing (historically identified as "Prosser") technique. In this technique, the ware is formed between shaped dies under pressure, from a powder mixture containing typically around 8% water by weight. For the small pieces that I am making, the ware can be immediately fired either to bisque or to a final state, without waiting for it to dry.
My original objective was cone 10 (2350F) porcelain, but practical considerations of firing time and poor element longevity in my small test kiln, argue for modifying the body composition with frit, to give reasonably good results at 2210F.
A typical body composition starts with 73 parts G-200 feldspar and 27 parts of EPK. On its own, the 73/27 composition when taken to 2350F and held 30 minutes (for my tiny wares), fires slightly off-white and quite translucent. To obtain 2225F firing, I add 6-10 parts Ferro 3124 frit. I mix the dry powders, spray on around 8% water by weight, and transfer the mixture to a mortar and pestle, where I mix until uniform. The result is a powder with some tendency to adhere (though not tenaciously) to the walls of the mortar, and to cohere into small platelike aggregates. When scraped from the mortar, the mixture may be readily scooped as if it were a dry powder.
For test coupons, I form between a stainless steel disk and an acrylic disk, that both fit inside a metal sleeve (bronze shoulder bushing), using an ordinary Harbor Freight hand lever action arbor press. For shaped objects, I use upper and lower die sets transfer-molded from original objects, with the final dies being molded in epoxy resin.
The pressing procedure is simple: situate the lower die inside the sleeve, scoop in some of the powder, pack lightly with the finger or a more loosely fitting flat die, insert the top die, then press. The object is ejected by situating the sleeve over a void (e.g. a stack of washers or a socket wrench of carefully chosen size) and pressing with something sized to push the bottom die out entirely, and the top die out far enough to eject the ware.
The ware typically emerges with a rim of loose powder around the edge, and perhaps with some small bump defects. These can be carefully smoothed off with the smooth skin, callus, or nail of a finger. The ware can be handled carefully, but will usually break if dropped and certainly if subjected to any bending moment.
If this is the final form desired, without decoration, it may be immediately placed in the kiln and fired. My objects are 5/8" to 3/4" in diameter and only 2-6 mm thick, and can thus readily survive rapid heating and cooling.
Dimensional shrinkage through firing typically runs 8-13%.
For image transfer, I bisque fire to 1750F for 25 minutes. The body still is quite fragile to bending, but has a surface condition that seems good for transfer. Some of my forms need holes to be drilled, and drilling works fairly well at this stage.
An alternative body composition uses only feldspar and 3124 frit, with zero kaolin. This composition requires a binder. For reasons related to the historic origin of the process I use casein, extracted from ordinary skim milk with white vinegar, then redissolved in concentrated sodium carbonate (washing soda) solution. The casein + alkali + remaining water (the mixture typically is a very stiff paste after storing under refrigeration) is used at 6-8% by weight, ground in the mortar with the other ingredients, then weighed and re-ground with 8% water added by spray. This composition typically can fire at around 1950F. I mention this more for undecorated bodies; transfer performance without kaolin seems inferior.
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