How to Carve Plaster For Slip Casting Lithophanes Stephanie Osser

Though not often seen in the ceramics vernacular of today, lithophanes were all the rage in the 1820s because of the beauty they created in the dimly-lit homes of the pre-electricity era. I would argue that they need to make a comeback after seeing Stephanie Osser's article in the Ceramics Monthly archive. So I thought I would start my lithophane campaign with today's post.

In this post, Stephanie explains how to create a casting block from which to make a lithophane. Even though our homes are well lit nowadays, we can always use a little more beauty or just a cool nightlight! - Jennifer Poellot Harnetty, editor

PS. To see how to cast a lithophane, see the rest of Stephanie's article in the February 2022 issue of Ceramics Monthly.

Finding Your Materials

To begin, cast a block of plaster that will be carved in relief. Buy the freshest plaster available and be sure to check the date on the bag. A level is your best friend at this step. Use it to make sure your pouring surface and carving blocks and bats are level—this ensures a level surface for making your final slip-cast lithophane.

Cast your plaster carving blocks on top of smooth, shiny granite or marble tile. The plaster will release easily from these impermeable materials and the block’s surfaces will be just as smooth. Build wood frames with clay supports along the perimeter of each tile for pouring in your plaster (A). Start out small, with plaster blocks that are about 5×3½×1 inches. Refine the plaster carving surface with sandpaper once cured (B).

With any leftover plaster, I make thin, lightweight bats (see C), compressing the flowing plaster between two heavy, shiny granite or marble tiles (about 12×12×¼ inch). I make different sizes of these bats, each about ¼  –½ inch thick. Because they are lightweight, I put my wet lithophanes between two thin plaster bats for drying.

When sourcing carving tools, either use what you have, make your own, find dental tools, or buy tools from Kemper, Xiem, or Mudtools (see D). You will definitely need a fettling knife and a rubber-tipped, two-sided smoothing tool that can be trimmed to the shape you need. This is helpful in scoring and slipping out-of-reach areas like the bottom of a cup—should you decide to add a lithophane there. My favorite tool is a tiny metal rib made at Kecskemét by their wonderful support technicians. See the rib pictured in the bottom right of image D. If you’d like to make one of your own, trace it and cut the shape from metal or a plastic card. 

Mix the plaster and carefully pour it into your frame on the marble slabs. Once set up, smooth the uneven edges on the top and bottom. Keep them wet: they are easier to carve and there will be no plaster dust. 

Make a damp box out of a plastic container. Pour about a 1½-inch layer of plaster into the bottom, let it set, then keep it moist with a tight-fitting lid. This damp box helps keep the lithophane blocks wet as I carve, and I also use it for storing my slip-cast pieces of cut-out lithophanes to add to the bottom or sides of vessels. Everything stays damp and ready for when you resume work. Remember to spray water on the plaster in your damp box while in production. 

You may use both sides of the damp plaster block to carve separate images. Starting with my pencil guidelines on the plaster, I carve an outline of my image on the plaster. Keep in mind that this is going to be a very shallow bas relief with no undercuts for easy release and with three levels: foreground, middle ground, and background. I use a curved clean-up tool and start with the shallow areas of the image, then carve the deeper areas (E). The lowest depth should be about 3mm (⅛  inch). With experience, you can guess what depth is going to produce various tonalities. The shallowest areas will be the brightest, with half tones created by various thicknesses of the fired porcelain.

You can press some soft porcelain clay or a white clay body (to keep your plaster clean) onto your image to evaluate your results so far. This process can also clean up some of the carved plaster. When you are done and have a clean final product, you can even make some bisque stamps by pressing clay into areas of the carving. 

Use fine-grit sandpapers or sanding sponges for smoothing and burnishing both the carved surfaces and areas around the carved imagery while the plaster is still wet, and wash your carved plaster block to remove all remnants of plaster debris. Let the plaster relief block dry completely.

**First published in 2022.