Mason stain raku

Preparing for the Next Raku Workshop: Hump Molds!

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A plaster hump mold for a plate.

I’ll be taking a group of nine (including myself) to another raku ceramics workshop at Dakota Potters Supply this weekend!

This semester has been very busy, so I’ve chosen to focus entirely on hump-mold pottery for this workshop. Using plaster hump molds (convex forms over which slabs are placed and pressed) significantly reduces the time required to make raw ware compared to pinch-pot, hand-built construction.

Hump molds also allow me to easily add and retain complex texture particularly to the interior of a piece; when making a pinch pot, the shape comes from pounding, pulling, and tapping the clay with tools that typically leave a fairly consistent surface. I can add texture to the exterior of a pinch-pot bowl or vase after it is built by rolling it over a texture plate or hitting it with a textured paddle, but I can’t do that to the interior. I can always carve texture into both sides or use other techniques if I really want to, but what I’m getting at is that texture is more complicated to add and retain when working in my preferred pinch pot style.

With these plaster hump molds, I can easily add complex surface texture to a flat slab and control whether it appears on the exterior, interior, or both. I then rely on gentle pressure, gravity, and evaporation to shape the clay, rather than the more aggressive pinch-pot methods that diminish or fully remove surface detail.

I am also continuing to experiment with Mason stains and burnishing on a few of the ceramics!

I saved enough time that I actually made more pottery than I think I’ll have time to finish at the workshop, which is a good problem to have. I’ll nevertheless bring it all just in case I’m wrong about that! Below is all the bisque ware I’m bringing with me. I share space with other folks in our ceramics studio, so I’ve crossed out the pieces in the first photo that aren’t mine. In the second photo, you can see the variety of techniques more closely, and the plate I’m holding corresponds to the hump mold pictured above (as do others).

Mason Stained, Ferric Chloride Saggar Raku Ceramics

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Bisqued pottery ready for the workshop!

Here are the Mason stained, ferric chloride dipped, and saggar fired pottery resulting from my fall workshop! I used three different Mason stains: chartreuse, jade green, and dark teal. I mixed the stains with terra sigillata and applied them in a variety of ways (brush, sponge, scraper). I was purposely going for choppier, sectioned out applications of the Mason stain this workshop to compliment the choppy, random ferric chloride saggar markmaking. (I previously experimented with all-over solid dark teal in varying terra sigillata tints.) To the right is an image of all the bisqued pieces for awaiting ferric chloride dipping for this workshop.

After applying the ferric chloride, I did use a combination of sugar, copper mesh, copper wire, and/or Muehlenbeckia axillaris aka Creeping Wire Vine to contribute additional texture/carbonization, and then wrapped the pieces up in aluminum foil.

First, a large bowl:

Next, a squat vase:

This is a taller, medium-sized bowl:

A sideways-opening orb - I think it’s one of those pieces that doesn’t photograph as well, so it’s significantly cooler in person:

Finally, my favorite piece (mostly due to the finish, but I also like the shape). However, it unfortunately blew off an outer side piece of exterior as well as a piece off the bottom in the stressful firing and cooling process. Since it’s raku anyway (meaning it’s not food-safe or watertight even when undamaged), it’s less important when a piece is damaged. Luckily neither of these blown-off spots went all the way through the ceramic body or caused cracks to the body itself, so they’re just cosmetic and the ceramic itself is still sturdy. I decided to try a kintsugi-inspired repair for the side wall, and just put a foam furniture foot in the bottom cavity for added stability.

If you want to see a clearer detail shot on the kintsugi-inspired repair, here you go! I used a combination of super glue, gold mica powder, a little spackle, and quinacridone / nickel azo gold paint to achieve this repair. I initially had planned on just using super glue and gold powder, but the gold wasn’t showing up as much as I wanted and there was still a bit of unevenness to the edge so I added the spackle and paint to smooth it out and deepen the color.

Again, since the blown-out section was shallow enough, it did not require repair on the interior side.

As you may know, real kintsugi is a much more laborious, toxic process (I did one of the steps in a workshop in Japan in 2024) that when done correctly ensures food-safe results to originally food-safe ware; to my mind it is overkill for non-food-safe rakuware.

Mason Stained, Burnished Obvara Raku Pottery

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At this most recent raku workshop I attended in late October 2025, I experimented with Mason stains in several ways. For the obvara, I did two burnished pieces with very light mason stains. I think it mostly worked well, but the obvara carbonization had a somewhat difficult time really gripping onto the surface, so I think next time I might not burnish and see how that goes.

Here is the first ceramic piece, a burnished oval bowl I did a large polka dot pastel pattern on with small amounts of teal and chartreuse Mason stains mixed into terra sigillata:

Here is the second, a burnished round bowl with a small amount of teal Mason stain mixed into terra sigillata:

My Previous Raku Workshop: Mason Stain Saggar Pottery

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Before we get to my pieces from the October 2025 workshop, I never finished sharing my April 2025 raku pottery as I segued into Japanese residency posts and then went on from there! When we last left off, I had shared my experiments with Mason stains and crackle glazes.

I also experimented with dark teal Mason stain and ferric chloride saggar-fired pottery!

First, we have an orb marked with copper mesh:

This is a small dish which has some marks from a copper wire on the exterior:

Next, an oblong vase! The black smoky spots are from testing out a bit of copper tape:

Finally, a small bowl, using a strip of copper mesh this time!

Mason Stain Crackle Raku Pottery

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The pieces of bisqueware I brought to this workshop (with markings noting which ones broke during the stressful firing process).

At my April 2025 raku workshop at Dakota Potters Supply, I experimented with several new techniques. One that I was really interested in was seeing how adding a Mason stain (in this case, dark teal) to terra sigillata slip and applying it as a top coat on my greenware would ultimately react with different finishing methods.

There aren’t really good recipes for adding Mason stain to wet slip (usually you’d add it to dry clay powder by weight and then add the water afterwards). However, I already had a bucket of mixed up terra sigillata slip in my house, so I just scooped around a cup of it into a small tupperware and added a heaping spoonful of dark teal Mason stain. I then applied it with a fan brush to several pieces of pottery that were still wet - not even leather hard, a bit wetter than that. The coloration significantly lightened as they dried, and I was left with a very light blue coloration. I was worried that might not be enough, so I added another heaping spoonful of the stain to the remaining dyed slip and applied that to a few more ceramics, experimenting as well with placement and markmaking.

To the right, you can see an image of the bisqueware I brought to the raku workshop; the pieces with X’s on them blew up in or shortly after removal from the kilns, so they were thrown out.

At the workshop, I was interested in two different techniques that would make use of the Mason stains: crackle glaze and ferric chloride saggar (or “baked potato”) firing. In this post, I will share the crackle glaze results. I could have used a white crackle glaze (and maybe I should experiment with that to see how opaque it really is), but I was worried it would be fully opaque so instead I applied clear crackle to two of the Mason stain pieces.

This first bowl, which is the rightmost bowl without an X on it in the bisqueware image, just has clear crackle applied to the inside, lip, and just around the lip on the outside. The rest of the piece I left bare to absorb the carbon from the reduction atmosphere.

Unfortunately the crackle either didn’t really crackle, or if it did, the very low contrast between the smoky dark grey and the dark teal is such that very few cracks are really visible. I think if I try this again I will either need to use way less Mason stain or experiment with white crackle or a mix of white and clear crackle. It is still a very pretty bowl, but a bit plainer than I wanted on the interior given the expense and “decorative” status.

Next, I applied crackle glaze to the interior of the taller dish with Mason stain terra sigillata slip on the interior and a burnished exterior. I then applied one coat of naked raku slip resist to the exterior.

The Mason stain crackle interior behaved the same as with the first bowl, so I have similar feelings about it. However, I am enjoying the mixing of techniques on one piece of pottery and plan to explore similar options moving forward.