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2019 Jiggering-Casting Project of Medalta 66 Mug
A cereal bowl jigger mold made using 3D printing
Beer Bottle Master Mold via 3D Printing
Better Porosity Clay for Brown Sugar Savers
Build a kiln monitoring device
Coffee Mug Slip Casting Mold via 3D Printing
Comparing the Melt Fluidity of 16 Frits
Cookie Cutting clay with 3D printed cutters
Evaluating a clay's suitability for use in pottery
Make a mold for 4-gallon stackable calciners
Make Your Own Pyrometric Cones
Making a high quality ceramic tile
Making a Plaster Table
Making Bricks
Making our own kilns posts using a hand extruder
Making your own sieve shaker for slurries

Medalta Jug Master Mold Development
Mold Natches
Mother Nature's Porcelain - Plainsman 3B
Nursery plant pot mold via 3D printing
Pie-Crust Mug-Making Method
Plainsman 3D, Mother Nature's Porcelain/Stoneware
Project to Document a Shimpo Jiggering Attachment
Roll, Cut, Pull, Attach Handle-making Method
Slurry Mixing and Dewatering Your Own Clay Body
Testing a New Load of EP Kaolin
Using milk as a glaze

Medalta Ball Pitcher Slip Casting Mold via 3D Printing

This project will follow progress as I create a master mold for use at Medalta Potteries in Medicine Hat. For information on the general track I will take check the beer bottle and mug mold project (linked below). Various aspects of this shape are quite challenging (e.g the handle, the shape of the lip, the angled foot). I will post pictures as I repeat cycles, version numbering where appropriate. When it is all working well I will remove all but the last successful version.

Related Information

Medalta Ball Pitcher

Here is an example of one that was for sale on Ebay. The inset bottom will be a challenge, for version 1 we will likely settle for a flat bottom.

Initial mockup for 1940s Medalta Potteries ball pitcher

Medalta ball pitcher 3D drawing

No molds have survived so we are going to start from scratch, making the smallest of the sizes first. We will use Fusion 360 and 3D prints in PLA to create a block mold to make a rubber case mold. Drawing this correctly should reward me with some new 3D drawing skills. The geometry of the lip will be challenging. Likely the piece will need to be cast with a flat top (filling and draining done through the pour hole). I will likely have to create a 3D-printed PLA template as a cutting guide to get the contour of the lip right.

Determining the basic geometry of the ball pitcher

From a side-shot, I was able to boil it down to this basic shape and size. It seems clear that the mold needs to be made to cast it upright (for easiest drain).

Medalta ball pitcher first 3D print of block mold

I cut it in two horizontally in the slicer software printing the top part upside down. This minimizes the amount of support that needs to be printed (thus greatly reducing print time). This was done on my Prusa MK4, the two halves mate perfectly. These two took about 6 hours to print. The support easily releases (I use a needle nose pliers).

Printed mold halves taped, railed, ready to fill

Filling the printed form, from the back, with plaster makes it rigid for the next step, pouring a case mold. I have removed the support so plaster fills all recesses. The flimsiness of the printed shell is actually an advantage, the weight of the plaster pushes the mating surfaces down onto the table. The rails impose perfectly square corners and flat sides. I will pour the plaster just to the top of the printed part (not the top of the rails).

The plaster-filled block mold negatve

The two parts mate perfectly, the slight seam is easy to remove from the plaster negative that will be poured against this. Although polygons are visible on the inner side, they will not show on glazed pieces. Notice there is no provision for matches or spare, the reason will be clear later in the process.

Ready to pour a block mold

I have sanded the rings on the inside top and bottom - just smooth enough the release won't be too difficult (on the plaster block mold and will be able to smooth them more effectively). I also applied some Murphys Oil Soap on the those sections. Now it is just a matter of filling this with plaster.

Two block molds are ready for casting working molds

At this stage any imperfections in the 3D print are easily removed from the plaster surface.

Block molds railed ready to pour working molds

Medalta ball pitcher block molds

The plaster block molds have been oiled using Murphys Oil Soap. I printed the side rails to fit (by measuring the lengths and widths precisely and dividing them by two).1.7kg of plaster was enough to fill them both.

First working mold ready for pouring

Two halves of my first test working mold are ready. I'll put them in our lab dehyrator for 6 hours at 150F to dry them out over night. I'll cast the first pieces tomorrow using our new recipe for M370 Casting.

First ball pitcher casts successful. Sort of.

The top has not yet been trimmed. We first tried casting this using a fast-casting clay body, but the process was very quick and the pitcher dried so fast that by the time I got it out of the mold it was too brittle to cut properly with a fettling knife. This is a second cast, using M370C. It casts about three times slower (3-hour mold cycle time) but there are no issues with cutting the top to shape. Well, actually there are - it is very difficult to get the shape right, a template is needed There is an issue with the handle also - it is too close to the body and too thin and delicate.

Version 4 Ball Pitcher 3D printed block mold

3D-printing v4 of Medalta ball pitcher mold

This project continues to demonstrate that multiple redesign, test cycles are a fact of life when making a new shape. 3D printing makes this so much easier. Here are the changes from v3:
-This time I am not going to back fill with plaster. I have heftier side rails that should hold things firmly in place.
-The rim is now cast in into final shape.
-The includes a distinct footring, this will enable easier cleanup of glaze on the foot and a cleaner edge line.
-The handle is thicker and looks a little further from the body (to enable getting my fingers in there).
-I am using natches this time, the two 9mm holes will mount embeds (the retainer and embed are shown beside the holes) - they will position flush in the case mold (I will propagate the embeds into the working mold also).
-I am casting it upside down, positioning the spout between the lower handle join and the foot ring. We will drain for ten seconds then plug the hole using a plaster insert made to fit snug. Remaining slip inside will refill the hole and even build the wall a little thicker there (increasing wall strength by the lower handle join).

Ball pitcher v.4 case molds cast

3D printed PLA mold to plaster case mold

We are just using pottery plaster for now. Notice the embeds for the natches. This time I did not backfill the 3D prints, that is better - because they are flexible they were much easier to remove from the set plaster. The side rails help keep them firmly in place and scotch tape on the backs was sufficient to keep them lined up at the join (these prints have a wall thickness of only 0.8mm). I did not need to use a parting agent nor did I do any smoothing on the 3D prints (although some cleanup on the plaster case mold will be done). Next step: A working mold, version 4.

Ball pitcher v.4 working test mold cast

The natches are working perfectly, the two halves mate perfectly aligned. You can see the plug that will be inserted after pre-draining (and the pour spout). This will be suitable for testing but I will have to go to version 5 because this was too difficult to extract from the block mold (because of verticals on both the top and bottom of the pitcher, this will have to be rounded).

Inbound Photo Links

MK4 3D printer for ceramics
The Prusa MK4 3D printer is worth the upgrade from MK3


Medalta in the historic clay district site
Medalta, Hycroft and Sunburst Pottery Catalogs from the early and middle 1900s
Medalta Collections Database at PastPerfect - Search for the word "drawing" to see the mechanical drawings for hundreds of pieces
Projects Beer Bottle Master Mold via 3D Printing
A project that took several years of failures and blind allies and is finally coming together - so much simpler than expected!
Projects Coffee Mug Slip Casting Mold via 3D Printing
A potter can now use AI, 3D CAD, 3D printing and custom clay bodies to slip-cast beautiful quality stoneware pottery mugs. It is efficient and practical.
Projects Nursery plant pot mold via 3D printing
Glossary Slip Casting
A method of forming ceramics. A deflocculated (low water content) slurry is poured into absorbent plaster molds. As it sits in the mold, usually 10+ minutes, a layer builds against the mold walls. When thick enough the mold is drained.
Glossary 3D Design
3D Design software has revolutionized traditional ceramic manufacturing, now it is accessible to hobbyists and potters.
Typecodes Mold making using 3D printing
An ordinary consumer 3D printer has many exciting possibilities for making many types of molds, it is a place where people having both artistic and mechanical abilities can get a double the dopamine!
By Tony Hansen
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