In late May I found out that I needed to make five dozen custom tiki cups for an event in mid-July. I've never made a tiki cup before, although I'd thought about it, so I wasn't at all set up to create any, let alone more than 50 in about seven weeks. Potters will understand, that's a very short timeline for someone who only does pottery part-time, especially considering firing schedules.

This meant that a lot of more standard methods of making them weren't a possibility. Creating new plaster molds for casting would take too long, especially since I don't regularly do casting and am not set up for it. Sculpting the cups individually would take even longer. What could I do to put designs on them that would be relatively fast, both to engineer and to make each cup?

I asked on a ceramics forum (Clay Buddies) for ideas, and several people (including Tim See) suggested that stamps were my best bet. I hadn't had a lot of luck, though, stamping individual cups will on (or off) the wheel. So after some tinkering, I tried a different approach that I'd used with other textures; instead of bringing the stamp to the cup, I'd bring the cup to the stamp. I needed a texture mat.

TPU is flexible printable plastic. I've been finding it works much better for stamps than rigid plastic, both because you can bend it around pieces and also because it sticks a bit less. It's perfect for texture mats. So I found some cartoons of tiki faces on a clipart site, modified them to make them simpler and more geometric, and turned one into a texture mat, which I printed in black TPU.

The next step was to create a wooden form for the inside of each cup, which could be used to roll the cup across the texture mat without losing its shape. I made mine from a 2" diameter post and inserted part of a broom handle for control. I did not want to 3d print the inside-cup dowel, both because plastic sticks to wet clay, and because I was concerned about strength.

Next, I had to throw a bunch of perfectly cylindrical cups, with interiors that were 2.25" diameter and 5.5" tall to match the dowel. This was a bit harder than it sounds; I hadn't thought about the fact that my hands are too large for a 2.25" diameter cup, and as a result I had to finish each cup using a throwing stick on the inside.

The next step was to roll the cups on the mats to make the tiki faces. The first batch of 6 cups I ended up turning into regular mugs, because I found out (the "hard" way) that the clay needed to be quite soft to take an impression, like just 12-15 hours after throwing.

I learned a few things with this first trial. First, it was quite difficult to get a good impression if the design, like this one, had any large blocky shapes. Also those squares at the top with sharp corners really dug into the clay, ruining some cups. But I felt like I was on the right track.

So I did two new designs, which were composed only of lines, and gave fairly even design coverage over the whole height of the cup. I also started dusting the designs with dry clay to make them stick less.

This worked a lot better. Those designs really popped and were clear all over the cup, and would look good once glazed.

Next I repeated that several dozen times. And then drying, and firing, and glazing. Tip: if you do use dry clay to prevent a stamp from sticking, make sure you brush off all the loose dry clay once the piece hardens. I didn't do that on all the cups and it ruined the glaze on a few.

I glazed them all using translucent glazes (two celedons and two others) which would do the best job of emphasizing the tiki designs. They were all done, not just on time for the event, but actually two weeks early. Yay!

I'll definitely use this technique again, although I'll make some changes. Some padding on the dowel would probably be good. Also, maybe a cup form that was a bit wider and shorter to speed up throwing. But it worked pretty well.

Lots of potters by now are familiar with the Ball Opener tool, popularized by Tom Whitaker. Speedball even has a version for sale, although I'd argue that it's inferior to one you make yourself from PVC. I use ball openers when I make matched sets, because making sure that the bottoms of all pieces are identical thickness makes it much easier to make them all identical.

After a few years of making plain glued PVC ball openers, I started thinking about how I could improve the device. Particularly, how could I incorporate 3D printed elements to make it better, and maybe make the thickness dynamically adjustable? I did a bunch of experimentation, and a bunch of trials, and have come up with a new design that I call "Ball Opener Mark 2". For any of you with a 3D printer and assembly skills, I think you'll find it a worthwhile improvement over the individual design.

Building The Mark 2

To make the Ball Opener Mark 2, you will need:

• 2-3ft of 1/2" thick wall PVC pipe
• A 4-way PVC junction and two elbows
• 3ft of 1/2" wooden dowel rod
• A cutoff, table, or band saw for cutting that pipe and dowel
• A power drill and 1/8" bit
• One 2.5" piece of 3mm brass rod
• PVC "glue"
• Superglue gel or E6000 glue
• All of the 3D printed elements included in this set
• A toothpick

First, you'll want to print all the 3D printed items for the Ball Opener. There's a bunch of them, so get started now. PLA filament is fine. See the notes in the Thingiverse entry on how to print them.

Cut the PVC pipe into two pieces 4.5" long, two pieces 3.5" long, and one piece 3" long. Fit the two 3.5" pieces on opposite sides of the 4-way junction, and cement them in with PVC glue. Fit the elbows onto the ends of those pieces, and glue them in, making sure that they are exactly parallel to one of the unused openings of the 4-way junction. Fit the two 4.5" pieces into the elbows and glue. Finally, glue the 3" piece in the 4-way opening on the same side as the other two pieces, forming an "M" out of PVC. Allow all the PVC glue to set, around 1 hour.

While the PVC glue is setting, cut three 6" pieces from the dowel rod. Attach each of the 3D printed ball opener Opener Tips to one of the dowel rods. Glue these in with the superglue/E6000. Bend down one end of the brass rod, about 1/2".

Once the PVC glue has set, glue in the rest of the 3D printed parts. The two PVC Plugs go on the two outer legs of the M; these are to keep the PVC from getting worn down by the friction of the wheel too fast. The Top Plug goes in the top of the 4-way junction. As you glue this in, make sure that the slot on top is exactly parallel with the PVC cross pieces. Now, time to wait for all that glue to dry, at least a couple hours.

Once that's all set, fit each dowel into place by inserting it up through the center of the M. Mark the dowel rod where the slot in the Top Plug is. Take it back out and drill a hole through it at that mark. Repeat with the two other dowels. Label each dowel with its gauge thickness with a sharpie.

Your Mark 2 is now manufactured. You might want to wait overnight for all glue to be completely set.

Using the Mark 2

To use your new tool, push one of the Opener Tips with its dowel through the center of the M, and then anchor it using the brass rod. You can change the height by switching which of the Opener Tips you use, and you can (and should) 3D print more with different thicknesses. I have named the Opener Tips with the distance from the wheelhead, which becomes the thickness of the clay bottom. These distances are not exact, particularly given that none of us is precision-cutting our PVC.

Now, you can use it like a regular ball-opener per Tom's video.

However, the Mark 2 comes with a bonus feature: a Width Gauge. I designed this because, in order to make matching pieces, I also wanted to make sure to open each hole the exact same amount. The way you use it is this: before locking in the dowel with the brass rod, you slide the Width Gauge over the top of the 4-Way, ringing the Top End, with the slots matching up. Then lock everything in place with the brass rod. Put a toothpick in the little hole, pointing down. When you throw, follow the toothpick with your eye to see if you've opened the hole the right amount.

The example width gauge in my 3D print set is for a hole 95mm wide. You will, of course, want to make ones a variety of sizes. Note that the flat bar needs to be 27mm shorter than the desired hole width, because of the width of the ball opener itself. Eventually I'll create an OpenSCAD template for generating them.

On to the Next

I hope you enjoy building and customizing your own Mark 2 Ball Opener.

For me: it's been a learning experience, and I already know how I want to build the Mark 3.

Q&A

Why use PVC plus 3D prints instead of 3D printing the whole thing?

Extruded filament plastic, regardless of filament type, doesn't have anywhere near the strength of commercially formed PVC pipe. A fully 3D printed model would break in use. Another artist is experimenting with resin printing, and I'll update this based on what they find out.

Why not just make a bunch of all-PVC standard ball openers at different heights?

Because that would have been a lot less fun, and take up more space. Also, this design has some other advantages like the width gauge.

Is it important that all my pipe and wood cuts are exactly perpendicular and smooth?

Yes.

Why do you mix American and metric measurements?

Sorry, I live in the USA, that's how things are here. If you're in another country and want to make an all-metric one, you'll need to redo the measurements yourself.

I'm doing a large order of plates for a customer, which need to match and stack properly (they even have to stack with plates made by another potter, but that's a complication I'll leave out of this article). One problem making porcelain plates is that you have to throw on a bat, and both plastic and wood bats work poorly, often causing the plate to dry unevenly and crack despite your best efforts. Plaster bats, however, absorb water from your piece, allowing you to dry it in place and have it separate naturally from the bat with relatively even drying.

Now, you can buy plaster bats from several sources, Hydrobat being the most popular in the US. This is a great option if you only need one or two, but if you really need a dozen (or more) then they get expensive very quickly. Since I need to make 80 plates, I need at least 10 bats so that I can have that many drying at once. Using premade plaster bats also makes adding a foot grove impractical. This means casting my own plaster bats.

Wait, you ask. Foot groove? Yes. By carving a round groove into the plaster bat, you can "instantly" have a foot for your thrown plates. As well as ensuring consistent foot diameter, this has the advantage of eliminating a lot of clay waste; trimming a foot on a plate often means trimming off up to 25% of the clay you threw it with.

Before you start, casting bats takes considerable space, and works better in a warm, dry environment. I recommend waiting until summer to make a bunch of bats so that you can do most of the production process outside.

Here's everything you'll need for your bat making:

• bat mold(s) (including bat pin molds)
• plaster
• a good water source
• scale accurate to 5g/1oz
• mold soap and a sponge
• a spirit level (or similar tool)
• a flexible bucket for mixing
• a drill with a mixing blade or a very big whisk
• a food-service-sized spatula or other long-handled scraper
• small plastic paint scraper
• pottery trimming tools
• t-square or similar

Now, you can make a bat mold from any round, smooth-bottomed object of an appropriate diameter. For example, you could cut off the bottom of a 5-gallon plastic bucket. Shapes that taper slightly are better because plaster expands while setting. That's the easy part; the hard part is that you may want to cast indents for your bat pins in this shape, and designing a bar that will let you place them exactly centered. I can't show you that, though, because I chose to buy a mold system from Pure And Simple Pottery Molds instead. I did this because I didn't have time to mess around with perfecting a mold, and the "keying" system for mounting bats using the P&S molds makes it easy to take them on and off the wheel, even multiple times per piece. The drawback of using the P&S system (besides the cost) was that it reduced me to casting one bat at a time.

Now, let's talk plaster. If you're in North America, USG Pottery Plaster #1 is the standard pottery casting plaster, if you can get it. Since the USG plaster mines have had issues lately, you can settle for USG Casting Plaster #1 and it should work fine. For extra hard and durable bats, you can use Hydrocal, whose texture is somewhere between plaster and concrete. Do not use Hydrostone, as it does not absorb water well. Potters in other parts of the world will need to find their own equivalents.

While you're special ordering materials, you'll also want mold soap. This is a thick soap you use to coat the insides of the mold to make sure that the plaster does not adhere. While you can use dish soap, vegetable oil, or other household substitutes, mold soap is formulated to give you a thin but effective coating on the mold, preventing the pottery from sticking without leaving patterns on the plaster from bubbles and streaks. I use Georgie's Mold Soap, which seems to be the same formula as Laguna Pure Lube.

Assemble all your tools and materials in easy reach. Once you start mixing the plaster, you will have minutes to follow the rest of the process and you don't want to be hunting for things.

Now, prep your mold. First, use the spirit level, plus shims, wedges, and boards to get the bottom part of the mold completely level. You don't want your bat to be thicker on one side than the other. Using a sponge, gently coat the bottom part of the mold including the edges in mold soap. You're looking for a thin but uniform coating, like thin paint, no more than 0.1mm. You also need to soap the top insert of the mold, which is the keying piece for the P&S mold, or your home-designed mold.

For the P&S mold, you have to add bat pin holes, because even though the bat won't lock onto the pins, it needs to clear them. I bought two socket cap screws that were one size larger than my bat pins, with matching wing nuts. These also gave me convenient handles for the top piece of the mold. P&S instructs you to bolt together the insert and the wheel head mount when casting, and I have no idea why, because that didn't work at all for me.

Now, you're going to mix your plaster. For a 12" P&S bat you'll mixing 6lbs of plaster with 4lbs of water. If your tap water is very hard or otherwise chemically notable you'll need to use bottled water; in Portland, I'm able to use tap water. You also want to use a bucket that will allow you to easily clean all of the waste plaster out of it, because you don't want new batches touching old, hardened waste plaster (it messes up the hardening process). On a suggestion on Clay Buddies, I bought a flexible feed bucket from our nearest farm supply store, and greased it with a little bit of mold soap just to make sure.

Mixing plaster into water uses an odd process called "slaking". You pour the water into the bucket, and then scoop in the plaster, shaking it to distribute it. If you've done this correctly, it should just start to mound up and break the water level as you run out of plaster. Leave it to sit for 2 minutes or so, and then mix it. I use a drill with a glaze-mixing blade to mix my plaster, but you can also use a large whisk and spatula if you want to put some muscle into it. Mix for roughly 1 minute, making sure to hit the "corners" of the bucket, and not to break the water surface a lot with your blade or whisk because you do not want to incorporate a lot of air. Once mixed, let it sit for 2-3 minutes; the plaster should thicken to the consistency of buttermilk, at which point you want to pour immediately.

A note about timings: the amount of time that plaster takes to set is very dependent on the temperature, both air and water. The timings I'm giving here assume that it's 75-80F while you work, and that you're using cold tap water. If it's 95F and your water is warm, you will need to move faster. Likewise, the plaster will take much longer to set in the middle of winter.

Pour the plaster into the mold. For the P&S mold, you want it to come up to about 2mm below the edge of the mold basin. Then slide in the insert; if it's the right amount full, a little plaster should bubble out of the holes you've left open, but not a lot. Tap the top part of the mold for a minute or so, to encourage any air bubbles to migrate out.

Let it set for 25-40 minutes, depending on ambient temperature. Pry the top part of the mold off using the plastic paint scraper. Flex the mold around the plaster, and then flip it upside down to harden/cool. It will need at least 24 hours of rest time before it's ready, but days is better, to make sure it's as dry as possible. Note that the plaster hardening reaction produces a lot of heat, so be careful where you put it to cool, you could damage the surface under it.

Once the bat is dry, clean up any mess on the underside using a palette knife or similar tool. Try to make sure the underside is smooth and flat.

If using the P&S, mount the bat "key" on your wheelhead by removing and reinstalling your bat pins. It has some wiggle room, so carefully adjust it to make sure that the key is exactly centered on the wheelhead. Fit the bat to the key, securing it on top of your wheel. Now you can clean up your bat and add the foot groove (if you are).

First, take a large loop trimming tool or palette knife, and turn the wheel on to medium speed. Use the tool to trim and round off the edges of the bat.

If you're adding a foot groove, you'll want to carefully measure the correct diameter, centered, on the bat head using a t-square or other measuring device. Spin the wheel slowly to draw a circle at exactly the right diameter. Then remove the t-square and grab a sturdy round loop trimming tool (don't use your good trimming tools for this, but they do need to be at least somewhat sharp). Speed up the wheel slightly and use the trimming tool to slowly carve a semi-circular groove in the bat. You'll want this to be between 6mm/0.25" deep and 9mm/0.33" deep to make a good foot. It can't be a lot deeper with this throwing method, and you don't want it much shallower. Once you have a good, semi-circular groove, get a flat trimming tool and round and smooth the edges of the groove so that there are no sharp corners. Carefully remove and clean off all the plaster dust.

Now you're ready to throw on your new plaster bat with instant foot!

Note about the rack for my plaster bats, pictured below. Those bats weigh almost 10lbs each, so you'll need a sturdy rack to hold them. I found an adjustible pan drying rack online that worked for me.

One of the major drawbacks of having a pottery studio in a 1951 detached garage is the lack of running water. In the summer, I have an outdoor sink I run with a garden hose, but that's no good in the winter. I needed something that would allow me to easily wash my hands and small tools, with warm or at least lukewarm water. It couldn't require a lot of space, or a lot of electricity.

Now, there's high-end options like the Cink, but even if I had the $2000, I don't have the space.

Instead, I give you the $50 portable warm-water studio sink. No, it's not elegant, but it does the job for a tight space and a tight budget.

First, you're going to need to buy this particular electric pump faucet, which was recommended to me by someone on Clay Buddies. There are possibly other brands that will work, but you'll need to fit them yourself then. While you're at it, pick up another Clay Buddies recommendation: this aquarium heater (the 50W version; do not get a more powerful one).

Now, that faucet is designed to go on top of a 5-gallon water cooler bottle. Which is not what we're putting it on top of, so we need to manufacture a fitting. Which means ... on to the 3D printer! You'll need to print this design. If you don't have a 3D printer, I recommend PrintaThing (please do not contact me about printing one for you for hire; that's not a business I'm interested in).

You're also going to need a few other tools:

• 3.8" drill
• hacksaw or keyhole saw
• drill bits, including 1/8", 1/4" and 3/8"
• hole cutter (hole saw) drill bit, in graduated sizes up to 2.5"

However, it only requires a few other materials, some of which you may already have:

• A 5 gallon insulated beverage cooler (buy one now, they're on sale for winter)
• One wood, plywood, or strand board, around 15 by 19 inches and 3/8" to 3/4" thick, ideally painted or varnished to keep it from getting waterlogged
• Three #8 by 1/2" screws, preferably brass
• One 1.5" rubber stopper
• Four 12" cable ties
• One multi-outlet extension cord or plug tree
• A plastic washbasin, no more than 4.5" tall
• A large funnel
• A micro-USB charger

Now, first you need to use the saw cut a slot in the screw threads of the beverage cooler, so that you can slide down the cord of the aquarium heater and still screw the lid of the cooler closed. You'll need to cut a slot around 1/4" wide. Then slide the cord in, stick the heater to the bottom of the cooler, and run the cord to the extension cord. Fill the cooler most of the way with water, because after this refilling it will get significantly slower. Set the heater to 80F.

Now it's time to cut some holes! First, you're going to cut two holes in the lid of the beverage cooler (while it's off, so you don't get plastic in the water). One you'll drill with the 3/8" drill bit, which should be around 1.5"-2" in from one of the edges of the lid. The second one you'll use the hole saw for; you want to cut it around 1", but check what size it needs to be for that rubber stopper to fit snugly. The second hole should go opposite the first hole, and around 2" in from the closest edge.

Now you need to cut matching holes into the board. Use the lid as a template to mark the holes. One narrow end of the board should tangent the edge of the lid with the small hole; the big hole will end up closer to the middle of the board. Drill the small hole with the same 3/8" drill bit. For the big hole, you want to make it bigger than the one in the lid, so get a 2" or 2.5" hole saw and cut a bigger hole, centered on the one you drew.

Put the 3D printed faucet mount on the board, with its hole matching up with the 3/8" hole. Using the 1/8" drill bit, drill three pilot holes to match the screw holes for the faucet mount tabs. Drill these around 1/4" deep.

Time to assemble. Screw the lid on the cooler so that the small hole is at the back. Put the board on top, line up the small hole, and put something through it to hold it aligned. Make sure the big hole is also aligned. Get the 1/4" drill bit and drill two holes close to the edges of the board where they hang over the handles of the beverage cooler. Put the cable ties through these holes and the handles, at first loose and then gradually tighten them one at a time, tying the board into place.

Put the rubber stopper in the hole in the beverage cooler lid. Assemble the electic faucet, attaching its silicone hose, run the hose through the faucet mount, and fit the faucet onto the mount. Run the silicone hose through the board and the lid and down into the water. Use the three brass screws to fasten the faucet mount to the board. Plug the USB charger into the extension cord, and the USB cord into the faucet.

Put the plastic washbasin on the board. Press the button. You now have warm running water!

When you want to top off the water, move the basin, unplug the rubber stopper, and pour water in using the large funnel. I suggest pouring in already-warm water, or it's liable to take a long time to reheat. When the washbasin is full, dump it out in the yard.

Note that the silicone hose from the faucet will not reach the bottom of the cooler, so you can't use all the water. This is on purpose, so that the heater doesn't melt the cooler.

Since custom "logoware" is a significant part of my pottery business, I'm quite used to making custom "sprigs" so that I can stick people's logos, names, or other designs on thrown pottery. For a long time I've done this one of two ways: either I order a custom rubber stamp online and press it into a slab, or I sculpt a design out of clay and then cast it in plaster.

But now I have a new method, using 3D printing and silicone. Keep reading and I'll detail how you can use it too.

Why would I want to do something new? Well, both older methods have problems. The custom rubber stamps are expensive and slow to order, and never make a deep enough impression. Plaster is really annoying and time-intensive to cast with. And both methods involve some extra steps I'd rather not take: rolling slabs for the stamp, or prying the sprig out of the plaster before attaching (and possibly damaging it in the process).

So, let me show you the new method.

First, you want to design a 3D model on your computer that can be printed out. For folks just getting started, I recommend TinkerCAD, the free, simple 3D design program from AutoDesk. It's set up for this; for example, if you import a 2D logo or text into it, TinkerCAD automatically turns it into a 3D shape, ready for you to manipulate into a stamp.

Now, if you have your own 3D printer, you can then print this design yourself. If you don't, though -- and I don't recommend buying one unless you're ready for a new, time-consuming hobby -- you can get it printed via PrintAThing, a brokerage that contracts folks with 3D printers in your region to print and ship it to you cheaply and usually quickly.

You can also mold things you sculpted yourself, of course. I do a little of both, 3D printing logos and text, and sculpting things like slugs. Place your objects to be molded on a smooth, flat surface, far enough apart that you can cast each one separately. Like plaster molds, you want to avoid having too many undercuts -- but unlike plaster, you can have some, which is another advantage here. The flexible silicone can be pulled off of small undercuts.

Now, on to make the silicone mold(s). This will require 100% silicone caulk (and a caulking gun), some liquid food coloring (not gel), a whole box of corn starch, some disposable containers, and rubber gloves (you need these). You're making proto-putty per the video. Watch that for the method, which is to mix a couple teaspoons of food coloring into the silicone, then mix the sticky gel with the cornstarch until you can handle it.

There's another method of making moldable silicone using dish soap, but I haven't tried it. Lemme know if you do.

Then you press the moldable silicone, like clay, onto the objects you're casting. You need to move fast, because you have 10 minutes from the time you add the food coloring to work with it. You also have the tricky task of making the molds thick enough to be sturdy, but thin enough to be flexible. This is relatively easy with flat shapes like a logo sprig, but can be challenging with complex shapes like the slugs.

Then, you wait for it to set and harden. You can pry the objects out of the molds after only about an hour, which is useful to see if you got a big air bubble or similar and need to re-cast one. You should wait at least 12 hours before using any of the molds for clay, though. Once the molds are hard, you can also trim them with a serrated knife.

Now you come to the main drawback of using silicone: clay sticks to it. This means you need to powder the molds generously with more cornstarch before each use to get the clay to release. This can cause "stippling" on the molded design, so I'm looking at trying out some actual mold release agents instead, but for now I know cornstarch works.

After this, you should rough your pottery and the bottom of the molded clay with a toothbrush and some deflocculant like magic water, and then you stick the sprig directly on the pottery, bending the mold around the curve of the pot. That's the big advantage to silicone molds; you stick sprigs directly on your pots, eliminating prying & drying, and getting a better attachment & seal onto the pot in the bargain. It'll take you a few trials to get how to press the mold onto the pot (as well as keeping it oriented), so have some test pots to play with.

This works particularly well with decorations that need to be curved, like my infamous banana slugs: you're attaching them while the clay is wet and workable, so no cracking, and you can even pry up the edges so that undercuts (like the slug's mantle) come clear.

All of this was very easy to get started doing, and has completely replaced my old ways of doing sprigs. I hope it helps you too.

Oh, and if you want to buy one of those slug mugs, meet me at The OPA Holiday Sale this November 30th.