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Beer Bottle Master Mold via 3D Printing

April 2024: Version 3 of this method is underway and promises to be simpler and better than #1 or #2. And no very expensive urethane or silicone rubber is needed! Stay tuned.
May 2024: Version 4 is even better, natches are working, casting working molds directly from 3D prints.
June 2024: Version 5 now has a separate bottom (three-piece mold) so there is no seam. This enables embossed logo and variable heights using the same bottom piece.
July 2024: We are getting serious about producing these bottles in quantity for evaluation and helping others to do the same.

This project is being done to demonstrate the amazing power that 3D printing brings to potters who would like to adopt the slip-casting process for small-scale production.

It is now possible to quickly draw 3D objects on a computer, 3D print block or case molds and have working plaster test molds within a couple of days. The more pieces a mold needs to have the better this system works. It is interesting to note the precision that is possible using this process - and that achieving that precision can be done by simple trial-and-error cycles. Additionally, a potter can create partial or small-scale molds to prototype and then make full-size rubber masters.

Ceramic beer bottles were made historically. They are a very difficult shape for jiggering, needing to be done in two parts and joined. Thus, many companies even had teams of potters making them by hand. Slip casting using traditional mold-making techniques was never practical compared to the metal molds used in glass forming. That being said, ceramic bottles have some important advantages over glass - these include decoration and customization options, practicality for potters to make, flexibility to retool size and shapes, flexibility in glazes and colors and options for stamping and embossing. Ceramic glazes, especially stoneware glazes, also have the potential to be more durable. So it is easy to see why we are excited at how easy it now is for potters to take advantage of the ceramic process in ways industry cannot.

Version 3 coming: While a case block mold is ideal for a factory situation I am targeting this at potters. I found that the rubber picked up every imperfection of the 3D printed block mold and transferred them to the working molds. More fixup was thus required. And the rubber required reinforcing to produce right angles and perpendiculars. A plaster case mold seems to be best for moderate mold production.

This project uis long and arduous. I had to make just about every mistake to learn better and better ways of doing things. The best ways are turning out to be the cheapest - using the equipment that I have. My ability to do whatever is needed in 3D design is the single most important key to continued evolution of the process. I am cutting printing times dramatically by smarter use of the slicer and printing things in pieces and gluing them together.

Related Information

Slip cast leather-hard full-sized beer bottle prototype

The commercial bottle on the right is 25cm high. These stopper mechanisms are a commodity item, millions are made and a wide range of bottles work with them. They are easy to find online and go by a variety of names (e.g. "Grolsch style flip top stoppers", "Swingtop Grolsch style bottle cages", "Porcelain swing top cap").

The slip cast bottle is on the left - this one is leather hard, recently extracted from a mold. It is made using a black-burning stoneware, the L4768D recipe. The GA6-B glaze fires deep glossy beer bottle brown on this body. As a starting point, I used water/Darvan proptions outlined in the "Casting Recipe" section of the M370 data sheet. By the time this is fired it will be 10% smaller and will match the glass one on the right. The pads are positioned to work well with swing-top stoppers.

This GA6-B glaze is better than beer bottle glass

Ceramic glazes are actually just glass. But they are not like bottle glass. The latter is formulated to work well in forming machines (harden quickly), melt and stiffen quickly, have low melt viscosity and resist milkiness and crystallization on solidification. The chemistries to accomplish this have adequate resistance to leaching and adequate durability for a single or few uses. A stoneware glaze melt needs to be much more viscous (to stay put on vertical surfaces). And, it must have a much lower thermal expansion (to match common clay bodies). And, it must resist crystallization more much (since it cools slowly). Fortunately, meeting these needs brings along big benefits: Greater durability, hardness and resistance to leaching. Common target formulas express typical oxide formulas of glazes. Stoneware glazes and bottle glass share a common trait: They have about the same amount of SiO₂. But the similarity ends there, stoneware glazes have:

-High Al₂O₃. Three to five times more! It is the key oxide to producing durable glass. And it stiffens the melt (that disqualifies high levels from bottle glass).
-The same fluxes (CaO, MgO, K₂O, Na₂O). But they distribute very differently (half the CaO, half to one third the KNaO, much more MgO). Other fluxes like SrO, Li₂O are also common.
-Low KNaO (which they call R2O). In glazes it produces crazing, 5% is a typical maximum. But bottle glass can have double or triple that (the high thermal expansion is not an issue and its cheap source materials supply lots of melting power).
-B₂O₃ melter. It is expensive but can be justified because the glaze is just a thin layer. Glazes at the low end of the stoneware range have 5% or more boron.

The ceramic bottles shown here are made from a dark burning stoneware, the glaze is GA6-B. On the left is the same glaze on a porcelain mug. For the above reasons this glaze is more durable and leach resistant that regular bottle glass.

Making a mini bottle prototype mold

PLA is the most common filament used in consumer 3D printers. Because this is just a quick trial slip casting mold it is practical to print two PLA case molds (lower right) with vertical sides (it is impossible to remove the plaster mold from these without significant damage to the corners. But this is not a problem, PLA filament has a very low melting point so even hot water can soften it - I use a propane torch to heat them (very carefully of course) and they peel off easily. Making these confirms how accurate 3D printers are nowadays - the plaster mold halves mate precisely. Notice there are no natches, they are not needed for prototyping (lining up the outer edges perfectly positions the pieces). And there is no spare, we use a pour spout instead.

Testing the mini-bottle mold using a common casting body

I flush the edges around the mating surfaces, that automatically lines up the inner sections (so mold natches are not required here). This clay body, an M370C test, I made it by substituting OptiKast kaolin and KT#1-4 ball clay, materials intended for use in casting slips. This adjustment means that the slip only needs to stay in the mold for about 10-15 minutes to get a good thickness (vs 30 minutes for standard M370C). Within ten minutes after pour out the mold splits and the bottle releases.

Calibrating the fit for the stopper wiring assembly

In Fusion 360 I sliced off the top of the bottle and formed a small box around it to be able to quickly 3D print a test case mold of just the upper neck. Two of these printed in about 3 hours, I cast plaster mold halves from them. Making a hole in the middle of the wire mounts was easy at the leather hard stage. The wire is 2.8mm dia, a 9/64 drill bit is 3.5mm. Simply twisting it to create a hole in the center of the pads takes seconds. Firing these to cone 6 enabled testing the fit for the swing assembly. I followed this with two more iterations to perfect the pad size and hole diameter (ended up at 11/64").

The link below links to a step-by-step in Fusion 360 of how to save a temporary copy of the mold drawing and modify it to isolate just the top portion of the neck.

Proving the stopper on a fired piece

The centre one is M370 + 10% raw umber - leather hard out of the mold. The other two are fired at cone 6. Comparing the lengths of these two enables calculating the total shrinkage (drying and firing). I can use that to modify the parameters in the drawing. These fired tests were critical to adjusting the hole diameter and pad size - both were inadequate in the early design (notice, on the right, how the 9/64" leather hard size hole is breaking the pad when the wire mechanism rotates (because it inserts not quite perpendicular). Notice the pad is also too small. However, the hole being 21mm down from the rim is good, the mechanism is locking well.

How to draw a case mold for slip casting using Fusion 360

Drawing your objects in CAD software is the most difficult step in leveraging 3D printing for slip-casting. In this 11 minute step-by-step video, we will draw a case mold, using Fusion 360. It can be 3D printed and plaster poured in to make a working mold. Mold soap is not even needed. This method of quickly making a pilot mold is well within the reach of almost any potter.

Printing my own version 1 block mold in two pieces

Of course, this is far too large to print in one piece on my printer so I sliced it in two and added tabs to clamp the halves together. Notice the size rails are part of the print. The 3D rendered version was, of course, smooth but there is quite a bit of stair-stepping on the 3D printed surface, I did not worry about smoothing it and it did not prevent casting two plaster molds. No mold soap was even needed, the plaster molds came out using compressed air. The long side rails did require some stabilization (they were flexing with the weight of the plaster).

Finished cast v1 stoneware beer bottles

The center bottle is a standard glass one, the other two are ceramic, cast out of the version 1 plaster mold. The stopper fits perfectly. The clay is Plainsman M370 + 10% raw umber, it fires black. The glaze is GA6-B. They were fired using the C6DHSC firing schedule. The slightly larger size will enable inserts at the bases to inlay a logo or other info. These bottles are a testament to how 3D printing and 3D design now make it possible for even casual potters to make pieces never before practical or even possible.

Version 2 ceramic beer bottle rubber block mold

This time I printed the block mold, rather than the case mold, in six pieces on my consumer 3D printer.
Top: I printed the two halves upright (creating them in the slicer rather than Fusion 360). Because the print lines run concentric the quality is so much better than the previous version printed flat. The ribbing inside made the halves strong so they did not go out of shape when filled with plaster (to give them weight).
Second: The mold halves were simply laid against each other - they mated perfectly (and stayed in place because they are full of plaster). The four rails were then clamped in place.
Third: The PLA was soaped (using Murphy's Oil Soap) and rubber poured in (Smooth-On PMC-746). The next day it easily pulled out.
Fourth: The finished rubber case mold. The sides are pretty flabby so I make them rigid using the four rails (placed upside down).
Right: Using a plaster mold created from this rubber case mold I slip-casted a bottle using my L4768D recipe, glazed it with GA6-B and fired it at cone 6.

Yikes - Version 3 ceramic beer bottle drawing mold obsoletes previous

Something I love about 3D parametric CAD is how a drawing can evolve to be both simpler and better. While my version 2 drawing had about 20 steps, this one is down to nine. No more ribs, no offsets or mirrors in the sketches, no double-revolves and no seams across the mount ads. Printing will be dramatically faster. The quality of the side rails is now the key factor in final mold accuracy (these stabilize it while filling with plaster from the back).

I now draw the simplest repeatable shape: A one-quarter slice. Step 5 cuts the bottle profile from the solid block extruded in step 4. The preceding steps were a sketch of the bottle and block outline and a plane and sketch for the pad. Steps 6 and 7 are the extrusion and corner rounding of the pad cutout (near the rim). The last two steps mirror this quarter upward to create the block and then shell it to hollow the back side.

The drawing is now fully parametrically resizable, I have taken advantage of that to make a stubby bottle test. Neck spline points are now spaced vertically as a percentage of the neck height parameter - set at "70" here. The body and neck heights are separately set now so the full height is now a driven dimension - it is 146 here.

Three-piece vertically printed mold with natches

These 3D prints slide into slotted side rails for each pouring of plaster. Since the plaster releases easily it is possible to use these multiple times. This method is suitable for prototyping in larger quantities than prints that integrate rails. These are printed on edge so print times are drastically reduced and surface smoothness is much better. This version has a bottom piece eliminating the seam across the base. It also enables putting embossed logos on the base. The holes enable mounting flush embeds - making it possible to sand the mating surfaces flat before gluing in the natches. The three-piece mold produced is shown on the bottom.

Pouring the v4 plaster beer bottle mold

This project is a testament to my wife's patience with me using her kitchen as a mold making shop. Most of the tools I need are there. A nice stable table to run two 3D printers, lots of room and plugins, electrical appliances, utensils and supplies of every type, good lighting. And pleasant company!

I have already poured PMC-746 rubber into 3D printed block molds and have printed and put in place stabilizers to hold the rubber in place. Embeds are in place on both the bottle base and bottom mold (upper right). The flexibility of this rubber is amazing, it makes possible extraction of the plaster base, although with difficulty. It also preserves the embossed logo on the foot. This is version 4 (version 5 will have a shallow base piece and modified sliding natches).

The $5 garage sale mixer does not pull bubbles to the surface so I just pull them up by counter-stirring with a serving spoon. A common sense workflow (never pouring any down the sink, cleaning everything in a settling bucket) makes this no problem in the kitchen.

Slotted natches make this bottle mold possible

These enable pulling apart the top halves of our ceramic beer bottle molds while the leather hard bottle is still embedded into the base. Starting upper left and clock wise:
#1 The 3D design for making a rubber case mold.
#2 It has been 3D printed in three parts (which are then glued together).
#3 PMC-746 rubber was poured in and the 3D printed parts were peeled off.
#4 Natch parts have been 3D printed.
#5 The embeds have been rubber cemented onto the rubber mold (to hold them in place during casting).
#6 Plaster was poured in.
#7 The plaster working mold has been extracted from the rubber, the embeds firmly rooted in place.
#8 The slots have been epoxied in place (lined up and positioned accurately so the natches hit the end of the slots just as the halves contact).
Centre: The mold partly assembled.

Inbound Photo Links

Why 3D design and printing is a better way to make slip casting molds

The bottle is more important than the beer!

Regular bottles of beer looking very humble beside the ceramic one

Links

Media	Make a precision plaster mold for slip casting using Fusion 360 and 3D Printing In 11 minutes you will learn a new way to make complex plaster molds for slip casting - faster and more precise than ever before. Anyone can do this.
Media	3D Print a Test of the Beer Bottle Neck In 4 minutes you will learn how to modify a copy of the existing drawing to print only a narrower part of the top 8cm
Media	Slip cast a stoneware beer bottle I will mix the slurry, assemble the mold, attach the 3D-printed pour spot, pour in the slip, pour it out, remove the spout, trim the lip, split the mold, extract the bottle and drill the holes for the swing-top stoppers.
Media	Design a Triangular Pottery Plate Block Mold in Fusion 360 Lilly will take you step-by-step through the process of parametrically drawing a triangular plate with curved sides and rounded corners, for 3D printing to pour a plaster working mold.
Projects	Medalta Ball Pitcher Slip Casting Mold via 3D Printing A project to make a reproduction of a Medalta Potteries piece that was done during the 1940s. This is the smallest of the three sizes they made.
Projects	Nursery plant pot mold via 3D printing
Glossary	3D Design 3D Design software is used to create dimensionally accurate objects by sketching 2D geometry and transforming it using tools to rotate, extrude, sweep, etc. The software generates the polygon surface.
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!

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