A One-speed Lab or Studio Slurry Mixer

Description

A single-speed lab mixer can be made for much less money than buying a commercial unit. Using it you can slurry up a 100 lb batch of porcelain powder in minutes and it will be smooth as silk.

Article

A one-speed lab mixer used at the Plainsman Clays lab/studio. This can be made for much less money than buying a commercial unit. However, remember that this is single speed. Check the pictures below to see how it is made. Using a powerful mixer like this you can slurry a 100 lb batch of porcelain powder in minutes and it will be smooth as silk, no lumps at all. Then pour that, in batches, onto a plaster table (see link below to make your own 350 lb plaster table) and you can have ready-to-use clay in hours.

To make a unit like this, print the pictures here and take them your local equipment supply outlet, hardware store, or even farm supply store. For safety's sake, do not take shortcuts, especially with the water-tight switch and electrical.

Warning: This is a very powerful motor and there are no guards on this unit. You can be seriously injured using this mixer if you are not diligent. Here are some guidelines:

When picking the mixer up, make double-sure the switch is fully off and grasp it in such a way that you have a finger holding it in the off position.
Never plug it in without first checking that the switch is off.
Make sure it is very securely mounted before leaving it running without supervision.
If you are holding it while mixing, keep one finger on the on/off switch at all times so that you can switch it off quickly. Only operate it if you are standing directly over it and have it in full control. Do not try to lift and operate it if you feel it is too heavy for you to handle.
When you start the mixer, be ready to turn it off immediately; it is powerful and may cause the slurry to overflow the bucket edges.
Use a good quality bucket that cannot be punctured by the propeller.
Never allow a child to use it and do not let anyone else use it unless you have briefed them.

Related Information

Heavy duty mixer mounted on a steel pole

It is adjusted so the shaft is at an angle (rather than straight up and down) to pull less air bubbles into the slurry. It can mix up to 5 gallons of viscous glaze or body slurry. The motor is very powerful enabling the mixing of low water content slurries (this means that amounts of less than about 2 gallons of slurry can splatter quite a bit). The 1/2 inch shaft is 22 inches long and the propeller is mounted up from the end of the shaft.

One-speed slurry mixer mounting clamp

An aluminum C-clamp adjustable-angle motor mount secures the mixer motor and mounts it to the custom-made arm extending from the steel pole. The switch also mounts to it. This may be so easy to find, but if you show a picture at a hardware store they should been able to recommend an alternative mounting strategy.

One-speed slurry mixer mounting mechanism

Rear view of how motor and switch attach to aluminum mount.

One-speed slurry mixer motor label

Mixer motor specifications label. Show this at an equipment supply store and they will be able to give you this exact motor.

One-speed slurry mixer switch close-up

Wet location sealed switch used on mixer. The electrical-in is sealed using silicone.

One-speed slurry mixer motor-shaft coupler close-up

The coupler used to mount the 1/2 inch stainless steel shaft to the motor shaft. It uses 4 Allen set screws to hold it tightly onto the shafts. The two shafts are not the same diameters, so you may have to have this made at a local machine shop.

One-speed slurry mixer propeller close-up

4 inch propeller (2 inch radius) mounted on a 1/2 inch stainless steel shaft. It is not mounted right at the bottom, this is done to prevent the blade from contacting the bottom of the bucket during mixing. By googling the identification you see on this prop(Taiwan 4x4 316 propeller) you would find the site of the manufacturer (http://www.tonson-motor.com/e/p004.htm).

3D printed plastic and stainless steel propellers

Plastic and stainless steel 3D printed propeller side-by-side

I had this done at Shapeways.com. They offer an after-print polishing service, which I did not get. The plastic one on the left (actually printed from PLA filament) weighs 5 grams. The steel one weighs 45 grams! It cost $35 to print this. The quality is like regular stainless, this is incredibly hard! Fitting it on the shaft was the first issue. The shaft measures 8mm. My drawing sets the hole at 7.9mm (5/16"). On the 3D print with PLA I got 7.8mm, but this this arrived at 7.7mm. It required a lot of work to enlarge the hole to fit. Thus, if I were to print this again, I would set the drawing at 8.2. That should either fit or only require enlarging the hole slightly (using emery cloth). The second issue was the hole and tap for the set screw. Drilling it was very hard, the first bit broke. The second made it through, but we could not tap the threads. So we will glue it to the shaft. Do you have a suggestion on a better way to fix it to the shaft? Please let me know.

See the magic of thixotropy as I mix a 20kg batch of G2926B glaze

In this video, I mix 20kg of glaze powder into 20kg of water using our powerful propeller mixer. The resulting slurry is like water, absolutely unusable. Yet on measuring the specific gravity (using a hydrometer because it floats freely) I find that it is too high, I actually have to add more water! How is that even possible? Instead, I add Epsom salts and mix again and the slurry gels and hangs on in a perfectly even layer when I dip the spatula. This is a thixotropic gel, it will apply evenly to bisque ware yet not go on too thickly. We normally recommend a specific gravity of 1.44 for this glaze, but in this case, it seemed watery enough at 1.46 (on use, it will become clear if 1.46 is OK e.g. if it goes onto the ware too thick). If that happens I'll just add water to 1.44 (and more Epson salts if needed). At the time of writing, based on online pricing at this time, coverage is 650-5000% cheaper than buying jars of transparent brushing glaze (I am considering both the total powder weight and the specific gravity difference between this and commercial glazes we use).

Links

Glossary	Propeller Mixer In ceramic studios, labs and classrooms, a good propeller mixer is essential for mixing glaze and body slurries.
Glossary	Plaster table

By Tony Hansen
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