Click here for information about DIGITALFIRE Corporation

Monthly Tech-Tip from Tony Hansen

I will send practical posts like these (from thousands I maintain). No ads or tracking. We are troubleshooting the confirm email, for now you will be subscribed immediately (the first monthly email will provide one-click unsubscribe).


Blog

Oversize Particles Simple Test

Oversize ceramic materials particles on 150 mesh screen

This is simple test can be done to determine if oversize particles are present in a raw material to be used for clay body manufacture. While materials are sold as minus 200 mesh, as you can see here, they don't even pass at 150 mesh. In each case, we have attempted to wash through 50 grams of the powder (using the technique of our WSR test).

All ceramic materials must be ground using particle size reduction equipment. This process enables removal of contaminants or reducing their size enough that they do not marr the fired surface of the body. This is a demanding task. Being able to measure it quickly enables spotting problems with a materials shipment (and therefore how well a supplier meets their quality obligations and the kind of product that can be made using it). Ball clays and kaolins are the most problematic, not just in particle size and contaminating particles but also fired color and plasticity.

Of course, a record of this needs to be kept. That is where your account at Insight-live.com comes in. Upload pictures like these or just make a note of the result.

Context: Wet Sieve Residue, Watch out for iron..

Tuesday 1st July 2025

v6 Beer Bottle Drawing

Fits standard swing top stoppers.

Available on the Downloads page

3D printed case mold for making ceramic beer bottles

3D print this, pour in plaster to make a slip casting mold! My previous work on this project assumed a smaller 3D printer (making it necessary to print flanged PLA mold sections that clip together). But larger 3D printers are now common, making the CAD work much easier. This drawing is parametric for height, body diameter, wall and plaster thickness, and neck height (for the full bottle set body=160mm, neck=96). This uses my standard clips and embeds (upper right). Neck vertices are proportional to height, so resizing works well. The top end is filleted to permit the longest possible mold on the print bed (diagonally). The bottom inside perimeter is chamfered, strengthening the default 0.8mm side wall junction to the base (that being said, be careful when removing it from the print bed, flexing too much will cause failure here).

Doing this smaller size is for prototyping and testing. Note that casting plaster on a 3D print creates artifacts (which will appear as wood grain, lower right), later I will create a hybrid plaster/PLA or rubber case mold. This PLA mold prints quickly, it has a hollow back side, permitting easy removal with a heat gun. There is no spare, it employs a pour spout, making the mold shorter and producing a better lip.

Need a stoneware slip casting recipe? L4768E or L4768H are a good choice. A glaze recipe? How about GA6-B (or similar)? Go full DIY with this, you will never turn back.

Context: Swing Top Stopper Mechanism.., A 3D Printed Mold.., DIY natches spacers and.., Here s my setup.., Beer Bottle Master Mold..

Monday 30th June 2025

A 3D Printed Mold Spout

Better Than a Spare for Slip Casting

Available on the Downloads page

A plaster mold pout spout

Glue one of these on top of your slip casting mold (using slip) and enjoy the many benefits. These are intended for people who make their own molds using the 3D printing techniques taught on this website. Among the advantages are the following:
-Less mess.
-Smaller, simpler molds (they don't need a spare).
-Overhung lips, more precise lips.
-Visible indication of casting progress.

Context: v6 Beer Bottle Drawing.., Pour Spout

Sunday 29th June 2025

Here’s my setup for pouring plaster in the kitchen

Making plaster molds in my kitchen

Because of the ease of 3D printing case molds at home I can now pour plaster in them also. Of course, I am not in production; this is about creating prototype molds. This technique makes it possible to be precise in the amount of plaster used, so there is almost no waste. My tools are simply a good propeller mixer, and a scale and a 3-D printer (and a cooperative wife). Here is my procedure:
-Counterbalance a plastic container.
-Fill the mold with water and pour into the plastic container to get the weight in grams (and thus cc's).
-Plug that weight into https://plaster.glazy.org, set it to use centimenters and get the USG recommended weights for plastic and water.
-Put that amount of water in the flexible plastic container and tare it.
-Dump in the plaster needed (no need to sprinkle it, I have a good mixer).
-Set the timer for 4 minutes and let it soak.
-Put it under the mixer (at an angle as shown), set the speed to create a whirlpool just shy of pulling in any air (thus avoiding adding bubbles). Mix for 4 minutes and then pour it into the molds.
-Clean the mixer blade and shaft in a container of water (and throw that away outside). Let the plaster harden in the plastic container (it breaks away cleanly later).
-Let it set overnight and use a heat gun and pliers to carefully remove the PLA from the plaster.

Context: A high-quality inexpensive studio.., A 1g electronic scale.., v6 Beer Bottle Drawing..

Sunday 29th June 2025

20 Skids of Material Just arrived

Fearful Freddie doesn't know what to do!

Fatique Freddie is overwhelmed by incoming material

Fatigue Freddie is scared. His company doesn't take responsibility for product quality variations resulting from material variations. But when it happens he gets blamed anyway. Production wants to start using it tomorrow! He doesn't test all the product runs they make. He doesn't test incoming materials. He doesn’t know how he would handle the mountain of data that world produce, or how to learn from and act on it. Plus he's alone, there is no cooperation between production, sales, QC in feeding info into any kind of record-keeping system.

Minimal testing: Give the shipment a new code in the recipe area of Insight-live. Enter what is known. Upload a picture of any certificates provided with it. Are all the pallets lot numbered? Record that in the notes. Are they all the same lot? Record that. Are the pallets sequentially numbered? Test one from each lot for oversize particles (very important for clays). Make an SHAB test bar also, get it/them dry (in the dehydrator) and into the kiln overnight.

Context: Wet Sieve Residue, Protect your reputation as..

Thursday 26th June 2025

Absolutely Jet-Black Cone 6 Engobe on M340

The could also be super white

A buff stoneware mug with black engobe

This is the L3954B engobe. 15% Mason 6600 black body stain has been added (instead of the normal 10% Zircopax used for white). Of course, a cover glaze is needed for a functional surface. We put a lot of development work into producing a recipe fits this body, M340. It works even when thickly applied because it has the same fired maturity as the body. Lots of information is available on using L3954B (including mixing and adjustment instructions). Engobes are tricky to use, follow the links below to learn more. L3954B is designed to work on regular Plainsman M340 (this piece), M390 and Coffee Clay. Most important we document how to adjust its maturity, and thus firing shrinkage, to fine tune fit if needed. These bodies dry better than porcelains and are much less expensive, so coating them with an engobe to get a surface like this makes a lot of sense. Ed Phillipson discovered this 80 years ago, enabling selling ware made from these clays as white hotel ware.

Context: Mason 6600 Black Stain, L3954B, L3954J black engobe on.., How to make a.., Here is why porcelain.., How to test if.., Stained engobes can be.., The L3954B engobe page.., Thixotropy, Engobe

Wednesday 25th June 2025

In-plaster Anchors With Threaded Inserts

Available on the Downloads page

M3 3D printed threaded inserts for plaster

These brass/plaster pyramids embed into plaster to provide a threaded hole that M3 bolts can screw into. That enables attaching 3D printed elements to plaster elements when making hybrid molds. Narrow inserts permit placement in cramped spaces and nearer edges.

These are made possible using M3 brass knurled nuts and M3 bolts that can be purchased on Amazon. The brass nuts can be pressed in using a soldering iron. The pyramid-shaped 3D-printed anchors are 13mm high, they will accommodate 12mm, or less, inserts (the longest ones in the kits shown here bottom left). The holes are 4.4mm dia at the top and taper inward at -2 degrees. Of course, you can adjust sizes and angles as needed for your application.

Context: Hybrid plaster 3D printed..

Wednesday 25th June 2025

The amazing power of 1% talc:

It accelerates the vitrification of this stoneware

1% talc added to a clay body

These two unglazed pieces are made from the same clay, M340. They are fired at the same temperature. But the one on the right has 1% talc added. Greying of the color is a characteristic visual change as this clay body transitions into the vitreous state we target. That transition happens over a narrow temperature range. Because the raw materials naturally vary in the temperature at which they vitrify, we have to tune the recipe so that the transition happens from cone 5 to cone 6. It is accompanied by a drop in porosity of 2% or more (according to our SHAB test). Talc acts as a catalyst for this change; in this case, only 1% is needed. By itself, talc is refractory. Yet it acts as a flux here! The fact that it can effect this big of a change with only 1% is amazing. Interestingly, this phenomenon only occurs with tiny talc additions.

Context: Talc, Vitrification

Wednesday 25th June 2025

TPU vs PLA Filament for Mold Making

TPU vs PLA for mold making

The mold on the right is PLA filament. Printed at 0.8mm thickness, it only weighs 38g yet is very strong. It removes easily from the plaster with a heat gun. The TPU flexible mold weighs 62g (the walls are 1.6mm thick) but it will need a PLA shell to hold the walls vertical (or far thicker walls). It took four attempts to print this. The surface quality is not nearly as good, especially on the top layers. Printing is much slower.

PLA is a bioplastic, made from renewables. It can potentially be composted. PLA is the most common type of filament used in FDM 3D printing. It has a low melting point, which eases printing and improves interlayer adhesion (but heat resistance of printed products is poor).

Regarding TPU, here is some advice from a follower (who uses a Prusa printer and gets better results than us): "The secret to printing with TPU is constant speed while printing. Under Print Settings, go to Speed. Set them all to 20 mm/s. Ironing will be greyed out unless you have it on. Then, in the next section, Dynamic Overhang Speed, set everything to 20 mm/s. Under Modifiers set First Layer Speed to 20 mm/s. Then under Auto Speed (Advanced), set Max Print Speed to 20 mm/s. This will prevent almost all webbing and other print issues. Some people also suggest reducing the Z-Axis Nozzle Retraction, but I have not found a need to do that."

Context: PLA 3D printer filament..

Monday 23rd June 2025

Vevor Potter's Wheel for $175.

Can this be real? What am I missing?

Pros: -It actually does work well. -Metal construction (plastic foot pedal), bottom panel removes easily. Foot pedal is easy to open and fix. Motor is standard and easy to get. -The wheelhead and pan are similar in size and quality to standard wheels. -Easily purchased online at Amazon or Vevor.com (.ca in Canada). Cons: -Small, too light, be prepared to make leg extensions, a platform or use it tabletop. -Power limits how much clay can be handled, likely 5 lbs or less (for novices, this is less of a limitation). -Not bat pin holes but they could be drilled easily (or other methods of holding bats in place could be used). Understanding the main reason this is so inexpensive is important to appreciate it's limitations. Typical wheels have AC motors with relatively complex electronics to control their speed (these combos are expensive). This wheel employs a stepper motor. These move in tiny, discrete steps and are perfect for things like robots and 3D printers. However, they can be force-fit to continuous motion (by the electronics delivering constant step-pulses). But pulse frequency must be gradually increased and decreased to ensure the motor does not miss any steps. Other issues: Stepper motors exhibit resonance at certain operating speeds (controllers need to move through these zones quickly) and torque changes in a non-linear relationship to speed (top speed is thus limited). Success thus depends on smart electronics to convert the variable voltage from the simple potentiometer in the foot pedal to pulses the motor can handle. It is unclear how repairable this is, more info coming soon.

Context: Vevor Pottery Wheel footpedal..

Sunday 22nd June 2025

Contact Me

Use the contact form at the bottom on almost all the pages on this site or let's have a together.

Other ways to Support My Work

Subscribe to Insight-Live.com. It is about doing testing and development, not letting the information slip away. Starts at $15 for 6 months.

Help Me on Social

Tony Hansen
Follow me on

Test, Document, Learn, Repeat in your account at insight-live.com

Login to your online account

Chemistry plus physics. Maintain your recipes, test results, firing schedules, pictures, materials, projects, etc. Access your data from any connected device. Import desktop Insight data (and of other products). Group accounts for industry and education. Private accounts for potters. Get started.

Conquer the Glaze Dragon With Digitalfire Reference info and software

Download for Mac, PC, Linux

Interactive glaze chemistry for the desktop. Free (no longer in development but still maintained, M1 Mac version now available). Download here or in the Files panel within your Insight-live.com account.


What people have said about Digitalfire

  • Thanks again for all you have done for the pottery world!!!
  • Am finding your website a treasure trove of extremely thoughtful writings for the aspiring more-technical studio potter. Thanks for putting it out there.
  • I have found the glaze information on your site really helpful for quite some time now. I like the way that there is an emphasis on problem solving and understanding how things work, rather than just offering recipes that might work.
  • I would also like to say thank you for providing the information about glaze's that you have on your websight. I have been formulating glaze for 20+ years, read practicaly every book on glaze & glass and your web page's had better information than any book.
  • However I do believe you have the most comprehensive information anywhere in the world, and I would not hesitate to contact you for any information I required for Ceramic Glaze. I will also refer my associates to you if ever they require assistance.
  • Thanks for sharing so much great information!
  • I feel your information about majolica and glaze adaptation is the best I've seen anywhere and I do understand I need to do the testing and find what works for my situation.

What people have said about Insight-Live

  • As a side note: most of the students did access your information in their presentations. I found it interesting that your work is becoming foundational.
  • With a major in ceramics i have been working in the glaze lab of a big sanitary ware production company for about 3 years now. I want to tell you how much i appreciate the work that you do and the knowledge that you share, through out the 7 years that i have been studying and working in the Ceramics field. You have been the most important source of knowledge for me no one has ever taught me as much as you did through digitalfire. I truly love ceramics its quite a beautiful field to work in and i love and excel at what i do and big part of that is because of the guidance that you provide. And that really means alot to me to see a research or a test work out as i planned.
  • How amazing it is to have personal contact on such an amazing technical site and I can’t express my gratitude for your generous spirit.
  • Anyway I thank you for your efforts in putting together this wealth of ceramic science in this accessible manner.
  • I am a high school senior AP ceramics student investigating glaze chemistry and rheology. I spend a great deal of my free time browsing the digitalfire reference library, and would have never developed the passion I have for ceramics chemistry had I not come across it.
  • Thank you! Tony for all of the impressive work that you have contributed to our industry over the years. Your glaze work has been super helpful.
  • You have such a brilliant analytical mind, able to find solutions to many ceramic problems. You have accomplished so much in your life, helping us potters understand what we are doing. I cannot thank you enough for your vast ceramic reference library online. I think you are a national treasure.



https://digitalfire.com, All Rights Reserved
Privacy Policy

1