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

3MF vs STL vs OBJ files for 3D printing

STL, OBJ and 3MF files

Shown here are Creality Slicer, Prusa Slicer and Simplify 3D. Each of these can import STL, OBJ and 3MF files. Each permits resizing, rotating, reflecting and duplicating individual items and can efficiently place and space multiple items and groups. Each saves or exports as 3MF files. On the right is the Fusion 360 print dialog where I can choose which slicer and which format to send.

OBJ files were introduced in 1980 for visual rendering (e.g. animation, gaming, special effects). Files store surface geometry as interconnected triangles and define surface textures, materials and colors. These features were overkill for early 3D printers.

STL (Stereolithography) files were developed in 1987 by 3D Systems specifically for CAD and 3D printing, having a single focus on geometry. They were simple and computationally efficient (and also unitless like OBJ, assuming mm). STLs permitted only one object. They dominated early 3D printing processes (FDM, SLA, SLS), where color or texture was irrelevant and provided a simple standard for industry growth. However, modern printers can now do color, texture and multi-material, thus...

3MF (3D Manufacturing Format) files were introduced in 2015 specifically for more advanced 3D printing. To OBJ they add object orientation, units, printing instructions and meta information. Objects in 3MF files can be manipulated separately in the slicer.

All three formats are generated by modern CAD software (for handoff to a slicer app). 3MF is the preferred one.

Context: 3D Design, 3D Slicer

Thursday 16th January 2025

Can you actually throw a Gerstley Borate glaze? Yes!

A thrown vase made of a Gerstley Borate glaze

G2931 Worthington Clear is a popular low to medium-fire transparent glaze recipe. It contains 55% Gerstley Borate (GB) plus 30% kaolin (GB melts at a very low temperature). GB is also very plastic, like a clay. I have thrown a pot from this glaze recipe! This explains why high Gerstley Borate glazes often dry so slowly and shrink and crack during drying. When recipes also contain a plastic clay like this one the shrinkage is even worse. GB is also slightly soluble, over time it gels glaze slurries even in smaller percentages. Countless potters struggle with Gerstley Borate recipes.

Context: Gerstley Borate, Gillespie Borate, Gerstley Borate 5 3.., Gerstley Borate vs Frit.., Replacing the Gerstley Borate.., Glaze Gelling, Plasticity

Wednesday 15th January 2025

Closeup of the polygon surface of a cast mug

Freshly slip cast mugs

This is L4023F (a test body like our H440 cone 10R body). The polygons on this surface are produced when the 3D CAD software converts from its native format to an STL file that slicer software can use. These are the product of the default settings (which can be changed but increase file size). The precision of the 3D printer is evident in that it can reproduce these. Since the polygons are not visible in the final glazed piece, neither the PLA surface on the 3D printed block mold, or the surface of the plaster case mold made from it, were sanded.

Context: First mug case mold.., Coffee Mug Slip Casting..

Thursday 9th January 2025

Which common American/Canadian feldspars can substitute for each other?

Feldspars melting

Feldspars are employed in glaze recipes as melters. So comparing their melt fluidities should be helpful in deciding if one can substitute for another (of course, if possible a soda predominant feldspar should be substituted for another soda spar). Feldspars don't melt alone at cone 6 (2200F) so we mixed each with 15% Ferro Frit 3195. Nepheline Syenite is obviously the champion melter here. Other similar ones can be spotted easily. In the end, degree of melt is a valid consideration in determining if one feldspar is a viable substitute for another in a recipe. Even if the feldspar you want to substitute does not melt as much a little frit can be added to the recipe to make up for the difference (e.g. 3-5%).

Context: Nepheline Syenite, Covia Nepheline Syenite, Minspar 200, Mahavir Potash Feldspar, G-200 Feldspar, Kingman Feldspar, Custer Feldspar, Feldspar, Calculating a substitute for.., Feldspar Glazes, Material Substitution

Thursday 9th January 2025

3D-printed cookie cutters used to make this tile design

3D-printed cookie cutters to make fish tiles

Only three tile shapes were needed. The fish cutters were 3D printed to both cut and stamp at the same time. Multiple slightly different sizes of the triangle and trapezoid were made to accommodate irregularities and keep joints tighter. The clay is M340 and the glazes are Amaco Celadons and Potter's Choice (for brushing). These are small and we found that a good way to paint them was to glue them down to a plaster slab with a few drops of glaze (it was easy to scrape off when the three coats had dried).

Context: Magic tile shape grows.., Video Create a cookie.., Cookie Cutting clay with..

Thursday 9th January 2025

This is crazing. This is functional ware. Is this good?

A crazing glaze on a porcelain mug

This glaze is "stretched" on the clay so it cracks. When the lines are close together like this it is more serious. If the effect is intended, it is called "crackle" (but no one should intend this on functional ware). Potters, hobbyists and artists invariably bump into this issue whether using commercial glazes or making their own.

"Art language" solutions don't work, at least some technical words are needed to understand it. Crazing is a mismatch in the thermal expansions of glaze and body. Most ceramics expand slightly on heating and contract on cooling. The amount of change is very small, but ceramics are brittle and glazes are rigidly attached. If they are stretched on the ware cracks will occur to relieve the stress (usually during cooling in the firing but sometimes much later). All glaze manufacturers advise against crazing on functional ware.

Context: Where do I start.., Two matte mechanisms One.., Two ChatBots square off.., Glaze Chemistry, Glaze Crazing, Glaze Crazing

Thursday 9th January 2025

Two ChatBots square off on crazing in 2025

ChatGPT vs Gemina on crazing glazes

In 2025 ChatGPT’s four glaze adjustment suggestions are either wrong or will accidentally fix crazing because they address other issues that just happen to also be present. Adding enough silica or alumina brings unacceptable side effects on multiple fronts. Alkali fluxes need to be substituted, not reduced. Simply substituting frits changes the overall chemistry making it a different glaze - why not just use a recommended recipe for the body as suggested by Gemini? Adding silica to a body increases, not decreases, the thermal expansion (and it reduces vitrification). Increased vitrification doesn’t make the body resist crazing (bodies don’t craze) - unless increased vitrification happens to also increase the thermal expansion (but not introduce warping). Slower cooling or a lower refire only delays crazing. Comparing COE’s of body and glaze is impossible for anyone not having a dilatometer to test both (you cannot compare measured and calculated COEs and calculation of COE for bodies is impossible). Embracing the crazing is a no-go for functional ware.

Gemini correctly explains why it happens. But, it suffers similar misconceptions about vitrification, cooling, silica additions to the body, vitrification and ignores the side effects of increasing silica or alumina in a glaze recipe. It is right that alkalis need reduction, but fails to note what to substitute. It recommends zinc as a stabilizer (whatever that means), but zinc is a strong flux that should be substituted for KNaO. Thinner glaze coating just delays crazing. Its suggestions about experimenting, keeping records, and researching to find recipes known to be compatible with the body are good. The only information available from glaze or body suppliers that might help is a chart that permits ordering products from lowest to highest COE (enabling you to at least transition in the right direction for better fit).

Context: This is crazing This.., ChatGPT was completely wrong.., Calculated Thermal Expansion, Glaze Crazing

Saturday 4th January 2025

Melt fluidity is not evident on typical glaze tests

Measuring melt fluidity of a matte glaze

We wanted to compare the melt fluidity of G2934Y (left) to G2934 (right). To do that we prepared GBMF test balls (see below). The forming and drying process leave a flat spot so the gumball-sized balls are easy to place on a porcelain tile. During firing they flatten out. The degree to which they do acts as a measure of the flow (when compared with another). Many characteristics that one would not observe on glaze tiles reveal themselves in this test. In this case, we needed to know if the melt flow was at least as good (and this proves it is better). Reactive glaze tend to be the norm in recent years, their primary characteristic is being runny (having high melt fluidity). Their fired character...

Context: Preparing balls for a.., Forming a glaze into.., Melt Fluidity

Tuesday 31st December 2024

Reactive glazes are good. And bad.

Reactive glazes don't melt into a homogeneous melt and they don't freeze as a typical glass. The physical nature of the material powders (e.g. their particle size and the individual nature of how they respond to heat, soften, melt and interact with their own kind and others) create a melt that does not solidify into a homogeneous glass. These glazes are said to be dynamic. And unpredictable effects often occur during firing, like color variegation, speckles, streaks, mottled and flowing textures, crystallization, pooling, etc. The outcome is influenced by factors such as the materials chosen to source the needed oxides, firing schedule, kiln atmosphere, cooling or heating cycle, etc. These glazes are at their best when each piece has a unique, artistic character. But, this is also their worst feature, making them "tipping point glazes", ones whose visual character is a product of fragile and not well understood features of the materials and process. Small changes typically produce big changes in fired appearance (often to the chagrin of the potter).

Context: Reactive Glazes

Tuesday 31st December 2024

A high-quality inexpensive studio/lab mixer is here

Inexpensive Fristaden lab mixer

For many years we have searched for a credible alternative to our Lightnin lab mixer. We found this unit on Amazon but then bought it from FristadenLab in Nevada. These are made in China but packaged, documented, shipped and supported in Nevada. This cost about $300US (a programmable one costs a little more but this is the better option for ceramic slurries). The first impression is how heavy the unit is. The base is 1/4" solid steel. The rods are all solid stainless 5/8". The clamp is also solid metal. The shaft is 3/8" and is held in place by a good quality chuck which enables easy release. The propeller is about 2 1/2" in diameter and screws on, it would thus be easy to 3D print other propellers and mount them on a hex nut (e.g. to fit into glaze jars). The locking mechanism enables mounting at an angle (important when trying to achieve the highest speed without sucking air bubbles). It plugs in via a 24v DC adapter (which means it has a DC motor). When switched on it speeds up gradually and the dial offers fine control of speed. On this occasion, we mixed 3500g of plaster in this 2 IMP gallon bucket (2.5 US gallon) with no problem. It runs completely silent and should easily mix this pail full of glaze or casting slip. A propeller mix like this is a great start to DIY glazes.

Context: A must-have Laboratory variable.., Learn to draw and.., Based in the USA.., Propeller Mixer

Tuesday 24th December 2024

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

  • I must say I am amazed by what I saw here. I am even more surprised to see so much of cermaic material stuff here.
  • Your web is great!
  • I must say that your article on geting pink colors from Chrome and Tin had an appealing writing style and was very informative.
  • I am very delight about the services provided by your site. It is really very informative.
  • This is a excellent site for Ceramic colors and containing very good knowledge for Ceramic coloring agents. Thank to Digitalfire Ceramic Oxides Directory.
  • Thanks for the fantastic program and service.
  • I have been in this ceramic line with 15 years experience covering the idustires right from porcelain insulators,vitrified tiles etc., With the help of chemistry graduation I started my career in the cermaic industry. This website is very much helpful in fine tuning and upgrading my experience with enhanced knowledge of ceramics.

What people have said about Insight-Live

  • Absolutely love the insight-live web app.
  • This article on porcelain is terriffic. I've been slip casting my own porcelain formula for nearly 40 years, and wish I had read it way back when I was first starting out! You provide exceedingly useful information- especially pertaining to the difficulties of trying to maintain consistency in a world of materials that are changing rapidly or disappearing entirely!
  • We love your work with Digital Fire. You've single handedly breathed life into many, many ceramics companies through your generous approach to sharing information. I can't tell you how valuable we have found your content to be. Thank you.
  • I am a potter of over ten years and am now in this year paying attention to my glazes and what goes in to them. It's been an awesome journey with plenty of "ah ha" moments and exponentially more "what the..." moments. Regardless of what I'm feeling, digital fire is so far the best resource I've encountered. I’ve been going about glazes all wrong, following recipes and stabbing in the dark hoping to find one that Works for me... well, it’s not working! I’m devoting my time to explore glaze chemistry even more than I have and to do this I am convinced I can not go forward efficiently without a test kiln. THANK YOU for these wonderful resources!
  • Thanks! I look forward to seeing your posts. I have read and printed many things you have posted over many years. Have learned a lot from you.
  • I have found your website to be extremely helpful because of your analysis of glaze chemistry and other information too. I have been able to mix all my own glazes and troubleshoot with the information you provide. I want you to know how much you're helping fellow potters all over the country and I truly appreciate your generosity in sharing the information.
  • Thank you for this web site. Really thank you. I live in fear that it will disappear one day, so don’t ever delete it please!



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

1