There are so many things a melt flow tester can tell you

For any potter or hobbyist, making your own molds and slip casting presents amazing options. Making this melt fluidity tester will get you started in 3D printing, pouring plaster to make a mold and slip casting. These will help you understand glazes, including commercial ones, much better.

Consider how these melt flow tests demonstrate performance: Is a new brand-name material the same (e.g. tin oxide, feldspar, dolomite, Alberta slip)? Does a glaze recipe pass a sanity check? Is a batch of frit bad? Is a frit better for sourcing B₂O₃ than Gerstley Borate? Is a glaze matte because it is not melting enough? Is a glaze too reactive? Is a manufacturer's claim correct? Will a stain or metal oxide addition make my glaze melt more or less? Does a material substitute work as well as the original? How does a frit soften and melt over a range of temperatures? Do glazes of the same chemistry but different recipe really melt the same? Is this glaze prone to bubbling? Does a glaze melt have high surface tension?

Here is what you need: A geeky family member having a 3D printer, a blender, powdered slip casting clay, deflocculant, plaster and a 2000g 0.1g scale. This page is the "Next" button to get started. Everything you need to know is here.

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Downloadable 3D model for melt flow tester block mold

Available on the Downloads page

3D rendering of Fusion 360 drawing of glaze melt fluidity tester

This picture has its own page with more detail, click here to see it.

This is a 3D rendering of our melt fluidity tester. We have promoted this device for many years as an effective way to compare fired glaze properties (e.g. melt fluidity, surface tension, bubble retention, crystal growth, transparency, melting range, etc). Open the 3MF file in your slicer, move all pieces off the print bed and unselect them all. Then, print each part by moving it onto the bed and using place-on-face to orient it right. Print the funnel wide-side down with brim. Insert the natch clips and embeds into the holes, pour in the plaster, let it set and finally remove the PLA with a heat gun. You now have a working mold to make slip cast testers. Glue the natches and spacers into the embeds, strap the mold together, glue in the pour spout with slip and finish by filling the mold with slip. If the mold is dry, 10-15 minutes should be enough to get adequate thickness (don't make them too heavy). With 0.8mm thick walls, this drawing 3D prints quickly and is easy to remove when the plaster has set (using a heat gun). The halves interlock using natches (requiring our embeds and related parts). The mold halves can also be lined up by the outer edges before clamping them together (thus not requiring natches).

The 3D model of a new melt flow tester mold

This picture has its own page with more detail, click here to see it.

The two pieces print as shown (top left). Since the walls are thin they may bulge a little when plaster is poured in, this is a trade-off for their light weight. The back section prints with no support, the front one needs support turned on. The file is in 3MF format, this enables including all pieces in one file (STL format does not permit that). All modern slicers can handle 3MF and they enable individually placing and orienting each piece (it is best to print them separately).

Plaster: Do not to forget to insert the clips and embeds into the holes before pouring the plaster. The mold volume is 1750cc. According to the https://plaster.glazy.org calculator, 1370g water and 1960g potters plaster are needed. You may like to mix 300:210g of plaster:water first (in a large paper cup) and pour that into the bottoms, this assures no leaking or deformation during the main pour.

Finish: Use a heat gun to peel off the PLA shell. Dry the mold and flatten the matting faces on sandpaper if needed. Then, insert the natches and spacers into the embeds. Strap the halves together, insert the pouring spout and pour in the casting slip (use a slip intended for the temperature you fire at).

Flow tester model you can 3D-print yourself

Available on the Downloads page

This picture has its own page with more detail, click here to see it.

This is not the mold, this is a model of what the mold enables you to make out of clay. Your printer should be able to make this with no support and no infill since there are no extreme overhangs (configure the slicer accordingly). This can be useful as a demonstration. It prints quickly and takes only 47g of PLA filament. It is 10% larger than fired testers will be.

3D is not too complicated!

Download and print something as a first step.

This picture has its own page with more detail, click here to see it.

3D design and printing is so valuable in ceramics that we can't stop pushing it. Here is how one goes about 3D printing a 3MF model file downloaded from this site. Why 3MF? Unlike the much older STL format, it enables multiple objects, units of measure and meta information. If you are on the page hosting this image, there is a link to the five-minute tutorial video at the bottom (otherwise click the image).

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A Low Cost Tester of Glaze Melt Fluidity
Use this novel device to compare the melt fluidity of glazes and materials. Simple physical observations of the results provide a better understanding of the fired properties of your glaze (and problems you did not see before).

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