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MGBase3 - General Purpose Glossy Base 1 (Mastering Glazes)

Modified: 2026-06-02 20:15:54

From page 92 in Mastering Glazes book

Notes

In Mastering Cone 6 Glazes, the Glossy Clear Liner is meant to stay clear. This base is adapted to being a foundation for color experiments using oxides and stains.

Key Properties
• Visual Appearance: In its base form, it is a clean, transparent-to-translucent gloss. It is slightly more "active" than the Liner glaze, having a bit more depth and fluid character.
• The Science: It is a Calcium-Alumina-Silicate glaze. It accepts colorants more vibrantly, especially Chrome, Cobalt, Copper, and Iron.
• Surface: High-gloss and reflective. It creates a "wet look" that can make colors pop and appear more saturated.
• Versatility: It is stable enough for functional ware but responsive enough to be used for decorative layering.

Likes (Pros)
• A "Canvas": This is the best recipe in the book for creating your own "house colors."
• Excellent Melt: It has a very reliable melt at Cone 6. It flows just enough to smooth out any brush strokes or uneven dipping marks.
• Strong Color Development: It doesn't "muddy" colors. Blues come out crisp, and greens come out bright.
• Durability: It meets the authors' standards for stability and acid resistance, making it suitable for the outside (and often inside) of dinnerware.

Dislikes (Cons)
• Crazing Risk: Like many glossy glazes, it has a moderate thermal expansion.
• Thickness Sensitivity: While it isn't as runny as Waterfall Brown, it is more mobile than the High Calcium Mattes.
• Bubbling on Dark Clays: On certain dark, gas-heavy clay bodies, this can occasionally trap "off-gassing" bubbles, resulting in tiny pinholes if the kiln isn't soaked at the peak temperature.

My Comments:
This has a high MgO content (from significant talc), so it could lose some gloss if the kiln is cooled slowly.

Related Information

A transparent glaze is going satin:

Is it the feldspar and kaolin substitutions?

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

A potter reports that a switch from G-200 feldspar to Mahavir, and EPK to Imerys kaolin, has resulted in this transparent glaze becoming more satin. Is that possible? Yes. Because this glaze is on a unity formula tipping point.

To see it, you do not need to know how to do glaze chemistry, just how to display the calculated unity formulas side-by-side. My Insight-live shows them here. The material change has little effect. But there is an anomaly: 0.29 MgO. That is magnesia matte territory. The MgO is very likely there to help bring the thermal expansion as low as possible (to avoid crazing). For people who cool their kilns relatively quickly, this fires glossy. But a material change could well affect the cooling rate needed to maintain the gloss. That being said, the potter may also be firing slower, yet attributing the mattness to the materials. Or it could be a combination of both.

This is a popular glaze, among others in the book "Mastering Glazes". In Ron Roy's circumstances, and for many others, it is glossy. But for this potter, a small change (in the recipe materials and also likely in firing) has produced this issue.

Gemini describes a pottery glaze recipe like a salesman

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

This is 2026. It uses expressions like "designed for performance", "specifically engineered", "perfectly transparent", "strict limit formulas", "perfect balance", and "ultimate". Really? Doesn't calling a recipe "ultimate" suggest that if one has an issue with it, then the problem is automatically with them, not the recipe? No. Consider:

-Glazes are systems, not recipes. They have many mixing, application, drying, firing, surface and aesthetics properties that interrelate. Add to that cost, material availability and consistency, material solubility, changes with aging and microbial response. These properties all play against each other; if you want one, you have to give up another. You can optimize some of them at the expense of others.
-Non-recipe factors, like firing method and schedule, application methods, body or engobe or slip underneath, and mixing methods, can really affect performance.
-The only recipe that is perfect for you is the one you develop and fine-tune to have the property pluses that favour your priorities and the faults that match what you can tolerate. The expression "perfect balance" thus applies only to Ron Roy who formulated it.

One more reason to become your own glaze engineer.

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XML to Paste Into Insight-live

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