Notes
Dextrin is a water-soluble carbohydrate derived from starch (usually corn or potato) and is used in ceramic slurries, glazes, and engobes as a temporary binder, thickener, and suspension aid. It is also used as a binder in ceramic bodies. Unlike glycerine, which remains liquid, dextrin forms a hard, brittle film when dry, making it useful for specific ceramic applications.
In ceramic slurries dextrin:
1. Is a binder, holding ceramic particles together before firing, adding green strength and dry hardness.
3. Is a suspension aid, preventing the settling of heavier particles.
4. Is an adhesion promoter, helps slurries stick to surface (especially vertical).
5. Burns out cleanly, decomposing at ~350–500°F (175–260°C) without residue.
Common Uses of Dextrin in Ceramics
Casting Slips: Helps maintain slip viscosity and reduces cracking in dried molds. Typical Addition: 0.5–2% (by dry weight of clay).
Engobes & Slip Decoration: Improves brushability and adhesion on leather-hard or dry clay on high ball clay mixes. Typical Addition: 2–5% (of dry mix). Water: Adjust for creamy consistency.
Sprayable Glazes & Underglazes: Acts as a binder to help glaze adhere when sprayed. Typical Addition: 0.5–1.5% (avoids clogging nozzles).
Pressing Aids: Mixed with dry clay powder to improve compatibility.
Advantages Over Other Binders (Like Gum Arabic or CMC)**
-Cheaper than many synthetic binders.
-Less sticky than gum arabic, making it easier to rework.
-Hardens when dry, unlike glycerine (which stays tacky).
Disadvantages
-Can make slurries **too stiff** if overused.
-May require **defoaming agents** (since it can create bubbles).
How to Mix Dextrin into Ceramic Slurries
1. Dissolve in Warm Water (if using pure dextrin powder).
2. Blend with Dry Ingredients before adding water.
3. Adjust Consistency – More dextrin = thicker, harder dry film.
Troubleshooting Dextrin in Slurries
-Too Brittle (Cracks When Dry): Reduce dextrin (1–2% max) or add glycerine (e.g. 0.5%)
-Poor Adhesion: Increase dextrin slightly (3–5%) or add a small amount of gum arabic.
-Slow Drying: Use less dextrin or ensure proper ventilation.
-Foaming/Bubbles: Add a drop of defoamer or let slurry sit before use.
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Dextrin is used in adhesives, thickening agents, paper sizing, textiles, printing inks, substitutes for lactose, felt manufacture, and in pyrotechnics. You can make your own dextrin using instructions found on youtube.com. To find a commercial source, google the phrase "dextrin data sheet".
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