Glaze

Deflocculant Dosage Calculator

Calculate starting amounts of sodium silicate or Darvan for deflocculating casting slip.

Reviewed by ClayCalc Editorial · Updated

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How Deflocculants Work

Clay particles carry a negative surface charge. In water, they attract and cluster together (flocculate), producing a thick gel. Deflocculants introduce excess negative ions (Na⁺ from silicate/soda ash, or polyacrylic chains from Darvan) that adsorb onto the clay surface, causing repulsion between particles and allowing the slip to remain fluid with much less water.

The result: casting slip flows freely at SG 1.78–1.82 instead of needing SG < 1.40 for pourable consistency, producing stronger, denser cast ware with lower shrinkage.

Titration Procedure

  1. Mix dry materials with the calculated water amount
  2. Add the starting deflocculant dose (from this calculator)
  3. Mix 5 minutes, test SG and flow
  4. Add 0.05% increments until maximum fluidity is reached
  5. Stop before the slip starts to thicken again (over-deflocculation)

Method & review note

About this calculation

Performs recipe and slurry arithmetic. A calculated percentage or expansion estimate cannot establish glaze durability, fit, toxicity, or food-contact suitability.

Reference: Digitalfire — Ceramic Glaze. See the editorial methodology for testing, precision and corrections.

Input handling: Values are sent to the ClayCalc server for this request and are not written to the application database.

Read the Glaze Testing Workflow

Frequently Asked Questions

What does a deflocculant do? expand_more
Deflocculants reduce the attraction between clay particles, allowing them to remain suspended with less water. This creates a fluid casting slip at a low water content, resulting in stronger cast pieces with lower shrinkage.
Why should I use both sodium silicate and soda ash? expand_more
They work synergistically. Sodium silicate provides the primary deflocculation through sodium ions and silicate anions. Soda ash raises pH and adds sodium ions. Together they achieve better deflocculation than either alone.
What is over-deflocculation? expand_more
Over-deflocculation (too much deflocculant) paradoxically causes the slip to thicken and gel. Add deflocculant in small increments (0.05% at a time) and always test viscosity before adding more.