01 / THE FUNDAMENTALSStart thick. Adjust gradually.
A correctly mixed glaze stays moderately suspended between uses, applies at roughly 0.4 mm wet thickness with a 1–2 second dip, and has a smooth, creamy consistency, a little thinner than drinking yoghurt.
Balance enough water for the glaze to dip and flow with little enough water for the solids to stay suspended. The less water in the mix, the better the suspension prospects.
Approach the target from the thick side. Add water gradually so you can stop as soon as the glaze reaches its working consistency.
02 / STARTING POINTA baseline, not a fixed recipe.
The general baseline is 1 litre of water per 1 kilogram of dry glaze. Crackle glazes typically need less. Start below the baseline and adjust using consistency, specific gravity and a test dip together.
For a 1 kg batch, begin with roughly 800 mL of water. The target specific gravity is generally 1.40–1.50, depending on the glaze.
03 / INITIAL MIXINGFrom dry powder to a working glaze.
- Weigh the dry glaze. For a 1 kg batch, start by adding the glaze to roughly 800 mL of water, rather than the full baseline litre.
- Mix thoroughly. At this ratio the glaze will almost certainly be thick, gluggy and unsuitable for dipping. That is expected.
- Add water in small increments. Mix between additions until smooth and creamy, a little thinner than drinking yoghurt. Adding water loosens an over-thick mix.
- Sieve before measuring. Undissolved lumps can skew the specific-gravity reading.
- Check specific gravity and test dip. Use the target range in Section 04, then dip a shard or low-value piece for 1–2 seconds. Inspect wet coverage and drying rate. Glazes that are very slow to dry usually need more water.
- Record the result. Log the working ratio and test results against the glaze before using the batch on production ware.
04 / SPECIFIC GRAVITYMeasure the mix.
Specific gravity (SG) compares the weight of mixed glaze with the weight of the same volume of water.
- Use a graduated cylinder or consistent container. Mark the level that holds exactly 100 g of water, excluding the container’s weight.
- Empty the water, tare the container and fill with sieved glaze slip to the same line.
- Divide the net glaze weight in grams by 100.
150 g ÷ 100 g = SG 1.50
SG is a ratio without units. In this example, the equivalent glaze density is approximately 1.50 kg/L.
Little or no frit
For a raw glaze, aim for roughly 1.40–1.42 SG.
High-frit glaze
The target may be as high as 1.45–1.50 SG.
Too low: the mix is thin or watery and may not gel or hold thickness. Too high: it applies too heavily or does not flow off evenly.
05 / CONSISTENCY & FLOCCULANTSGet the water right first.
Poor suspension or rapid separation almost always points to too much water in the mix. Solids cannot stay suspended in excess water: correct the water ratio first.
If the glaze still settles poorly at the correct water ratio and SG, a flocculant can help develop thixotropy: a gel structure that flows while stirred or dipped through, then sets within a second or two when still, helping the glaze cling without running or dripping.
Epsom salts
Use magnesium sulfate as a saturated solution prepared in a small plastic jar. The SOP gives a dosing range of one teaspoon to one tablespoon per 5 L bucket, added incrementally.
Vinegar
Add acetic acid (vinegar) a capful at a time directly to the mixing glaze. Get the SG right first: otherwise it can gel at the wrong thickness.
The bounce-back test
- With the mixer running, add the flocculant in small increments.
- After each addition, switch the mixer off and count the seconds until the surface stops moving and sets.
- Aim for approximately 2 seconds. Confirm on a shard or low-value piece and record the dose.
Under-flocculated: the glaze will not set and runs off the dipped piece. Over-flocculated: it sets too fast and thick, or will not pour and screen cleanly.
Dose against a test, not a recipe. Bounce-back time is a mixing-bucket test of the glaze itself. It is separate from dip time, which is how long you hold a piece beneath the surface.
06 / RECOVERYRecover a settled or hard-panned glaze.
Do not stir a hard-panned bucket.
If the glaze has a hard cake at the bottom and clear water on top, mixing it directly will not work and risks damaging the mixer or bucket. Follow this sequence.
- Pour off the clear water into a separate container. Keep it: you will need to add some back.
- Break up the hardened sediment with a spatula or scraper into small pieces.
- Redisperse using about half the reserved water. Mix until smooth, thick and well suspended.
- Add back the remaining water gradually, testing after each addition until the creamy target consistency is reached. You will almost certainly not need all of it.
- Pass through an 80-mesh (80#) sieve once fully redispersed and smooth.
- Re-test on a shard and log the result before glazing production ware.
Prevent hard panning next time: sieve before storage and use a correctly dosed flocculant, such as Epsom salts or vinegar. Both reduce how hard a glaze pans on standing; neither replaces the recovery sequence once panning has happened.
07 / PER-GLAZE LOGMake the next batch repeatable.
Record each glaze’s working ratio once established, and update the record whenever the ratio changes. Print this page to use the blank log below.
Working glaze record · water ratio is per weight of dry glaze
| Glaze |
Water : glaze |
Specific gravity |
Flocculant & dose |
Bounce-back |
Dip time |
| e.g. Abbots Cone 6 Transparent |
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Adapted from the Abbots Glaze Mixing SOP. The source SOP credits Tony Hansen’s “How to Gel a Ceramic Glaze” (Digitalfire / YouTube) for the SG measurement, vinegar flocculation and bounce-back guidance.
